Voltage harmonic distortion distributed governance method and system suitable for low-voltage distribution network

Abstract

This invention belongs to the field of distribution network operation and management technology, and provides a distributed governance method and system for voltage harmonic distortion in low-voltage distribution networks. It constructs a three-level distributed governance architecture for voltage harmonic distortion, with a smart fusion terminal, a smart IoT meter, and a smart meter as the core components. In the third level, the smart fusion terminal divides the distribution network into zones. In the second level, the smart IoT meter performs simplified modeling of the zones. The third level issues a voltage harmonic distortion governance enable command to the zone with the most severe distortion. In the first level, the smart meter in the zone with the most severe problem models the harmonic coupling characteristics of the distributed source-load nodes. In the second level, the smart IoT meter solves and executes the governance decision, determining whether to terminate the governance based on the degree of voltage harmonic distortion in each zone. This invention solves the voltage harmonic distortion problem in distribution networks through a distributed governance model, with lower requirements for data transmission and processing capabilities, and is suitable for low-voltage distribution network scenarios.

Description

Technical Field

[0001] This invention belongs to the field of power distribution network operation and control technology, specifically relating to a distributed management method and system for voltage harmonic distortion in low-voltage power distribution networks. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] With the widespread integration of power electronic devices such as distributed photovoltaics and energy storage, voltage harmonic distortion in low-voltage distribution networks is becoming increasingly severe. The rapidly increasing capacity of power electronic devices and the more pronounced harmonic coupling characteristics of the sets of devices connected to each node further limit the speed and accuracy of voltage harmonic distortion mitigation decisions. Furthermore, voltage harmonic distortion mitigation requires comprehensive consideration of the relationships between multiple nodes and multiple frequencies of voltage and current in the distribution network. However, due to operational costs, the management equipment and hardware conditions of low-voltage distribution networks are relatively weak, and data acquisition, interaction, and processing capabilities are very limited. Therefore, mitigating voltage harmonic distortion in low-voltage distribution networks remains a significant challenge.

[0004] Currently, in the research and engineering application of voltage harmonic distortion mitigation, the traditional method involves configuring active power filters on large harmonic sources to emit harmonic currents that are equal in magnitude and opposite in direction to the harmonic currents emitted by the sources. In contrast to this "point-to-point" mitigation model, some small distribution networks employ a centralized "point-to-network" approach to voltage harmonic distortion mitigation. This centralized method can effectively solve voltage harmonic distortion problems when data is complete and communication conditions are good. The inventors have discovered that most rural low-voltage distribution networks are connected to large-scale distributed sources and loads, but hardware control conditions and data interaction and processing capabilities are very weak. Existing methods are difficult to apply effectively under these constraints. If the limitations and mitigation needs of low-voltage distribution networks are not fully considered, and a voltage harmonic distortion mitigation method suitable for this scenario is not proposed, it will be difficult to solve the voltage harmonic distortion problem, thereby limiting the safe and stable power supply in rural areas. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a distributed method and system for managing voltage harmonic distortion in low-voltage distribution networks. This invention effectively manages voltage harmonic distortion issues.

[0006] According to some embodiments, the present invention adopts the following technical solution: A distributed method for voltage harmonic distortion mitigation in low-voltage distribution networks includes the following steps: A three-tier distributed governance architecture for voltage harmonic distortion is constructed. The first tier includes several smart meters, the second tier includes several smart IoT meters, and the third tier includes several smart converged terminals. Obtain the node relationships and impedance relationships in the distribution network, and perform clustering of each node according to the mutual impedance relationship between nodes to obtain the distribution network partitioning results; Obtain the node impedance and current information within the partition, perform simplified modeling within the partition, and upload it to the intelligent fusion terminal; Obtain the total harmonic distortion rate of voltage at each node in the distribution network, construct a governance priority sequence, and output a voltage harmonic distortion governance enable command to the zone with the most severe voltage harmonic distortion problem. In response to the voltage harmonic distortion mitigation enable command, the smart meters in the first-level partition with the most severe voltage harmonic distortion problem acquire the voltage and current data of the node and perform harmonic coupling characteristics modeling for the distributed source and load of the node. In response to the voltage harmonic distortion mitigation enable command, the second-level smart IoT meter, combined with other simplified partition models, constructs a distribution network model. Taking into account the harmonic coupling effects of distributed source loads connected to nodes within the partition, it solves the voltage harmonic distortion mitigation decision for a single partition and controls the active power filter to perform voltage harmonic distortion mitigation within the partition.

[0007] As an alternative implementation method, the process of obtaining node relationships and impedance relationships in the distribution network, and clustering each node according to the mutual impedance relationship between nodes to obtain the distribution network partitioning results includes: establishing a node impedance matrix at each frequency based on the impedance information between each node in the distribution network; and proposing a comprehensive mutual impedance coefficient to characterize the impedance relationship between nodes at multiple frequencies. :

[0008] In the formula, h For the first h Second harmonic This is the set of harmonic frequencies that need to be considered when mitigating voltage harmonic distortion. For normalized nodes i and nodes j The normalization of mutual impedance between nodes refers to the calculation of the mutual impedance value between nodes at a certain frequency compared to the maximum mutual impedance value at that frequency. Combined with comprehensive mutual impedance coefficient Obtain the feature vectors of each node :

[0009] in, I This represents the total number of nodes in the distribution network. The feature vectors of nodes connected to active power filters in the distribution network are used as cluster centers. Clustering methods are used to divide the nodes in the distribution network into clusters, and only one node in each cluster is connected to an active power filter.

