Evaluation method for voltage imbalance of network tracking / constructing type hybrid wind power collection system

Abstract

The invention discloses a method for evaluating voltage unbalance of a following / construction network type hybrid wind power collection system. The method is suitable for a hybrid wind power plant grid-connected scene comprising a construction network type converter (GFM) and a following network type converter (GFL). The method comprises the following steps: firstly, constructing fundamental frequency negative sequence impedance models in different access modes, and establishing a negative sequence equivalent circuit model by combining system electrical topology; secondly, the voltage unbalance degree of each confluence node is calculated through sequence component analysis; secondly, analyzing the influence rule of factors such as the number proportion of the network-forming type units, the access voltage level and the space layout on the voltage imbalance; and finally, verifying the evaluation method through a power system simulation platform to ensure the accuracy and applicability of the result. The method can be used for electric energy quality evaluation and optimal configuration analysis under the regional-level and multi-wind-power-plant grid-connected condition.

Description

Technical Field

[0001] This invention relates to the field of new energy grid connection and power quality assessment technology, and in particular to an assessment method for voltage imbalance in a hybrid wind power collection system with integrated / grid connection. Background Technology

[0002] The wind power aggregation system is a crucial link in connecting the output power of multiple wind farms to the high-voltage power grid via a step-up transformer. Its operational stability directly affects the safe grid connection and power quality of large-scale wind power projects. During grid-connected operation, three-phase voltage balance is essential for ensuring normal equipment operation. Excessive voltage imbalance can lead to a series of adverse consequences, including equipment overheating, reduced efficiency, and malfunctioning protection systems. Grid-connected converters (GFMs) and grid-linked converters (GFLs) are currently the mainstream grid-connected control methods for wind turbines, but they differ significantly in dynamic characteristics and grid adaptability. When GFMs and GFLs are mixed, the negative-sequence impedance characteristics and voltage response patterns of the system change, thus affecting the three-phase voltage balance.

[0003] Current research on voltage imbalance in wind power systems mainly focuses on analyzing grid-side factors in pure GFL (Ground-Floating Heat exchanger) scenarios or evaluating transient response characteristics under grid asymmetric fault conditions. While these methods have revealed some of the causes of voltage imbalance, a system modeling and analysis method for negative-sequence impedance changes after grid-connected converters has not yet been developed for hybrid wind power aggregation systems. Furthermore, existing literature primarily provides qualitative analyses of the quantitative impact of system-side factors such as the ratio of turbines, connection location, voltage level, and spatial distribution on voltage imbalance, lacking precise assessment methods that can be directly applied in the engineering planning stage.

[0004] In actual operation, the proportion and location distribution of grid-connected turbines in hybrid wind power aggregation systems have a significant impact on the voltage imbalance of the busbars. However, due to the lack of an effective evaluation method that can combine negative sequence impedance characteristics, electrical topology, and node voltage distribution for unified analysis, it is difficult to accurately predict the voltage imbalance trend under different configuration schemes during the design and operation phases. This lack of analytical capability introduces uncertainty and risks to system structure optimization and power quality management. Summary of the Invention

[0005] To address the problems of existing technologies, embodiments of the present invention provide a method for evaluating voltage imbalance in a hybrid wind power collection system with integrated wind power and grid connections. The technical solution is as follows: On the one hand, a method for assessing voltage imbalance in a hybrid wind power collection system with integrated wind power and grid is provided, including the following steps: Step 1: Construct a fundamental frequency negative sequence impedance model for the hybrid wind power aggregation system. The hybrid wind power aggregation system includes multiple wind turbine units connected to at least one type of grid-connected converter (GFM) and at least one type of grid-connected converter (GFL). The equivalent negative sequence impedance of various wind turbine units under different access methods is obtained through aggregation modeling. The overall fundamental frequency negative sequence impedance characteristics of the hybrid wind power aggregation system are determined by combining the electrical connection topology. Step 2: Establish the negative sequence equivalent circuit model of the hybrid wind power collection system. The negative sequence equivalent circuit model includes the grid equivalent negative sequence voltage source, the grid-side negative sequence impedance, the wind turbine-side negative sequence impedance and the negative sequence impedance of its connecting lines. Calculate the negative sequence voltage distribution of each collector node based on the series-parallel relationship. Step 3: Calculate the voltage imbalance of each bus node. The voltage imbalance is the ratio of the root mean square value of the negative sequence voltage component to the root mean square value of the positive sequence voltage component, which is used to evaluate the degree of voltage asymmetry of the system. Step four: Based on the modeling and calculation results of steps one to three, analyze the influence of wind turbine configuration parameters on voltage imbalance. The configuration parameters include the ratio of grid-connected and grid-linked turbines, their connection location, and spatial distribution characteristics, which are used to evaluate the changing trend and response characteristics of voltage imbalance under different configuration schemes.

