Method and device for determining harmonic source position of power distribution network, electronic equipment and medium

Abstract

The invention discloses a method and device for determining the position of a harmonic source of a power distribution network, electronic equipment and a medium, and the method comprises the steps: obtaining the harmonic current information of a plurality of initial nodes in a power distribution system, determining a target section according to the harmonic current information, the target section comprises a plurality of target links, the position information of the target harmonic source is determined from the plurality of target links according to a target measurement matrix set, and the target measurement matrix set comprises a first-dimensional measurement matrix, a second-dimensional measurement matrix and a state variable matrix. According to the invention, the technical problem of low positioning accuracy of the harmonic source in the power distribution system in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the field of automation technology, and in particular to a method, device, electronic equipment and medium for determining the position of a harmonic source in a distribution network. Background Art

[0002] In modern society, with the widespread application of power electronic equipment, higher requirements are placed on the control of harmonic pollution in power systems. In the process of connecting power electronic equipment to the power system, nonlinear loads distort the voltage and current waveforms of the power grid and generate a large number of harmonics. Excessive harmonic content not only causes electromagnetic interference to the power grid, but also affects the normal operation of power electronic equipment, and even causes overheating, aging, and shortened life of power electronic equipment, affecting the stable operation of the power grid and the economic operation of the system. In severe cases, it causes damage to equipment and power line accidents. Therefore, the issue of harmonic control in distribution networks has attracted much attention in recent years, and mastering the harmonic distribution of the power grid and accurately locating the harmonic source are its premise and foundation.

[0003] Harmonic state estimation based on the principle of complete observability of the system is the most commonly used method for locating harmonic sources at this stage. That is, based on the harmonic voltage and current data of a limited number of measurement points, combined with the topology and parameters of the power grid, a linear measurement model is established through network analysis to estimate the harmonic state of the power grid. However, it is difficult to carry out harmonic state estimation of distribution networks based on complete observability conditions. In essence, it is a state estimation problem for complex systems with low observability. The prominent difficulty brought about by low observability is that the established measurement equation is underdetermined, the model has a non-unique solution, and it is difficult to locate harmonic sources.

[0004] At present, there are usually two ways to deal with underdetermined equations. The first is to transform the underdetermined equations into exactly or overdetermined equations for solution. Commonly used methods include reducing the state quantity to be estimated, converting the unobservable area into an equivalent observable area, etc. However, the harmonic state estimation error of this method is high, and as the number of nodes increases, the calculation dimension and complexity increase exponentially.

[0005] The second method is to use singular value decomposition, independent component analysis, linear programming and other methods to directly solve the underdetermined equation from a mathematical point of view. However, this method may lead to incorrect solutions due to the infinite number of solutions of the underdetermined equation, and it is easily affected by factors such as the position of the measuring point, measurement noise and asynchronous measurement of the measuring point, resulting in positioning failure.

[0006] Currently, no corresponding solution has been proposed for the above problems. Summary of the invention

[0007] Embodiments of the present invention provide a method, device, electronic device and medium for determining the position of a harmonic source in a power distribution network, so as to at least solve the technical problem of low accuracy in locating the position of a harmonic source in a power distribution system in the prior art.

[0008] According to one embodiment of the present invention, there is provided a method for determining the location of a harmonic source in a distribution network, comprising: acquiring harmonic current information of a plurality of initial nodes in the distribution system, wherein the plurality of initial nodes are nodes equipped with measurement devices; determining a target section according to the harmonic current information, wherein the target section comprises a plurality of target links; determining the location information of a target harmonic source from the plurality of target links according to a target measurement matrix set, wherein the target measurement matrix set comprises a first-dimensional measurement matrix, a second-dimensional measurement matrix and a state variable matrix.

[0009] Optionally, the method for determining the location of a harmonic source in a distribution network further includes: acquiring a plurality of circuit nodes of the distribution system; and determining a plurality of initial nodes from the plurality of circuit nodes, wherein the plurality of initial nodes include at least boundary nodes, branch nodes, and link nodes.