[0010] As an alternative implementation method, the process of obtaining the impedance and current information of nodes within a partition, performing simplified modeling within the partition, and uploading it to the smart fusion terminal includes: each partition needs to be equipped with a smart IoT meter. The smart IoT meter performs simplified modeling of a partition based on the impedance and current information of the nodes within the partition. During the simplified modeling, the nodes within the partition are divided into two categories: reserved nodes and nodes to be simplified. Reserved nodes are usually pre-set reserved nodes or nodes connected between partitions. Nodes to be simplified are the remaining nodes within the partition.

[0011] As an alternative implementation method, the process of obtaining the total harmonic distortion (THD) rate of voltage at each node in the distribution network, constructing a governance priority sequence, and outputting a voltage harmonic distortion governance enable command to the zone with the most severe voltage harmonic distortion problem includes: collecting the THD of voltage at each node in each zone, and selecting the THD rate of the node with the highest distortion level as an indicator of the severity of voltage harmonic distortion in the zone. According to each partition Establish a governance priority sequence:

[0012] in, It is a priority sequence; For voltage harmonic distortion n Severe partition indexing; For distribution network zones; To return the index sequence that arranges the voltage harmonic distortion index in an ordered manner; Sort in descending order; Priority sequence The indexes in the middle satisfy the following relationship:

[0013] The intelligent fusion terminal indexes as In the partitioned smart IoT meter, the output voltage harmonic distortion mitigation enable command is executed.

[0014] As an alternative implementation, the process of acquiring voltage and current data of the smart meters in the zone with the most severe voltage harmonic distortion problem in the first level, and performing harmonic coupling characteristic modeling for the distributed source loads of the nodes, includes: treating each distributed source load device connected to each node in the distribution network as a nonlinear active device with power greater than a set value, and performing harmonic coupling characteristic modeling, the model being:

[0015] in, for i The current matrices of each distributed source load connected to the node; , These are nodes under the condition of no voltage distortion at the grid connection point. i The emitter current matrix of the connected nonlinear active device, the first h Subharmonic current; For nodes i The harmonic coupling admittance matrix of the connected distributed source load; For the first distributed source-charge launch h Secondary current; For nodes i The b Secondary voltage; To characterize right Influencing admittance elements; The partial least squares method in the complex domain is used to fit and solve the real-time measurement data of the nodes, and the results are obtained. .

[0016] As an alternative implementation method, the process of constructing a distribution network model by combining other simplified models includes: smart IoT meters in the region with the most severe voltage harmonic distortion problem receive simplified models of other regions from the smart fusion terminal, establish a simplified distribution network model from the perspective of this region, and use it as the basis for solving the voltage harmonic distortion mitigation decision in this region. It is assumed that the region with the most severe voltage harmonic distortion problem is the [number missing] region. n Partition, construct its first h Sub-network equations:

[0017] In the formula, , The first n Other partitions besides the reserved node's first h Sub-injection current and voltage matrix; For other partitions h Sub-equivalent current matrix; To characterize the first n The first partition reserved node and other partition reserved nodes h The matrix of secondary admittance relationships; According to the first n The partition retains the first node between other partitions. h After the secondary admittance relation is updated ; For the first n The simplified model of partitions other than the partition itself constitutes the first partition. h Second-node admittance matrix; , The first n Each node in the partition h Secondary voltage and current matrix; For the first nThe nodes of each partition and the reserved nodes of other partitions form the first... h Secondary node impedance matrix.

[0018] As an alternative implementation method, the process of solving the voltage harmonic distortion mitigation decision for a single partition, taking into account the harmonic coupling effects of distributed source loads connected to nodes within the partition, includes: calculating the target values ​​for voltage regulation at each node based on the total voltage harmonic distortion rate and the voltage harmonic content of each order within the partition. : ; ; ; In the formula, To be based on nodes i The proportionality coefficient determined by the degree to which the total harmonic distortion rate of the voltage exceeds the limit; For nodes i Fundamental voltage; For the first h Limits on the harmonic content of each voltage order; For nodes i No. h Harmonic content of each voltage order; As intermediate parameters, to ensure Satisfy the first h Limits on the harmonic content of each harmonic of the secondary voltage; Based on the target value of each voltage adjustment Calculate the amount to be adjusted , Combined with the following formula , The relationship between the compensation current and the active power filter compensation current forms the following relationship between the compensation current and the variable to be adjusted:

[0019] In the formula, impedance matrix No. A submatrix composed of column elements; For the first n The first in the partition s The compensation current of the active power filter connected to the node; Given that all elements are 0, the least squares method is used to solve for the governance decision. Initial value; Introducing adjustment coefficient adjust A decision search for voltage harmonic distortion mitigation considering the influence of harmonic coupling characteristics is conducted, and the adjusted h-th compensation current is determined. The decision variables in voltage harmonic distortion mitigation are:

[0020] Before making a search decision, initialize the search scope:

[0021] In the formula, , These are the lower and upper boundaries of the coefficients during the first search; , These are the minimum and maximum limits of the adjustment coefficient, respectively. Adjustment coefficient in subsequent search The update formula is:

[0022] In the formula: , , The first t Adjustment coefficients, lower and upper boundaries during the next search; According to the t The results of the second search ,calculate ,Will Combined with the harmonic coupling model of distributed source and load, the harmonic power flow of the distribution network considering the coupling characteristics is calculated, and the harmonic voltage situation of each node after the current governance decision is applied to the distribution network is clarified. If the governance target is not met, the governance effect and limiting conditions of node voltage distortion are judged, and the lower and upper boundaries of the adjustment coefficient in the next search are adjusted.

[0023] As a further limitation, the process of adjusting the lower and upper boundaries of the adjustment coefficient in the next search includes: adjusting the search boundaries of each frequency according to the total harmonic distortion rate of the voltage of the nodes in the partition.

[0024]

[0025] In the formula, For the first t In the second search n Maximum total harmonic distortion rate of the partition node voltage; After satisfying the total harmonic distortion (THD) limit, the search boundary for out-of-limit frequencies is adjusted based on the harmonic content of each node within the partition:

[0026] In the formula, For the first t In the second search, the first n Partition node number h The submaximal voltage harmonic content; If, during the search process, the governance decision cannot ensure that all nodes meet the voltage harmonic distortion limit requirements, the search will be terminated based on the search accuracy.

[0027] As an alternative implementation, the method is iteratively performed. The third-level intelligent fusion terminal updates the governance priority sequence and detects whether there are still nodes whose total harmonic distortion rate (THD) exceeds the limit. If there are still nodes whose THD exceeds the limit, governance continues; otherwise, governance ends.

[0028] A distributed voltage harmonic distortion management system suitable for low-voltage distribution networks is a three-tier distributed management architecture, including: The first level includes several smart meters, which are used to respond to the voltage harmonic distortion mitigation enable command. The smart meters corresponding to the partition with the most severe voltage harmonic distortion problem are used to obtain the voltage and current data of the node and perform harmonic coupling characteristic modeling for the distributed source load of the node. The second level includes several smart IoT meters, which are used to acquire the impedance and current information of nodes within the partition, perform simplified modeling within the partition and upload it to the smart fusion terminal. In response to the voltage harmonic distortion mitigation enable command, combined with other partition simplified models, a distribution network model is constructed. Based on the harmonic coupling effect of the distributed source loads connected to the nodes within the partition, the voltage harmonic distortion mitigation decision for a single partition is solved, and the active power filter is controlled to perform voltage harmonic distortion mitigation within the partition. The third level includes several intelligent fusion terminals, which are used to obtain the node relationships and impedance relationships in the distribution network, cluster each node according to the mutual impedance relationship between nodes, obtain the distribution network partitioning results, obtain the total harmonic distortion rate of voltage at each node in the distribution network, construct a governance priority sequence, and output voltage harmonic distortion governance enable commands to the partition with the most serious voltage harmonic distortion problem.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention designs a hierarchical modeling and decision-making mechanism under a three-tier collaborative architecture: smart meters are responsible for modeling the harmonic coupling characteristics of local distributed source loads; smart IoT meters complete simplified modeling and governance decision-making within the zone; and smart fusion terminals coordinate the zone division and priority judgment. This architecture fully utilizes the capabilities of existing smart terminal equipment deployed in low-voltage distribution areas to achieve a reasonable division of labor among different levels for the tasks of "collection-modeling-decision-execution," significantly reducing the need for central computing and high-frequency communication, and meeting the practical constraints of weak hardware conditions and limited data interaction in rural low-voltage distribution networks.

[0030] This invention proposes a distribution network partitioning method based on inter-node mutual impedance relationships. By constructing a comprehensive mutual impedance coefficient and employing a clustering algorithm, electrically tightly coupled nodes are divided into the same governance partition, ensuring that each partition has exactly one active power filter. This method effectively reduces the complexity of overall network modeling while maintaining strong correlations in harmonic interactions within partitions, providing reasonable boundaries for subsequent distributed governance decisions, and avoiding the high dependence of traditional centralized methods on global topology and communication capabilities.

[0031] This invention proposes a harmonic mitigation decision-making method that combines initial value solving with decision search. Taking into account the nonlinear characteristics of distributed source-load harmonic coupling, it first rapidly obtains the initial value of the compensation current using a constant current source assumption. Then, it iteratively searches for the optimal compensation strategy that satisfies the limits of total harmonic distortion (THD) and harmonic content of each order through adjustment coefficients. This method balances solution efficiency and physical accuracy, overcoming the problem of poor mitigation effects caused by traditional linearized models neglecting harmonic interactions between devices, and improving the control accuracy of active power filters in complex harmonic environments.