[0006] Furthermore, the method for constructing the fundamental frequency negative sequence impedance model in step one includes: The grid-connected and grid-following wind turbines are grouped according to their access voltage level and spatial location. The same type of turbines is modeled as a combination of equivalent negative sequence voltage source and negative sequence impedance using the electrical equivalent aggregation method. The equivalent negative sequence impedance parameters of the hybrid wind power aggregation system are calculated by the series and parallel impedance relationships between the groups.

[0007] Furthermore, the construction of the negative-sequence equivalent circuit model in step two includes: Based on the electrical topology of the wind power collection system, each combiner node, wind turbine connection point, grid-side connection point, and transmission line between them are represented as electrical components with negative sequence impedance. The model includes at least the following: An external power grid equivalent negative sequence voltage source, the power grid equivalent negative sequence impedance connected in series with it, the equivalent negative sequence impedance of each wind turbine, and the negative sequence impedance of multiple transmission lines connecting the wind turbines and the combiner nodes are used to form a multi-node fundamental frequency negative sequence voltage network by analyzing the electrical connection relationship between each branch. This network is then used to calculate the distribution characteristics of the negative sequence voltage at each node.

[0008] Furthermore, the method for calculating the voltage imbalance in step three includes: The positive-sequence and negative-sequence components of the three-phase voltage at each bus node are extracted, and their root mean square values ​​are calculated respectively. The voltage imbalance is the ratio of the root mean square value of the negative-sequence voltage to the root mean square value of the positive-sequence voltage, which is used to characterize the degree of asymmetry of the three-phase voltage at the node. The larger the ratio, the more severe the voltage imbalance.

[0009] Furthermore, step four, which assesses the impact of key system-side factors on voltage imbalance, includes: Several representative configuration schemes were selected, and the proportion, connection location and spatial distribution of grid-connected wind turbines were changed respectively. Based on the negative sequence equivalent circuit model and voltage imbalance calculation, the quantitative influence relationship of each configuration parameter on the voltage imbalance of the combiner node was analyzed, and a multi-dependent variable correlation model between system configuration and imbalance was formed to assist in optimizing the structural design of wind power system.

[0010] Furthermore, the multi-dependent variable association model combines the spatial distribution of wind turbine units with the access level of grid-connected converters to construct combined scenarios of different spatial deployment strategies and access methods. It compares and analyzes the marginal impact characteristics of near-end and far-end wind turbine unit deployment on voltage imbalance under each scenario, and identifies the configuration strategy with the best voltage imbalance suppression effect.

[0011] Furthermore, it also includes a verification process for the evaluation method based on a power system simulation platform, the verification process including: A hybrid wind power collection system model containing grid-connected and grid-linked wind turbines was built in a power system transient simulation environment. The constructed negative sequence impedance model and equivalent circuit parameters were imported, and simulation tasks with different configuration scenarios were run. The voltage imbalance of the collector nodes under each configuration was dynamically monitored and compared to verify the accuracy of the evaluation method in predicting the voltage imbalance trend.

[0012] Furthermore, the hybrid wind power aggregation system is a regional-level power access system comprising multiple wind farms. Each wind farm is equipped with both grid-connected and grid-linked wind turbines. The evaluation method is applicable to aggregation structures where multiple wind farms are connected by transmission lines and share a high-voltage busbar to the main power grid. By calculating the negative sequence impedance of each wind farm cluster and their mutual coupling relationships, a unified evaluation and distributed configuration optimization of the voltage imbalance of each busbar node within the region can be achieved.

[0013] On the other hand, a computer-readable storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the method for assessing voltage imbalance in a grid-connected hybrid wind power collection system.

[0014] On the other hand, an electronic device is provided, including a processor and a memory, wherein the memory stores a computer program, which, when executed by the processor, is used to implement the voltage imbalance assessment method for the aforementioned grid-connected hybrid wind power collection system.