[0010] Optionally, the method for determining the location of harmonic sources in the distribution network also includes: acquiring multiple initial sections of the distribution system based on multiple initial nodes; determining multiple balancing nodes from the multiple initial sections; and measuring current information of the multiple balancing nodes to obtain harmonic current information.

[0011] Optionally, the method for determining the location of a harmonic source in a distribution network further includes: classifying a plurality of circuit nodes based on an initial node to obtain a plurality of node sets; and performing a clustering topology operation on the plurality of node sets to obtain a plurality of initial sections.

[0012] Optionally, the method for determining the location of harmonic sources in a distribution network also includes: obtaining a target measurement matrix set based on harmonic current information; generating an initial harmonic state estimation model based on the target measurement matrix set; determining a target node based on the initial harmonic state estimation model; and determining a target section based on the target node.

[0013] Optionally, the method for determining the location of a harmonic source in a distribution network also includes: determining a first initial node and a second initial node of a target section; obtaining first harmonic current information of the first initial node and second harmonic current information of the second initial node; and determining the location information of a target harmonic source from multiple target links based on the first harmonic current information, the second harmonic current information and a target measurement matrix set.

[0014] Optionally, the method for determining the location of a harmonic source in a distribution network also includes: establishing a state relationship matrix based on first harmonic current information and second harmonic current information; generating a target harmonic state estimation model based on the state relationship matrix and a target measurement matrix set; and determining the location information of the target harmonic source based on the target harmonic state estimation model.

[0015] According to one embodiment of the present invention, there is also provided a device for determining the position of a harmonic source in a distribution network, comprising: a first acquisition module, used to acquire harmonic current information of multiple initial nodes in the distribution system, wherein the multiple initial nodes are nodes equipped with measurement devices; a first determination module, used to determine a target section according to the harmonic current information, wherein the target section includes multiple target links; a second determination module, used to determine the position information of a target harmonic source from multiple target links according to a target measurement matrix set, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix and a state variable matrix.

[0016] Optionally, the device for determining the location of a harmonic source in a distribution network also includes: a second acquisition module, used to acquire multiple circuit nodes of the distribution system; and a third determination module, used to determine multiple initial nodes from the multiple circuit nodes, wherein the multiple initial nodes include at least boundary nodes, branch nodes, and link nodes.

[0017] Optionally, the first acquisition module includes: a first acquisition unit, used to acquire multiple initial sections of the distribution system based on multiple initial nodes; a first determination unit, used to determine multiple balancing nodes from the multiple initial sections; and a measurement unit, used to measure current information of multiple balancing nodes to obtain harmonic current information.

[0018] Optionally, the first acquisition unit includes: a classification subunit, used to classify multiple circuit nodes based on the initial node to obtain multiple node sets; and an execution subunit, used to perform a clustering topology operation on the multiple node sets to obtain multiple initial segments.

[0019] Optionally, the first determination module includes: a second acquisition unit, used to acquire a target measurement matrix set based on harmonic current information; a generation unit, used to generate an initial harmonic state estimation model based on the target measurement matrix set; a second determination unit, used to determine the target node based on the initial harmonic state estimation model; and a third determination unit, used to determine the target section based on the target node.

[0020] Optionally, the second determination module includes: a fourth determination unit, used to determine the first initial node and the second initial node of the target segment; a third acquisition unit, used to acquire the first harmonic current information of the first initial node and the second harmonic current information of the second initial node; and a fifth determination unit, used to determine the location information of the target harmonic source from multiple target links based on the first harmonic current information, the second harmonic current information and the target measurement matrix set.

[0021] Optionally, the fifth determination unit includes: an establishment subunit, used to establish a state relationship matrix based on the first harmonic current information and the second harmonic current information; a generation subunit, used to generate a target harmonic state estimation model based on the state relationship matrix and the target measurement matrix set; and a determination subunit, used to determine the location information of the target harmonic source based on the target harmonic state estimation model.