[0032] This invention addresses the voltage harmonic distortion problem caused by the high proportion of distributed photovoltaic and other power electronic equipment in current low-voltage distribution networks. It proposes a distributed harmonic mitigation method and system suitable for scenarios with weak sensing, weak communication, and weak computing power. It overcomes the dependence of traditional centralized mitigation on high-speed data communication and processing, and instead constructs a three-layer collaborative architecture with intelligent fusion terminals, smart IoT meters, and smart meters as the core. Through partitioning based on mutual impedance, simplified modeling within partitions, identification of harmonic coupling characteristics, and a priority-driven orderly mitigation mechanism, it achieves accurate, efficient, and step-by-step mitigation of harmonic voltage problems under limited measurement and interaction conditions.

[0033] This invention effectively addresses the pain point that existing harmonic mitigation technologies are difficult to implement in rural low-voltage distribution networks, fills the gap in distributed harmonic collaborative control methods for distribution networks with limited hardware conditions, and possesses good engineering feasibility and promotion potential. It can significantly improve the power quality level of low-voltage distribution networks and support the safe consumption of high-penetration distributed energy under the new power system.

[0034] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0035] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0036] Figure 1A flowchart illustrating a distributed voltage harmonic distortion mitigation method suitable for low-voltage distribution networks, as provided in one embodiment.

[0037] Figure 2 A schematic diagram of a three-level distributed governance architecture for voltage harmonic distortion is provided for one embodiment. Detailed Implementation

[0038] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0039] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, 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.

[0040] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0041] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0042] Example 1 like Figure 1 As shown, a distributed method for voltage harmonic distortion mitigation suitable for low-voltage distribution networks includes: S100: Construct a three-level distributed governance architecture for voltage harmonic distortion, with intelligent fusion terminals, smart IoT meters, and smart meters as the cores respectively.

[0043] A three-level distributed governance architecture for voltage harmonic distortion is as follows: Figure 2 As shown.

[0044] The first layer is the node information collection layer. This layer primarily uses smart meters, which possess basic metering, data collection, and simple calculation functions.

[0045] The second layer is the partition modeling and decision-making layer. The decision-making layer primarily uses smart IoT meters, which possess functions such as multi-device IoT, multi-resource control, and edge computing.

[0046] The third layer is the governance priority judgment layer. This layer primarily uses intelligent converged terminals, which possess functions such as data fusion and aggregation, information relay networking, and regional operation and maintenance monitoring.

[0047] S200: The intelligent fusion terminal in the third level obtains the node relationships and impedance relationships in the distribution network, and performs clustering of each node according to the mutual impedance relationship between nodes to obtain the distribution network partitioning results.

[0048] Specifically, in the first level, smart meters model the coupling characteristics of the voltage and current information collected by their respective nodes, performing the modeling task for a single node. In the third level, intelligent fusion terminals acquire the connection and impedance relationships between nodes in the distribution network, cluster the nodes in the distribution network, and form the distribution network partitioning results.

[0049] Based on the impedance information between nodes in the distribution network, node impedance matrices are established for various frequencies. To characterize the impedance relationships between nodes at multiple frequencies, a comprehensive mutual impedance coefficient is proposed. : (1) In the formula: h For the first h Second harmonic This is the set of harmonic frequencies that need to be considered when mitigating voltage harmonic distortion. For normalized nodes i and nodes j The normalization of mutual impedance between nodes refers to the calculation of the mutual impedance value between nodes at a certain frequency compared to the maximum mutual impedance value at that frequency.

[0050] Combined with comprehensive mutual impedance coefficient Obtain the feature vectors of each node : (2) In the formula: I This represents the total number of nodes in the distribution network.

[0051] Using the feature vectors of nodes connected to active power filters in the distribution network as cluster centers, the K-Means method is employed to cluster the nodes in the distribution network. This method is classic and widely used in distribution network modeling, so it will not be elaborated further. This ensures that the electrical connections between nodes in each cluster are more tightly linked, and that only one node in each cluster is connected to an active power filter. The nodes in a cluster constitute a partition, and each partition has exactly one active power filter.

[0052] S300: The smart IoT meter in the second level acquires the impedance and current information of nodes within the partition, performs simplified modeling within the partition, and uploads it to the smart fusion terminal.

[0053] Each zone requires the installation of a smart IoT meter. The smart IoT meter performs a simplified modeling of a zone based on the node impedance and current information. During simplified modeling, nodes within the zone are divided into two categories: reserved nodes and nodes to be simplified. Reserved nodes are typically manually selected nodes or nodes connecting different zones. Nodes to be simplified are the remaining nodes within the zone. This embodiment can employ the Kron simplification method, which is widely used in distribution network modeling and will not be elaborated upon further.

[0054] S400: The intelligent fusion terminal in the third level obtains the total harmonic distortion rate of voltage at each node in the distribution network, constructs a governance priority sequence, and outputs voltage harmonic distortion governance enable commands to the zone with the most severe voltage harmonic distortion problem.