[0015] The beneficial effects of the technical solution provided by the embodiments of the present invention are as follows: This invention provides a method for assessing voltage imbalance in hybrid wind power collection systems (GF / GFL). By constructing a fundamental frequency negative sequence impedance model incorporating both grid-connected converters (GFM) and GFLs, and establishing a multi-node negative sequence equivalent circuit based on the system's electrical topology, the method can accurately characterize voltage imbalance characteristics under different access methods and parameter configurations. This method calculates voltage imbalance through standardized sequence component analysis, ensuring the assessment results are uniform and comparable, and facilitating direct application across different engineering scenarios.

[0016] This method comprehensively considers key system-side factors such as the proportion of generating units, the voltage level at which they are connected, and the spatial layout, enabling quantitative analysis and trend judgment of voltage imbalance in multiple scenarios. Compared to experience-based analysis methods that rely solely on a single operating condition, this method can accurately predict the voltage imbalance variation patterns of different configuration schemes during the planning and design phase, providing data support for wind power system structural adjustments.

[0017] Furthermore, this method, when used in conjunction with a power system simulation platform, enables the verification and visualization of the assessment process, ensuring consistency between the analysis results and actual system operation trends. This method possesses good versatility and scalability, applicable to power quality assessment under regional, multi-wind farm grid-connected conditions, and can provide reliable technical references for the optimized configuration, operation scheduling, and voltage support strategy formulation of wind power aggregation systems. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of 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 method for assessing voltage imbalance in a grid-connected hybrid wind power collection system, as described in an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of a typical scenario of wind power aggregator grid connection after GFM access according to an embodiment of the present invention; Figure 3These are schematic diagrams of the fundamental frequency negative sequence impedance models of wind farms under various scenarios in embodiments of the present invention; wherein, Figure (a) is a traditional GFL site; Figure (b) is scenario 1; Figure (c) is scenario 2; and Figure (d) is scenario 3. Figure 4 This is a typical electrical topology diagram of a wind power system according to an embodiment of the present invention; Figure 5 This is a schematic diagram of the equivalent circuit model of the fundamental frequency negative sequence of a wind power system according to an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the impact of key system-side factors in the scenario of modifying GFM wind turbines according to an embodiment of the present invention; wherein, Figure (a) shows the impact of the proportion of GFM wind turbines; and Figure (b) shows the impact of the site spatial layout. Figure 7 This is a schematic diagram illustrating the impact of adding GFM to a 35kV busbar in this embodiment of the invention on the number of GFM units. Figure 8 This is a schematic diagram illustrating the impact of key system-side factors in the scenario of installing GFM on a 220kV busbar according to an embodiment of the present invention; wherein, Figure (a) shows the impact of the number of GFM wind turbine units; and Figure (b) shows the impact of the site spatial layout. Figure 9 This is a flowchart illustrating the analysis method for voltage imbalance influencing factors and mechanisms in a hybrid wind power collection system based on a grid-connected system, according to an embodiment of the present invention. Figure 10 This is a schematic diagram of the voltage imbalance waveform when the number of GFM units is changed according to an embodiment of the present invention. Figure 11 The voltage imbalance waveform for changing the number of GFM units in an embodiment of the present invention; Figure 12 The voltage imbalance waveform for changing the number of GFM units is shown in an embodiment of the present invention. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0022] This invention provides a method for assessing voltage imbalance in a hybrid wind power collection system (including grid-connected systems). See [link to relevant documentation]. Figure 1 It includes the following steps: Step 1: Construct the fundamental frequency negative sequence impedance model of the hybrid wind power collection system; The hybrid wind power aggregation system includes multiple wind turbine units connected to at least one type of grid-connected converter (GFM) and at least one type of grid-connected converter (GFL). The equivalent negative sequence impedance of various wind turbine units under different access methods is obtained through aggregation modeling. The overall fundamental frequency negative sequence impedance characteristics of the hybrid wind power aggregation system are determined by combining the electrical connection topology. Specifically, the method for constructing the fundamental frequency negative sequence impedance model in step one includes: The grid-connected and grid-following wind turbines are grouped according to their access voltage level and spatial location. The same type of turbines is modeled as a combination of equivalent negative sequence voltage source and negative sequence impedance using the electrical equivalent aggregation method. The equivalent negative sequence impedance parameters of the hybrid wind power aggregation system are calculated by the series and parallel impedance relationships between the groups.