[0022] According to one embodiment of the present invention, there is further provided an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute any of the above methods for determining the location of a harmonic source in a distribution network.

[0023] According to one embodiment of the present invention, a computer-readable storage medium is provided, in which a computer program is stored, wherein the computer program is configured to execute any of the above methods for determining the location of a harmonic source in a distribution network when run.

[0024] In an embodiment of the present invention, the harmonic current information of multiple initial nodes in the distribution system is obtained, wherein the multiple initial nodes are nodes equipped with measurement devices, thereby achieving the purpose of determining the target section according to the harmonic current information, wherein the target section includes multiple target links, and achieving the technical effect of determining the position information of the target harmonic source from the multiple target links according to the target measurement matrix set, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix and a state variable matrix, thereby solving the technical problem of low accuracy in positioning the position of the harmonic source in the distribution system in the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0026] Figure 1 is a flow chart of a method for determining the location of a harmonic source in a distribution network according to one embodiment of the present invention;

[0027] Figure 2 is a schematic diagram of three types of nodes on a radial feeder according to one embodiment of the present invention;

[0028] Figure 3 is a schematic diagram of a hierarchical estimation algorithm system partitioning method according to one embodiment of the present invention;

[0029] Figure 4 It is a structural block diagram of a device for determining the location of harmonic sources in a distribution network according to one embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0031] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0032] According to an embodiment of the present invention, an embodiment of a method for determining the location of a harmonic source in a distribution network is provided. It should be noted that the steps shown in the flowchart of the accompanying drawings can be executed in a computer system comprising at least one set of computer executable instructions, and although a logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in an order different from that shown here.

[0033] The method embodiment may also be performed in an electronic device, a similar control device or an electronic device including a memory and a processor. Taking an electronic device as an example, the electronic device may include one or more processors and a memory for storing data. Optionally, the electronic device may also include a communication device and a display device for communication functions. It will be understood by those skilled in the art that the above structural description is only illustrative and does not limit the structure of the above electronic device. For example, the electronic device may also include more or fewer components than the above structural description, or have a configuration different from the above structural description.

[0034] The processor may include one or more processing units. For example, the processor may include a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processing (DSP) chip, a microcontroller unit (MCU), a field-programmable gate array (FPGA), a neural-network processing unit (NPU), a tensor processing unit (TPU), an artificial intelligence (AI) type processor, and the like. Among them, different processing units may be independent components or integrated into one or more processors. In some instances, the electronic device may also include one or more processors.

[0035] The memory can be used to store computer programs, such as storing a computer program corresponding to the method for determining the location of the harmonic source of the power distribution network in the embodiment of the present invention. The processor implements the above-mentioned method for determining the location of the harmonic source by running the computer program stored in the memory. The memory may include a high-speed random access memory, and may also include a non-volatile memory, such as one or more magnetic storage devices, flash memory, or other non-volatile solid-state memory. In some examples, the memory may further include a memory remotely arranged relative to the processor, and these remote memories can be connected to the electronic device via a grid. Examples of the above-mentioned grid include, but are not limited to, the Internet, an intranet, a local area network, a mobile communication network, and combinations thereof.

[0036] The communication device is used to receive or send data via a grid. The specific examples of the above-mentioned grid may include a wireless grid provided by a communication provider of the mobile terminal. In one example, the communication device includes a grid adapter (network interface controller, NIC), which can be connected to other grid devices through a base station so as to communicate with the Internet. In one example, the communication device can be a radio frequency (RF) module, which is used to communicate with the Internet wirelessly. In some embodiments of the present solution, the communication device is used to connect to mobile devices such as mobile phones and tablets, and instructions can be sent to the vehicle-mounted terminal through the mobile device.