[0055] The total harmonic distortion (THD) of voltage at each node in each partition is collected, and the THD rate of the node with the highest distortion level is selected as the index of the severity of voltage harmonic distortion in the partition. According to each partition Establish a governance priority sequence: (3) In the formula: It is a priority sequence; For voltage harmonic distortion n Severe partition indexing; For distribution network zones; To return the index sequence that arranges the voltage harmonic distortion index in an ordered manner; Arranged in descending order; priority sequence The indexes in the middle satisfy the following relationship: (4) The intelligent fusion terminal indexes as In the partitioned smart IoT meter, the output voltage harmonic distortion mitigation enable command is executed.

[0056] S500: The smart meter in the first-level partition with the most severe voltage harmonic distortion problem acquires the voltage and current data of the node and performs harmonic coupling characteristic modeling for the distributed source and load of the node.

[0057] In a power distribution network, each node typically connects to various types of distributed source-load devices, including linear devices, nonlinear active devices, and nonlinear passive devices. In the modeling process, this set of devices can be considered as a single, high-power nonlinear active device. A method for modeling the harmonic coupling characteristics of this distributed source-load device set is proposed. The specific form of the model is as follows: (5) In the formula: for iThe current matrices of each distributed source load connected to the node; , These are nodes under the condition of no voltage distortion at the grid connection point. i The emitter current matrix of the connected nonlinear active device, the first h Subharmonic current; For nodes i The harmonic coupling admittance matrix of the connected distributed source load; For the first distributed source-charge launch h Secondary current; For nodes i The b Secondary voltage; To characterize right The admittance element that influences the outcome.

[0058] In the distribution network, the vast majority of nonlinear active devices are distributed photovoltaics, therefore in equation (5) This can be obtained during the factory testing of distributed photovoltaic systems. Additionally, by using the partial least squares method in the complex domain to fit and solve the real-time node measurement data, we can obtain the solution in equation (5). This fitting method is very classic, so it will not be elaborated further.

[0059] S600: Upon receiving the voltage harmonic distortion mitigation enable command, the smart IoT meters in the partition, combined with simplified models of other partitions, construct a distribution network model. Taking into account the harmonic coupling effects of distributed source loads connected to nodes within the partition, it solves the voltage harmonic distortion mitigation decision for a single partition. Then, it controls the active power filter to perform voltage harmonic distortion mitigation within the partition.

[0060] S601: The smart IoT meter in the zone with the most severe voltage harmonic distortion problem receives simplified models from other zones from the smart fusion terminal, establishes a simplified distribution network model from the perspective of this zone, and serves as the basis for solving voltage harmonic distortion mitigation decisions in this zone. Assume that the zone with the most severe voltage harmonic distortion problem is currently zone S601. n Partition, construct its first h Secondary network equations.

[0061] (6) In the formula: , The first n Other partitions besides the reserved node's first h Sub-injection current and voltage matrix; For other partitions h Sub-equivalent current matrix; To characterize the first n The first partition reserved node and other partition reserved nodes hThe matrix of secondary admittance relationships; According to the first n The partition retains the first node between other partitions. h After the secondary admittance relation is updated ; For the first n The simplified model of partitions other than the partition itself constitutes the first partition. h Second-node admittance matrix; , The first n Each node in the partition h Secondary voltage and current matrix; For the first n The nodes of each partition and the reserved nodes of other partitions form the first... h Secondary node impedance matrix.

[0062] S602: To solve voltage harmonic distortion mitigation decisions considering the influence of harmonic coupling characteristics, a decision-solving method combining initial value solving and decision search is proposed. Initial value solving involves temporarily treating harmonic sources in the distribution network as constant current sources and using a non-iterative solution method to initially solve for mitigation decisions. Decision search involves substituting the initial values ​​into the network equations considering the influence of harmonic coupling characteristics and adjusting the mitigation decisions based on the relationship between mitigation performance and limit boundaries.

[0063] Based on the total harmonic distortion rate and harmonic content of voltage at each node within the partition, calculate the target values ​​for voltage regulation at each node. .

[0064] (7) (8) (9) In the formula: To be based on nodes i The proportionality coefficient determined by the degree to which the total harmonic distortion rate of the voltage exceeds the limit; For nodes i Fundamental voltage; For the first h Limits on the harmonic content of each voltage order; For nodes i No. h Harmonic content of each voltage order; As intermediate parameters, to ensure Satisfy the first h Limits on the content of each harmonic of the secondary voltage.

[0065] Based on the target value of each voltage adjustment Calculate the amount to be adjusted , Combined with equation (10) , The relationship between the compensation current and the active power filter compensation current forms the following relationship between the compensation current and the variable to be adjusted: (10) In the formula: impedance matrix No. A submatrix composed of column elements; For the first n The first in the partition s The compensation current of the active power filter connected to the node; All elements in the middle are 0 because the active power filter primarily targets the harmonic voltages of nodes within its own zone, without attempting to mitigate the harmonics of nodes in other zones. The least squares method is used to solve for the mitigation decision. The initial value of .