[0023] Step 2: Establish the negative sequence equivalent circuit model of the hybrid wind power collection system; The negative sequence equivalent circuit model includes the grid equivalent negative sequence voltage source, grid-side negative sequence impedance, wind turbine-side negative sequence impedance and the negative sequence impedance of its connecting lines, and calculates the negative sequence voltage distribution of each bus node based on the series-parallel relationship. Specifically, the construction of the negative-sequence equivalent circuit model in step two includes: Based on the electrical topology of the wind power collection system, each combiner node, wind turbine connection point, grid-side connection point, and transmission line between them are represented as electrical components with negative sequence impedance. The model includes at least the following: An external power grid equivalent negative sequence voltage source, the power grid equivalent negative sequence impedance connected in series with it, the equivalent negative sequence impedance of each wind turbine, and the negative sequence impedance of multiple transmission lines connecting the wind turbines and the combiner nodes are used to form a multi-node fundamental frequency negative sequence voltage network by analyzing the electrical connection relationship between each branch. This network is then used to calculate the distribution characteristics of the negative sequence voltage at each node.

[0024] Step 3: Calculate the voltage imbalance at each bus node; The voltage imbalance is the ratio of the root mean square value of the negative sequence voltage component to the root mean square value of the positive sequence voltage component, which is used to evaluate the degree of voltage asymmetry in the system. Specifically, the method for calculating the voltage imbalance in step three includes: The positive-sequence and negative-sequence components of the three-phase voltage at each bus node are extracted, and their root mean square values ​​are calculated respectively. The voltage imbalance is the ratio of the root mean square value of the negative-sequence voltage to the root mean square value of the positive-sequence voltage, which is used to characterize the degree of asymmetry of the three-phase voltage at the node. The larger the ratio, the more severe the voltage imbalance.

[0025] Step 4: Based on the modeling and calculation results of Steps 1 to 3, analyze the influence of wind turbine configuration parameters on voltage imbalance. The configuration parameters include the ratio of grid-connected to grid-connected units, their access locations, and spatial distribution characteristics, which are used to evaluate the voltage imbalance trend and response characteristics under different configuration schemes.

[0026] Specifically, step four, which assesses the impact of key system-side factors on voltage imbalance, includes: Several representative configuration schemes were selected, and the proportion, connection location and spatial distribution of grid-connected wind turbines were changed respectively. Based on the negative sequence equivalent circuit model and voltage imbalance calculation, the quantitative influence relationship of each configuration parameter on the voltage imbalance of the combiner node was analyzed, and a multi-dependent variable correlation model between system configuration and imbalance was formed to assist in optimizing the structural design of wind power system.

[0027] Furthermore, the multi-dependent variable association model combines the spatial distribution of wind turbine units with the access level of grid-connected converters to construct combined scenarios of different spatial deployment strategies and access methods. It compares and analyzes the marginal impact characteristics of near-end and far-end wind turbine unit deployment on voltage imbalance under each scenario, and identifies the configuration strategy with the best voltage imbalance suppression effect.

[0028] Furthermore, it also includes a verification process for the evaluation method based on a power system simulation platform, the verification process including: A hybrid wind power collection system model containing grid-connected and grid-linked wind turbines was built in a power system transient simulation environment. The constructed negative sequence impedance model and equivalent circuit parameters were imported, and simulation tasks with different configuration scenarios were run. The voltage imbalance of the collector nodes under each configuration was dynamically monitored and compared to verify the accuracy of the evaluation method in predicting the voltage imbalance trend.

[0029] Furthermore, the hybrid wind power aggregation system is a regional-level power access system comprising multiple wind farms. Each wind farm is equipped with both grid-connected and grid-linked wind turbines. The evaluation method is applicable to aggregation structures where multiple wind farms are connected by transmission lines and share a high-voltage busbar to the main power grid. By calculating the negative sequence impedance of each wind farm cluster and their mutual coupling relationships, a unified evaluation and distributed configuration optimization of the voltage imbalance of each busbar node within the region can be achieved.

[0030] To further refine the voltage imbalance assessment method for the hybrid wind power collection system described in this invention, and in conjunction with the analysis of the influencing factors and mechanisms of voltage imbalance in the system, the following will systematically explain the quantitative modeling and calculation process of key configuration parameters, electrical connection characteristics, and their impact on the voltage asymmetry of the combiner nodes, based on the access structure, electrical modeling principles, and negative sequence component analysis methods of grid-connected and grid-connected wind turbines. This will clarify the causal mechanism and variation law of voltage imbalance in the hybrid collection system.