[0037] The display device may be a touch screen type liquid crystal display (LCD) and a touch display (also referred to as a "touch screen" or "touch display screen"). The liquid crystal display may enable a user to interact with a user interface of the vehicle-mounted terminal. In some embodiments, the vehicle-mounted terminal has a graphical user interface (GUI), and a user may interact with the GUI by finger contact and / or gestures on a touch-sensitive surface. The human-computer interaction function here may include a vehicle gear shifting function, and executable instructions for executing the human-computer interaction function are configured / stored in a computer program product or a readable storage medium executable by one or more processors.

[0038] Figure 1 is a flow chart of a method for determining the location of a harmonic source in a distribution network according to one embodiment of the present invention. Figure 1 As shown, the method comprises the following steps:

[0039] Step S102 , obtaining harmonic current information of a plurality of initial nodes in the power distribution system, wherein the plurality of initial nodes are nodes equipped with measurement devices.

[0040] Optionally, the execution subject of this embodiment is a harmonic source position determination system. It should be noted that other electronic devices and processors can also serve as execution subjects, and no further limitations are given here.

[0041] Specifically, in the power distribution system, the initial node refers to the node where the measurement device is installed. The measurement device can directly provide these nodes with real-time voltage and current phasor data, including voltage and current amplitude and phase information, which is the basis for system state estimation and monitoring.

[0042] Among them, the measuring device can be exemplified as a phasor measurement unit (PMU). PMU is a device used to synchronously measure voltage and current phasors in the power system. PMU can capture the amplitude and phase information of voltage and current at each node in the power system in real time, and ensure that these measurements are performed under the same time reference through the global positioning system or other synchronization signals, thereby realizing wide-area synchronous phasor measurement.

[0043] Exemplarily, obtaining harmonic current information of multiple initial nodes in a power distribution system through a PMU includes the following steps: synchronous sampling, the PMU uses a global positioning system to achieve high-speed and accurate sampling of the current waveform of each initial node, ensuring that all measured data are acquired under the same time reference; harmonic analysis, the original current data collected by the PMU needs to be analyzed through Fourier transform (usually fast Fourier transform) to convert the time domain signal into a frequency domain signal, thereby extracting the amplitude and phase information of each harmonic current. For harmonic analysis in the power distribution system, it is necessary to pay attention to integer multiples of the fundamental frequency, that is, 2nd, 3rd, 5th, 7th and other harmonics; data packaging and transmission: the analyzed harmonic current information is packaged by the PMU into a standard data format, such as CIM (Common Information Model), SVG (Scalable Vector Graphics) or a special data transmission protocol of the PMU, and then transmitted to the central control center or data analysis platform in real time through the communication network.

[0044] Step S104: determining a target section according to the harmonic current information, wherein the target section includes a plurality of target links.

[0045] Specifically, the power distribution system is divided into a plurality of sections defined by different types of nodes (such as head-end nodes, terminal nodes and branch nodes) as initial sections, and each initial section includes a plurality of links.

[0046] Based on the initial segment division, the current measurement data of the downstream endpoints (i.e., the balancing nodes) of each segment represent the branch current of the segment. Since the flow direction of the harmonic current is always from the injection node to the balancing node, the direction toward the balancing node is defined as the downstream of the harmonic transfer path, and the direction away from the balancing node is defined as the upstream. If there is a harmonic source in the segment, the harmonic current will only flow through the downstream measurement point, so only the measurement data of the downstream endpoint contains the harmonic current information in the segment, so the downstream measurement result is selected.

[0047] Based on the current measurement data of the downstream endpoints of each section obtained above, the first-level harmonic state estimation model is constructed, which is a mixed integer quadratic programming problem model. By solving the first-level harmonic state estimation model, the flow path of the harmonic current is identified, so as to determine the section where the harmonic source may be located, that is, the target section. Each target section consists of multiple target links, which are the paths through which the harmonic current flows.