[0066] The essence of governance decision search is to consider the impact of harmonic coupling characteristics in the distribution network and find a more suitable compensation current near the initial value so that the voltage at each node after governance meets the limits of total harmonic distortion and harmonic content of each voltage. An adjustment coefficient is introduced. adjust A decision-making search for voltage harmonic distortion mitigation considering the influence of harmonic coupling characteristics is conducted. The adjusted h-th compensation current... , which are the decision variables in voltage harmonic distortion control, as shown below.

[0067] (11) Before making a search decision, the search scope is initialized.

[0068] (12) In the formula: , These are the lower and upper boundaries of the coefficients during the first search; , These represent the minimum and maximum limits of the adjustment coefficient, respectively.

[0069] Adjustment coefficient in subsequent search The update formula is: (13) In the formula: , , The first t Adjustment coefficients, lower and upper boundaries during the next search.

[0070] According to the t The results of the second search It can be calculated .Will Substituting the distributed source-load harmonic coupling model shown in equation (5) into equation (6), the harmonic power flow of the distribution network considering coupling characteristics can be calculated. This clarifies the harmonic voltage situation of each node after the current governance decision is applied to the distribution network. If the governance objective is not met, it is necessary to judge the governance effect and limiting conditions of node voltage distortion and adjust the lower and upper boundaries of the adjustment coefficient in the next search.

[0071] The search boundaries for each frequency are adjusted based on the total harmonic distortion of the voltage at the nodes within the partition.

[0072] (14) In the formula: For the first t In the second search n Maximum total harmonic distortion of the voltage at partition nodes.

[0073] After satisfying the total harmonic distortion rate limit, the search boundary for the frequency exceeding the limit is adjusted according to the voltage harmonic content of each node in the partition.

[0074] (1) In the formula: For the first t In the second search, the first n Partition node number h The maximum voltage harmonic content.

[0075] If, during the search process, the governance decision cannot ensure that all nodes meet the voltage harmonic distortion limit requirements, the search must be terminated based on the search accuracy.

[0076] (16) In the formula: For tolerance, it is usually set to a small positive number.

[0077] S603: The n The first in the partition s The compensation current of the active power filter connected to the node executes the command decision. To address voltage harmonic distortion within the assigned zone.

[0078] S700: The third-level intelligent fusion terminal detects whether there are still nodes whose total harmonic distortion rate exceeds the limit, and determines whether to continue treatment or end treatment.

[0079] The intelligent fusion terminal updates the governance priority sequence of equation (3) and determines the citation. If the total harmonic distortion rate of the node voltage in the partition still exceeds the limit, repeat S400, S500 and S600; if it does not exceed the limit, end the treatment.

[0080] Example 2 A distributed voltage harmonic distortion management system suitable for low-voltage distribution networks is a three-tier distributed management architecture, including: The first level includes several smart meters, which are used to obtain the node relationships and impedance relationships in the distribution network. Based on the mutual impedance relationship between nodes, each node is clustered and divided to obtain the distribution network partitioning results. In response to the voltage harmonic distortion mitigation enable command, the smart meter corresponding to the partition with the most severe voltage harmonic distortion problem is used to obtain the voltage and current data of the node and perform harmonic coupling characteristic modeling for the distributed source load of the node. The second level includes several smart IoT meters, which are used to acquire the impedance and current information of nodes within the partition, perform simplified modeling within the partition and upload it to the smart fusion terminal. In response to the voltage harmonic distortion mitigation enable command, combined with other partition simplified models, a distribution network model is constructed. Based on the harmonic coupling effect of the distributed source loads connected to the nodes within the partition, the voltage harmonic distortion mitigation decision for a single partition is solved, and the active power filter is controlled to perform voltage harmonic distortion mitigation within the partition. The third level includes several intelligent fusion terminals, which are used to obtain the total harmonic distortion rate of voltage at each node in the distribution network, construct a governance priority sequence, and output voltage harmonic distortion governance enable commands to the partition with the most severe voltage harmonic distortion problem.

[0081] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of one or more computer-usable storage media (including, but not limited to, disk storage, etc.) containing computer-usable program code. CD - ROM It takes the form of a computer program product implemented on (such as optical memory, etc.).

[0082] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0083] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0084] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A distributed method for voltage harmonic distortion mitigation in low-voltage distribution networks, characterized in that, Includes the following steps: A three-tier distributed governance architecture for voltage harmonic distortion is constructed. The first tier includes several smart meters, the second tier includes several smart IoT meters, and the third tier includes several smart converged terminals. Obtain the node relationships and impedance relationships in the distribution network, and perform clustering of each node according to the mutual impedance relationship between nodes to obtain the distribution network partitioning results; Obtain the node impedance and current information within the partition, perform simplified modeling within the partition, and upload it to the intelligent fusion terminal; Obtain the total harmonic distortion rate of voltage at each node in the distribution network, construct a governance priority sequence, and output a voltage harmonic distortion governance enable command to the zone with the most severe voltage harmonic distortion problem. In response to the voltage harmonic distortion mitigation enable command, the smart meters in the first-level partition with the most severe voltage harmonic distortion problem acquire the voltage and current data of the node and perform harmonic coupling characteristic modeling for the distributed source and load of the node. In response to the voltage harmonic distortion mitigation enable command, the second-level smart IoT meter, combined with other simplified partition models, constructs a distribution network model. Taking into account the harmonic coupling effects of distributed source loads connected to nodes within the partition, it solves the voltage harmonic distortion mitigation decision for a single partition and controls the active power filter to perform voltage harmonic distortion mitigation within the partition.