[0031] The technical solution described in this invention is based on a systematic analysis of the influencing factors and mechanisms of voltage imbalance in grid-connected hybrid wind power collection systems. It proposes a quantitative method for evaluating the degree of three-phase voltage asymmetry in hybrid wind power access structures, aiming to clarify the influence path and laws of grid-connected wind turbines on the voltage imbalance characteristics of the busbar. To address the potential subsynchronous / supersynchronous oscillation risks of traditional GFL wind farms under weak grid conditions, a certain proportion of GFM units are considered for configuration within each farm to enhance voltage support capabilities and thus strengthen system stability. In hybrid wind farms with GFM access, typical scenarios for GFM converter connection locations can be roughly divided into three categories: Scenario ① converting some GFL units in the farm to GFM control; Scenario ② adding GFM units to the 35kV busbar inside the farm; Scenario ③ adding GFM units to the 220kV busbar connected outside the farm.

[0032] The above analytical method includes the following steps: Step 1: Establish the fundamental frequency negative sequence impedance of the hybrid wind power collection station (either based on the grid or the ground). Based on typical scenario classifications of GFM converter connection locations, the fundamental frequency negative sequence impedance of GFL / GFM hybrid wind power aggregation stations under different GFM connection locations is constructed. When a wind farm connects to GFM units, there are two different types of units within the station: GFL and GFM. For ease of analysis, the wind turbine units are first grouped, and the grouped units are then aggregated and equivalently evaluated. Based on the electrical interconnection characteristics between each group, the negative sequence impedance model of the entire wind farm station is constructed through the equivalent series and parallel relationships of the impedances of each branch. Figure 2 The fundamental frequency negative sequence impedance of wind farms in various scenarios is as follows: Figure 3 As shown in the figure, Z n GFL Z n GFM For a single GFL and GFM unit, the negative sequence impedance is Z. n L is the equivalent negative sequence impedance of the transmission lines and transformers between the wind farm and the corresponding busbars; n is the total number of wind turbines in each station.

[0033] (1) The negative sequence impedance of the wind farm in scenario 1 is: (1) In the formula, i represents the number of GFL wind turbines in the site, and the number of GFM wind turbines retrofitted in the site is ni; the superscript 1 represents scenario 1.

[0034] (2) The negative sequence impedance of the wind farm in scenario 2 is: (2) In the formula, m is the total number of wind turbines in the station after the installation of GFM, so the number of GFM wind turbines installed in the station is mn; the superscript 2 represents scenario 2.

[0035] (3) The negative sequence impedance of the wind farm in scenario 3 is: (3) In the formula, Z n L1 Z n L2 These are the negative sequence impedances of the transmission lines and transformers between the GFL and GFM wind farm turbines and the 220kV busbar, respectively; the superscript 3 represents scenario 3.

[0036] Step 2: Construct the negative sequence equivalent circuit model of the wind power collection system Select as Figure 4 The typical wind power collection system shown is used as the research object. In this system, two 220kV busbars 1 and 2 connect several wind farms respectively. The two busbars are connected by a transmission line and finally connected to the 500kV AC main grid via a step-up transformer. The negative sequence impedance of all wind farms connected to busbars 1 and 2 (i.e., wind power cluster 1 and wind power cluster 2) is modeled and analyzed.

[0037] according to Figure 4 By considering the series and parallel relationships of the impedances of each wind farm and the line impedance, the negative sequence impedances of wind power cluster 1 and wind power cluster 2 are derived as follows: (4) In the formula, Z n W express Figure 4 The negative sequence impedance of each wind farm is shown in the figure. The subscript number represents the wind farm number.

[0038] in accordance with Figure 4 The electrical topology construction of wind power systems, such as Figure 5 The fundamental frequency negative sequence equivalent circuit model is shown.

[0039] Figure 5 Middle,U n g Z is the equivalent unbalanced voltage source of the external power grid. ng Z is the equivalent negative sequence impedance of the power grid. n JQ1 Z n JQ2 Z represents the negative sequence impedance of wind power clusters 1 and 2. n Line For the line between two wind power clusters, U n MX1 U n MX2 I is the equivalent negative sequence voltage of busbars 1 and 2. n g This is the base frequency negative sequence current for wind power grid connection.