[0048] Step S106, determining the location information of the target harmonic source from the multiple target links according to the target measurement matrix set, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix, and a state variable matrix.

[0049] Specifically, the target measurement matrix set consists of a first-dimensional measurement matrix, a second-dimensional measurement matrix, and a state variable matrix. These matrices reflect the relationship between the measurement data and the system state, and are the basis for harmonic state estimation. Among them, the first-dimensional measurement matrix is ​​used to distinguish which nodes or branches are actually measured for current and voltage, and the second-dimensional measurement matrix is ​​used to describe the relationship between the harmonic voltage and current of nodes and branches that are not equipped with measurement devices. Even if there is no direct measurement at these locations, the state information can be indirectly obtained through the association with the measured nodes and branches.

[0050] Specifically, after determining the target section where the harmonic source is located, the target link of the section where the harmonic source is located is determined according to the determined harmonic current path, and then the second-layer harmonic state estimation model is constructed, which is also a mixed integer quadratic programming problem model. By solving the above-constructed mixed integer quadratic programming problem, the specific location information of the harmonic source in the target section can be further determined.

[0051] From the above steps S102 to S106, it can be known that in the present invention, the harmonic current information of multiple initial nodes in the distribution system is obtained, wherein the multiple initial nodes are nodes equipped with measurement devices, so as to achieve the purpose of determining the target section according to the harmonic current information, wherein the target section includes multiple target links, and the technical effect of determining the position information of the target harmonic source from the multiple target links according to the target measurement matrix set is achieved, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix and a state variable matrix, thereby solving the technical problem of low accuracy in positioning the harmonic source in the distribution system in the prior art.

[0052] The above method of this embodiment is further described in detail below.

[0053] As an optional implementation, the method for determining the location of a harmonic source in a distribution network also includes: acquiring multiple circuit nodes of the distribution system; determining multiple initial nodes from the multiple circuit nodes, wherein the multiple initial nodes include at least boundary nodes, branch nodes, and link nodes.

[0054] Specifically, the network structure of the power distribution system is comprehensively analyzed to identify all circuit nodes in the system. These nodes can be load nodes, power supply nodes, or any connection points that may affect the current and voltage distribution.

[0055] Based on all the identified circuit nodes, multiple initial nodes are determined from multiple circuit nodes, and the selection of the initial nodes is based on their special positions in the network and their potential impact on the harmonic current path. The multiple initial nodes include at least boundary nodes, branch nodes and link nodes, among which the boundary nodes are located at the edge of the distribution network. They are the interface for harmonic currents to enter and exit the distribution network, which is crucial to the optimization of the measurement range; the branch nodes are located at the branch points of the network, and they can help analyze the distribution path of the current and provide information on the possible flow direction of the harmonic current; the link nodes are located on the chain structure separated by the boundary nodes and the branch nodes. Although their measurement information is of low value under low observable conditions (i.e., the measurement data of the distribution system is not sufficient to fully describe or determine the state of the distribution system), they can assist in building a complete network model as connecting nodes, which indirectly contributes to the accuracy and comprehensiveness of harmonic source positioning.

[0056] For example, Figure 2 Schematic diagram of three types of nodes on a radial feeder according to one embodiment of the present invention. Figure 2 The figure shows the node location distribution in the IEEE33 node system (a widely used distribution system model proposed by the IEEE (Institute of Electrical and Electronics Engineers)). The nodes in the system are divided into the following three categories according to their locations: boundary nodes, such as node 1, node 18, node 22, node 25, and node 33; branch nodes, such as node 2, node 3, and node 6; link nodes, that is, other nodes in the node system except boundary nodes and branch nodes, such as node 4, node 5, node 7, node 8, and node 9. The boundary nodes are located at the network boundary. Due to the harmonic unidirectional transmission characteristics of the radial topology, installing PMUs is conducive to maximizing the measurement range; branch nodes are located at the branches, and installing PMUs is conducive to mastering the specific paths of harmonic currents; link nodes are all located on the chain structure separated by boundary nodes and branch nodes. The measurement information value is low and it is easy to be associated with the measurement information of upstream and downstream boundary nodes and branch nodes. PMUs are selectively configured for link nodes, such as installing them at the busbar containing critical loads or harmonic sources.