2. The distributed voltage harmonic distortion mitigation method for low-voltage distribution networks as described in claim 1, characterized in that, The process of obtaining the node relationships and impedance relationships in a distribution network, and clustering the nodes based on the mutual impedance relationships to obtain the distribution network partitioning results includes: establishing node impedance matrices at various frequencies based on the impedance information between each node in the distribution network; and proposing a comprehensive mutual impedance coefficient to characterize the impedance relationships between nodes at multiple frequencies. : In the formula, h For the first h Second harmonic This is the set of harmonic frequencies that need to be considered when mitigating voltage harmonic distortion. For normalized nodes i and nodes j The normalization of mutual impedance between nodes refers to the calculation of the mutual impedance value between nodes at a certain frequency compared to the maximum mutual impedance value at that frequency. Combined with comprehensive mutual impedance coefficient Obtain the feature vectors of each node : in, I This represents the total number of nodes in the distribution network. The feature vectors of nodes connected to active power filters in the distribution network are used as cluster centers. Clustering methods are used to divide the nodes in the distribution network into clusters, and only one node in each cluster is connected to an active power filter.

3. The distributed voltage harmonic distortion mitigation method for low-voltage distribution networks as described in claim 1, characterized in that, The process of acquiring the impedance and current information of nodes within a partition, performing simplified modeling within the partition, and uploading it to the smart fusion terminal includes: each partition needs to be equipped with a smart IoT meter. The smart IoT meter performs simplified modeling of a partition based on the impedance and current information of the nodes within the partition. During the simplified modeling, the nodes within the partition are divided into two categories: reserved nodes and nodes to be simplified. Reserved nodes are usually pre-set reserved nodes or nodes connected between partitions. Nodes to be simplified are the remaining nodes within the partition.

4. The distributed voltage harmonic distortion mitigation method for low-voltage distribution networks as described in claim 1, characterized in that, The process of obtaining the total harmonic distortion (THD) rate of voltage at each node in the distribution network, constructing a priority sequence for mitigation, and outputting a voltage harmonic distortion mitigation enable command to the zone with the most severe voltage harmonic distortion problem includes: collecting the THD of voltage at each node in each zone, and selecting the THD rate of the node with the highest distortion level as the severity index of voltage harmonic distortion in the zone. According to each partition Establish a governance priority sequence: in, It is a priority sequence; For voltage harmonic distortion n Severe partition indexing; For distribution network zones; To return the index sequence that arranges the voltage harmonic distortion index in an ordered manner; Sort in descending order; Priority sequence The indexes in the middle satisfy the following relationship: The intelligent fusion terminal indexes as In the partitioned smart IoT meters, the output voltage harmonic distortion mitigation enable command is provided.

5. The distributed voltage harmonic distortion mitigation method for low-voltage distribution networks as described in claim 1, characterized in that, In the first level, the smart meters in the zone with the most severe voltage harmonic distortion problem acquire voltage and current data of their respective nodes. The process of modeling the harmonic coupling characteristics of the distributed source-loads at these nodes includes: treating each distributed source-load device connected to each node in the distribution network as a nonlinear active device with power exceeding a set value, and modeling its harmonic coupling characteristics. The model is as follows: in, for i The current matrices of each distributed source load connected to the node; , These are nodes under the condition of no voltage distortion at the grid connection point. i The emitter current matrix of the connected nonlinear active device, the first h Subharmonic current; For nodes i The harmonic coupling admittance matrix of the connected distributed source load; For the first distributed source-charge launch h Secondary current; For nodes i The b Secondary voltage; To characterize right Influencing admittance elements; The partial least squares method in the complex domain is used to fit and solve the real-time measurement data of the nodes, and the results are obtained. .

6. The distributed voltage harmonic distortion mitigation method for low-voltage distribution networks as described in claim 1, characterized in that, The process of constructing a distribution network model by combining simplified models of other zones includes: smart IoT meters in the zone with the most severe voltage harmonic distortion problem; receiving simplified models of other zones from the smart fusion terminal; establishing a simplified distribution network model from the perspective of this zone; and using this model as the basis for solving voltage harmonic distortion mitigation decisions in this zone. It is assumed that the zone with the most severe voltage harmonic distortion problem is the [number missing] zone. n Partition, construct its first h Sub-network equations: In the formula, , The first n Other partitions besides the reserved node's first h Sub-injection current and voltage matrix; For other partitions h Sub-equivalent current matrix; To characterize the first n The first partition reserved node and other partition reserved nodes h The matrix of secondary admittance relationships; According to the first n The partition retains the first node between other partitions. h After the secondary admittance relation is updated ; For the first n The simplified model of partitions other than the partition constitutes the first h Second-node admittance matrix; , The first n Each node in the partition h Secondary voltage and current matrix; For the first n The nodes of each partition and the reserved nodes of other partitions form the first... h Secondary node impedance matrix.