[0040] Step 3: Investigate the generation mechanism of bus voltage imbalance in the collection system. According to the definition in national standard GB / T15543, the expression for voltage unbalance is: (5) In the formula, U1 is the root mean square value of the positive sequence component of the three-phase voltage, in volts (V); U2 is the root mean square value of the negative sequence component of the three-phase voltage, in volts (V).

[0041] according to Figure 5 From the circuit diagram shown, the negative sequence voltage expressions for the 220kV busbars 1 and 2 of this system can be obtained respectively: (6) in As can be seen from equation (6), the fundamental frequency negative sequence voltage of the busbar is affected by the following factors, mainly including the unbalanced voltage source U of the power grid. n g The equivalent negative sequence impedance Z of the power grid n g Negative sequence impedance Z of transmission lines n Line Factors such as grid-side factors and the negative sequence impedance Z of wind power clusters 1 and 2 n JQ1 Z n JQ2 System-side factors, including grid-side factors which act as external excitations, are determined by the structural parameters and operating status of the external power grid. This invention will subsequently focus on system-side factors, primarily the impact of the negative-sequence impedance within the wind power system on the negative-sequence voltage of the busbar.

[0042] Step 4: Investigate the degree and pattern of the influence of key system-side factors on the voltage imbalance of the bus after GFM access.

[0043] The above analysis shows that the system-side factors affecting the voltage imbalance of the bus in various GFL / GFM hybrid wind power scenarios are mainly related to the negative sequence impedance Z of the wind power cluster. n JQ1 Z n JQ2 It is related to equations (1) to (3). From these equations, we can see that Z is determined... n JQ1 Z n JQ2 The main factors include the number of wind turbine units and their spatial layout, namely the number and ratio of GFL / GFM power sources, as well as the location of GFM access and the distribution of near and far wind farms. Based on the actual output power data of the wind farm, each wind farm has a total of 100 units, corresponding to a wind power cluster output power of 1500MW. The analysis reveals the impact of the main system-side factors on the voltage imbalance of bus 2 as follows: Figures 6-8 As shown: Depend on Figures 6-8 Analysis shows that increasing the proportion of GFM units in GFL / GFM hybrid wind farms has different effects on system voltage imbalance under different GFM unit layout locations: retrofitting GFMs will exacerbate the voltage imbalance of the busbar, and the impact is more significant in near-end wind farms; adding GFMs will reduce the voltage imbalance of the busbar, with the impact of adding GFMs to the 220kV busbar being greater than that to the 35kV busbar. Moreover, the more transmission lines of each wind farm with added GFMs, the smaller the voltage imbalance of the busbar, and the impact is also greater in near-end wind farms.

[0044] In summary, the specific process of the analysis method for voltage imbalance in a hybrid wind power collection system based on a grid-connected system proposed in this embodiment is as follows: Figure 9 As shown.

[0045] To verify the applicability and accuracy of the voltage imbalance assessment method for hybrid wind power collection systems with grid-connected and grid-connected wind turbines as described in this invention, a hybrid wind power collection system model containing grid-connected and grid-connected wind turbines was constructed using a power system simulation platform. Dynamic simulation analysis under different configuration scenarios was conducted to verify the effectiveness of the method in assessing the impact of voltage imbalance in wind power systems, as detailed below: Build in PSCAD / EMTDC Figure 4 The electromagnetic transient simulation model of the system is shown. The conclusions are verified by simulation. The voltage imbalance of the system's bus 2 is analyzed by the main factors such as the number of wind turbines and their spatial layout under various GFM access scenarios. The simulation verification results are as follows: Figures 10-12 As shown: Keeping the total number of wind turbines in the site constant at 600, initially setting the proportion of GFM turbines in the near and far wind farms at 20% for H1 and H2 respectively, the proportion of GFM turbines in the near and far wind farms is increased to 60% respectively. The voltage imbalance of bus 2 changes as follows: Figure 10 As shown, increasing the proportion of GFM units in near- and far-field wind farms increases the voltage imbalance of the busbar. Figure 10 It is evident that retrofitting GFM units in near-end wind farms has a greater impact on them, which is consistent with the theoretical analysis conclusions above.

[0046] Keeping the number of GFL units in the wind farm unchanged at 100, initially setting the number of GFM units installed on the 35kV bus to 10, increasing that number to 100, the corresponding GFM proportion J of the wind power cluster changes from 9.1% to 50%. The voltage imbalance of bus 2 changes as follows: Figure 11 As shown, increasing the number of GFM units installed on the 35kV busbar increases the voltage imbalance on the busbar. (Comparison) Figure 10 and Figure 11 It is evident that the addition of GFM units to the 35kV busbar has a minimal impact on the voltage imbalance of the busbar, consistent with the theoretical analysis conclusions above.