[0057] As an optional implementation, obtaining harmonic current information of multiple initial nodes includes: obtaining multiple initial sections of the distribution system based on the multiple initial nodes; determining multiple balancing nodes from the multiple initial sections; and measuring current information of the multiple balancing nodes to obtain harmonic current information.

[0058] Specifically, the acquisition of the initial section is completed by positioning a plurality of initial nodes, and the boundary nodes and branch nodes divide the entire power distribution system into a plurality of chain-shaped or branch-shaped initial sections.

[0059] For example, Figure 3FIG. 1 is a schematic diagram of a hierarchical estimation algorithm system partitioning method according to one embodiment of the present invention. Figure 3 As shown in (a), the entire system is divided into 7 initial segments through boundary nodes 1, 18, 22, 25, 33 and branch nodes 2, 3, 6, namely: segment I, segment II, segment III, segment IV, segment V, segment VI and segment VII.

[0060] In addition, the balancing node is a special node in the power system analysis, which is used to provide the voltage reference value of the system and provide the power balance condition in the calculation. In each initial section, one or more nodes are selected as balancing nodes, which are usually nodes connected to the system power supply or have a higher voltage or power level in the section. For example, in Figure 3 In (a), node l is designated as a balancing node in the IEEE 33-node system because it provides a reference for the system voltage.

[0061] Specifically, on the basis of determining the balancing node, a measuring device, such as a PMU, is used to measure the current information of multiple balancing nodes to obtain the harmonic current information.

[0062] It should be noted that the flow path of harmonic current in the system starts from the balancing node and propagates along the branch to other nodes. Therefore, by measuring the harmonic current information of the balancing node, the occurrence location of the harmonic current and its possible propagation path can be preliminarily determined.

[0063] As an optional implementation, obtaining multiple initial sections of the power distribution system based on multiple initial nodes includes: classifying multiple circuit nodes based on the initial nodes to obtain multiple node sets; performing clustering topology operations on the multiple node sets to obtain multiple initial sections.

[0064] Specifically, based on the determined initial node, multiple circuit nodes in the power distribution system are classified to obtain multiple node sets. Exemplarily, the multiple circuit nodes are divided into three categories, namely: boundary nodes, branch nodes and link nodes.

[0065] Specifically, all branches belonging to the same link are aggregated into an equivalent branch and renumbered to simplify the network model, reduce the number of nodes and branches, and improve the computational efficiency of state estimation.

[0066] For example, Figure 3 As shown in (a) in the figure, the boundary nodes in the system are renumbered, and the corresponding relationship between the new node numbers and the old node numbers is shown in Table 1.

[0067] Table 1 Correspondence table of new and old node numbers

[0068]

[0069] For example, Figure 3 As shown in (b), Figure 3 (b) in the figure performs a clustering topology operation on multiple node sets to obtain multiple initial segments.

[0070] As an optional implementation, determining the target section based on harmonic current information includes: obtaining a target measurement matrix set based on the harmonic current information; generating an initial harmonic state estimation model based on the target measurement matrix set; determining a target node based on the initial harmonic state estimation model; and determining a target section based on the target node.

[0071] Specifically, a target measurement matrix set is constructed based on the collected harmonic current information. The measurement matrix reflects the mathematical relationship between the measurement equipment (such as PMU) and the system state variables (harmonic currents and harmonic voltages of nodes and branches), and is the basis for state estimation.

[0072] It should be noted that, under low observable conditions, in order to build a more effective and easier to solve model, it is necessary to screen the data in the measurement matrix. The branch current measurement data of the initial section balancing node is selected as an example, because these data can more directly reflect the harmonic current path and the location of the potential harmonic source.