7. The distributed voltage harmonic distortion mitigation method for low-voltage distribution networks as described in claim 1, characterized in that, Taking into account the harmonic coupling effects of distributed source loads connected to nodes within a partition, the process of solving the voltage harmonic distortion mitigation decision for a single partition includes: calculating the target voltage regulation values ​​for each node based on the total voltage harmonic distortion rate and the voltage harmonic content rate of each node within the partition. : ； ； ； In the formula, To be based on nodes i The proportionality coefficient determined by the degree to which the total harmonic distortion rate of the voltage exceeds the limit; For nodes i Fundamental voltage; For the first h Limits on the harmonic content of each voltage order; For nodes i No. h Harmonic content of each voltage order; As intermediate parameters, to ensure Satisfy the first h Limits on the harmonic content of each harmonic of the secondary voltage; Based on the target value of each voltage adjustment Calculate the amount to be adjusted , Combined with the following formula , The relationship between the compensation current and the active power filter compensation current forms the following relationship between the compensation current and the variable to be adjusted: In the formula, impedance matrix No. A submatrix composed of column elements; For the first n The first in the partition s The compensation current of the active power filter connected to the node; Given that all elements are 0, the least squares method is used to solve for the governance decision. Initial value; Introducing adjustment coefficient adjust A decision search for voltage harmonic distortion mitigation considering the influence of harmonic coupling characteristics is conducted, and the adjusted h-th compensation current is determined. The decision variables in voltage harmonic distortion mitigation are: Before making a search decision, initialize the search scope: In the formula, , These are the lower and upper boundaries of the coefficients during the first search; , These are the minimum and maximum limits of the adjustment coefficient, respectively. Adjustment coefficient in subsequent search The update formula is: In the formula: , , The first t Adjustment coefficients, lower and upper boundaries during the next search; According to the t The results of the second search ,calculate ,Will Combined with the harmonic coupling model of distributed source and load, the harmonic power flow of the distribution network considering the coupling characteristics is calculated, and the harmonic voltage situation of each node after the current governance decision is applied to the distribution network is clarified. If the governance target is not met, the governance effect and limiting conditions of node voltage distortion are judged, and the lower and upper boundaries of the adjustment coefficient in the next search are adjusted.

8. The distributed voltage harmonic distortion mitigation method for low-voltage distribution networks as described in claim 7, characterized in that, The process of adjusting the lower and upper boundaries of the adjustment coefficient in the next search includes: adjusting the search boundaries of each frequency according to the total harmonic distortion of the voltage of the nodes in the partition; In the formula, For the first t In the second search n Maximum total harmonic distortion rate of the partition node voltage; After satisfying the total harmonic distortion (THD) limit, the search boundary for out-of-limit frequencies is adjusted based on the harmonic content of each node within the partition: In the formula, For the first t In the second search, the first n Partition node number h The submaximal voltage harmonic content; If, during the search process, the governance decision cannot ensure that all nodes meet the voltage harmonic distortion limit requirements, the search will be terminated based on the search accuracy.

9. A distributed voltage harmonic distortion mitigation method suitable for low-voltage distribution networks as described in claim 1, characterized in that, The method is iterative. The third-level intelligent fusion terminal updates the governance priority sequence and detects whether there are still nodes whose total harmonic distortion rate (THD) exceeds the limit. If there are still nodes whose THD exceeds the limit, governance continues; otherwise, governance ends.

10. A distributed voltage harmonic distortion control system suitable for low-voltage distribution networks, characterized in that, It is a three-tier distributed governance architecture, including: The first level includes several smart meters, which are used to respond to the voltage harmonic distortion mitigation enable command. The smart meters corresponding to the partition with the most severe voltage harmonic distortion problem are used to obtain the voltage and current data of the node and perform harmonic coupling characteristic modeling for the distributed source load of the node. The second level includes several smart IoT meters, which are used to acquire the impedance and current information of nodes within the partition, perform simplified modeling within the partition and upload it to the smart fusion terminal. In response to the voltage harmonic distortion mitigation enable command, combined with other partition simplified models, a distribution network model is constructed. Based on the harmonic coupling effect of the distributed source loads connected to the nodes within the partition, the voltage harmonic distortion mitigation decision for a single partition is solved, and the active power filter is controlled to perform voltage harmonic distortion mitigation within the partition. The third level includes several intelligent fusion terminals, which are used to obtain the node relationships and impedance relationships in the distribution network, cluster each node according to the mutual impedance relationship between nodes, obtain the distribution network partitioning results, obtain the total harmonic distortion rate of voltage at each node in the distribution network, construct a governance priority sequence, and output voltage harmonic distortion governance enable commands to the partition with the most serious voltage harmonic distortion problem.

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