[0047] Keeping the number of GFL units in the wind farm constant at 100, simulations were performed to increase the GFM ratio of the wind power cluster K1 and K2 to 60% by adding near-end and far-end GFM units to the 220kV busbar, and the number of transmission lines was increased accordingly. The voltage imbalance of the corresponding busbar 2 was then simulated as follows. Figure 12 As shown. Increasing the number of GFM units installed on the 220kV bus and the number of transmission lines reduces the voltage imbalance of the busbar. Figure 12 It can also be seen that the installation of GFM units in the near-end wind farm has a greater impact on it, which is consistent with the theoretical analysis conclusions above.

[0048] In summary, the voltage imbalance assessment method for hybrid wind power collection systems proposed in this invention combines modeling the influence of wind turbine type, grid topology, and electrical parameters on the negative sequence impedance characteristics of the system. It establishes a system-level negative sequence equivalent circuit model and a quantitative analysis framework for voltage imbalance indices. Simulations under multiple configuration scenarios verify the effectiveness and applicability of this method in identifying imbalance influencing factors and supporting optimized configuration design. The method possesses good versatility and engineering scalability, providing theoretical basis and technical support for the planning, design, and operational evaluation of practical wind power collection systems.

[0049] In some embodiments, a computer-readable storage medium is provided, on which a computer program is stored. When executed by a processor, the program is used to implement the steps of the voltage imbalance assessment method for a hybrid wind power collection system described in this embodiment of the invention. The program may include functional modules such as: constructing a fundamental frequency negative sequence impedance model of the hybrid wind power system, establishing a negative sequence equivalent circuit model, calculating the voltage imbalance degree of the collector node, analyzing the influence of wind turbine configuration on the imbalance degree, and generating a multivariate analysis report of the assessment results. This supports the automatic identification and quantitative evaluation of voltage asymmetry risks under different system structures and access strategies.

[0050] In other embodiments, an electronic device is proposed, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the program, it implements the steps of the voltage imbalance assessment method for a grid-connected hybrid wind power aggregation system as described in this embodiment of the invention. The electronic device can be a power system modeling and analysis platform, a new energy system operation assessment terminal, or an edge operation and maintenance module with electrical simulation computing capabilities. It can perform integrated operations such as constructing a system topology model, automatically identifying wind turbine types and access parameters, dynamically simulating negative sequence voltage response, and outputting voltage imbalance indicators, thereby improving the intelligence level of wind power system structural design and access planning.

[0051] The embodiments of the present invention may also include, but are not limited to, the forms described above. The computer program can be deployed on an industrial control server, a power grid dispatch center master station simulation platform, or a new energy equipment operation and maintenance terminal to realize a systematic analysis and evaluation of the voltage support capability of grid-connected converters in multi-new energy power station access scenarios, and has good versatility, portability, and engineering scalability.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for evaluating voltage imbalance of a follow-the-sun / meshed hybrid wind power collection system, characterized in that, The method comprises the following steps: Step one, constructing a fundamental frequency negative sequence impedance model of a hybrid wind power collection system, the hybrid wind power collection system comprising a plurality of wind power generators connected to at least one type of grid-forming converter and at least one type of grid-following converter, obtaining equivalent negative sequence impedance of each type of wind power generator under different access modes through aggregated modeling, and determining overall fundamental frequency negative sequence impedance characteristics of the hybrid wind power collection system in combination with an electrical connection topology; Step two, establishing a negative sequence equivalent circuit model of the hybrid wind power collection system, wherein the negative sequence equivalent circuit model comprises a grid equivalent negative sequence voltage source, a grid-side negative sequence impedance, a wind power generator-side negative sequence impedance, and a negative sequence impedance of a connecting line, and the negative sequence voltage distribution of each bus is calculated according to a series-parallel relationship; Step three, calculating a voltage unbalance degree of each bus, the voltage unbalance degree being a ratio of a square root mean value of a negative sequence voltage component to a square root mean value of a positive sequence voltage component, and being used for evaluating a voltage asymmetry degree of the system; Step four, based on modeling and calculation results of steps one to three, analyzing influence rules of wind power generator configuration parameters on voltage unbalance, the configuration parameters comprising a quantity ratio of grid-forming and grid-following generators, an access position, and a spatial distribution characteristic, and being used for evaluating variation trends and response characteristics of voltage unbalance under different configuration schemes.