[0073] The initial harmonic state estimation model is generated by using the screened measurement matrix set and the grid topology information. The model describes the harmonic state of the system through the relationship between the measurement matrix, the measurement equation matrix established by network analysis, and the state variable matrix.

[0074] When building the model, it is also necessary to combine the physical characteristics of the power grid, such as node current constraints, branch current constraints, and node voltage constraints, to ensure the rationality and accuracy of the model. These constraints reflect the physical laws of power system operation and help the model accurately estimate the harmonic state.

[0075] Specifically, the basic model for harmonic state estimation of distribution system under low observability is constructed as follows:

[0076] For a power grid with n nodes and I branches, the basic mathematical model for estimating the hth harmonic state is:

[0077] Z(h)=H(h)X(h)+ε(1)

[0078] Where Z(h) represents the p×I-dimensional measurement matrix; H(h) represents the p×q-dimensional measurement matrix; the matrix X(h) represents the q×I-dimensional state variable matrix; ε represents the p×I-dimensional measurement error; p represents the number of measurements, and q represents the number of state variables to be determined.

[0079] Harmonic state estimation can be achieved by solving the following optimization problem and taking the state with the minimum measurement error as the estimation result:

[0080]

[0081] The state variable matrix X(h) contains the node and branch harmonic currents and node harmonic voltages, and its expression is:

[0082] x(h)=[(I N (h)) T (V(h)) T (I L (h)) T ] T (3)

[0083] In the formula, I N (h), I L (h) is the h-order node harmonic current vector of all nodes and branches; V(h) is the h-order node harmonic voltage vector of all nodes.

[0084] The expression of the measurement matrix Z(h) is:

[0085]

[0086] Wherein, the superscript m represents the measured value, which is used to distinguish between state quantity and quantity measurement. If a node is equipped with a PMU device, its node voltage and the current of the connected branch are measured.

[0087] According to the expressions of X(h) and Z(h), the measurement matrix H(h) can also be expressed as a block matrix, as follows:

[0088]

[0089] In the formula, and is a 01 matrix. When the branch current / node voltage is measured, the corresponding position element is set to 1, otherwise it is 0; Y(h) is the hth harmonic admittance matrix between node current and node voltage; Y prime (h) represents the hth harmonic admittance matrix between branch current and node voltage.

[0090] If H(h) is of full rank, equation (2) has a unique solution and the system is completely observable (the state of a system can be uniquely determined directly or indirectly from its measurement data); otherwise, the system is not completely observable (the measurement data does not cover all state variables). Under the condition of incomplete observability, the measurement data cannot cover all nodes and is insufficient to establish an exactly or overdetermined equation. To this end, the matrix G(h) can be introduced in combination with the topological information of the system to establish the association between the harmonic state and the measurement of the unobserved nodes / branches. For branches without PMUs, the relationship between the harmonic node voltage and the branch harmonic current can be captured by the following equation:

[0091]

[0092] Where I is the l×l dimensional unit matrix. Equation (6) can effectively increase the coupling between state quantities. After rearrangement, we can get:

[0093] 0=G(h)X(h) (7)

[0094] In the formula, the matrix G(h) represents the node harmonic voltage V(h) and branch harmonic current I without PMU. L (h), establish the connection between state variables through G(h), and incorporate unobservable variables into the analysis.

[0095] Furthermore, the augmented mathematical model of harmonic state estimation under low observability conditions can be established as follows:

[0096]

[0097] Harmonic voltage / current distribution characteristic constraints:

[0098] (a) The constraints of the node current are expressed as follows:

[0099] -Md≤I N (h)≤Md (9)

[0100] In the formula, M is a very large number, which can be taken as the maximum harmonic current amplitude that may appear in the system; d is used to indicate whether the node is assumed to be a harmonic source, and its value is as follows:

[0101]

[0102] For nodes that are not on the harmonic transmission path, M and d form an upper bound of 0 and a lower bound of 0; for harmonic injection nodes, M can effectively constrain the upper and lower bounds of the harmonic current and reduce the optimization range.