2. The evaluation method according to claim 1, characterized in that The method of step one comprises: Grouping grid-forming and grid-following wind power generators according to access voltage levels and spatial positions, modeling the same type of generators into a combined model of an equivalent negative sequence voltage source and a negative sequence impedance by using an electrical equivalent aggregation method, and calculating equivalent negative sequence impedance parameters of the overall hybrid wind power collection system through a series-parallel impedance relationship between groups.

3. The evaluation method according to claim 1, characterized in that The method of step two comprises: Based on an electrical topology structure of the wind power collection system, representing each bus, a wind power generator access point, a grid-side connection point, and a power transmission line therebetween in the model as electrical elements containing negative sequence impedances, the model at least comprising: An external grid equivalent negative sequence voltage source, a grid-side equivalent negative sequence impedance connected in series with the external grid equivalent negative sequence voltage source, equivalent negative sequence impedances of the wind power generators, and a plurality of power transmission line negative sequence impedances connecting the wind power generators and the buses, forming a fundamental frequency negative sequence voltage network of multiple nodes by analyzing electrical connection relationships between branches, and being used for calculating distribution characteristics of negative sequence voltages of the nodes.

4. The evaluation method according to claim 1, characterized in that The method of step three comprises: Extracting positive sequence components and negative sequence components of three-phase voltages at each bus, respectively calculating square root mean values of the positive sequence components and the negative sequence components, and the voltage unbalance degree being a ratio of the square root mean value of the negative sequence voltage to the square root mean value of the positive sequence voltage, and being used for representing an asymmetry degree of the three-phase voltages at the node, and the greater the ratio, the more serious the voltage unbalance degree.

5. The evaluation method according to claim 1, characterized in that The method of step four comprises: A plurality of representative configuration schemes are selected, the proportion of grid-connected wind turbine generators, the access position and the spatial distribution mode are changed respectively, on the basis of the negative sequence equivalent circuit model and the voltage unbalance degree calculation, the quantitative influence relationship of each configuration parameter on the voltage unbalance degree of the bus node is analyzed, a multi-dependent variable correlation model between system configuration and unbalance degree is formed, which is used to assist in optimizing the structure design of the wind power system.

6. The evaluation method according to claim 5, characterized in that The multi-dependent variable correlation model combines the spatial distribution position of the wind turbine generator and the access level of the grid-connected converter, constructs the combination scene of different spatial layout strategies and access modes, compares and analyzes the marginal influence characteristics of the near-end and far-end wind turbine layout on the voltage unbalance degree in each scene, and identifies the configuration strategy with the optimal voltage unbalance suppression effect.

7. The evaluation method according to claim 1, characterized in that The evaluation method further includes a verification process based on a power system simulation platform, and the verification process includes: A hybrid wind power collection system model containing grid-connected and grid-following wind turbine generators is built in a power system transient simulation environment, the negative sequence impedance model and the equivalent circuit parameters are imported, a plurality of simulation tasks of different configuration scenes are run, the voltage unbalance degree of the bus node under each configuration is dynamically monitored and compared and analyzed, so as to verify the prediction accuracy of the evaluation method on the voltage unbalance trend.

8. The evaluation method according to claim 1, characterized in that The hybrid wind power collection system is a regional power access system containing a plurality of wind farms, each wind farm is configured with grid-connected and grid-following wind turbine generators, the evaluation method is suitable for a collection structure in which a plurality of wind farms are connected through transmission lines, share a high-voltage bus and are connected to the main grid, by calculating the negative sequence impedance of each wind farm cluster and their mutual coupling relationship, the voltage unbalance degree of each bus node in the region is uniformly evaluated and distributedly configured and optimized. 9.A computer readable storage medium having a computer program stored thereon, wherein the computer program, when executed by a processor, implements the evaluation method of voltage unbalance of the grid-following / grid-connected hybrid wind power collection system according to any one of claims 1 to 8. 10.An electronic device comprising a processor and a memory, wherein the memory stores a computer program, and the computer program, when executed by the processor, is used to implement the evaluation method of voltage unbalance of the grid-following / grid-connected hybrid wind power collection system according to any one of claims 1 to 8.

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