[0103] (b) The branch current constraints are expressed as follows:

[0104] -MΨ(1-d)≤AI L(h)≤MΨ(1-d) (11)

[0105] Where A is a u×l-dimensional 01 matrix used to extract {L\L k}, u represents the branch current that is not in the harmonic transmission path; Ψ is a u×n dimensional 01 matrix, with only one element in each row being 1, which is used to give {L\L k Formula (11) limits the harmonic current of the branch on the non-harmonic transmission path to 0 without affecting the harmonic current value of the branch on the harmonic transmission path.

[0106] (c) The node voltage constraints are expressed as follows:

[0107] -MΦ(1-d)≤BV(h)≤MΦ(1-d) (12)

[0108] Where B is a w×n dimensional matrix, which is used to extract {N\Nk} nodes. In each row, only one pair of corresponding elements of adjacent nodes are set to ±1 to calculate the voltage drop between nodes. w represents the total number of nodes that are not in the harmonic transmission path. Φ is a w×n dimensional 01 matrix, which has only one element set to 1 in each row, which is used to give {N\N k} imposes constraints on adjacent nodes.

[0109] In summary, the harmonic state estimation problem of distribution system under low observability can be expressed as the solution of the following mixed integer programming problem:

[0110]

[0111] Subject to the constraints of formulas (3), (9), (10), (11), (12).

[0112] Traverse the possible values ​​of d, solve the above optimization problems in turn, take the d value when the target value is optimal as the harmonic source position, and the corresponding X(h) is the harmonic state estimation result.

[0113] Based on the above analysis, the initial harmonic state estimation model is established as follows:

[0114]

[0115] Subject to the constraints of formulas (3), (9), (10), (11), (12).

[0116] In the formula,

[0117] Z1(h)=[I L1 (h), I L2 (h),…,I L7 (h)] T (15)

[0118]

[0119]

[0120] By solving the mixed integer quadratic programming problem described in equation (14), the harmonic current path and the target section where the harmonic source is located can be determined.

[0121] It should be noted that since the initial harmonic state estimation model focuses on harmonic current path identification, all voltage measurement results are discarded.

[0122] As an optional implementation, determining the location information of the target harmonic source from multiple target links according to the target measurement matrix set includes: determining the first initial node and the second initial node of the target section; obtaining the first harmonic current information of the first initial node and the second harmonic current information of the second initial node; and determining the location information of the target harmonic source from multiple target links based on the first harmonic current information, the second harmonic current information and the target measurement matrix set.

[0123] Specifically, for each target section, nodes at both ends are determined as a first initial node and a second initial node. Usually, these two nodes are the starting point and the ending point of the section and are equipped with PMUs or corresponding measurement equipment.

[0124] After the first and second initial nodes are determined, the harmonic current information is collected by PMUs or other measurement devices installed on these nodes. Exemplarily, the harmonic current phasor of the first initial node and the harmonic current phasor of the second initial node are obtained.

[0125] The first harmonic current information of the first initial node and the second harmonic current information of the second initial node are combined with the previously constructed target measurement matrix set to form a more detailed measurement data set. These data will be used to construct the second-level harmonic state estimation model (target harmonic state estimation model) to determine the specific location of the harmonic source.

[0126] For example, Figure 3 FIG. 1 is a schematic diagram of a hierarchical estimation algorithm system partitioning method according to one embodiment of the present invention. Figure 3 (b) Figure 3 As shown in (c) of Figure 1, the initial harmonic state estimation model is used to determine the harmonic source in Figure 3 On this basis, the second-layer harmonic state estimation model is used to further determine the specific position of the harmonic source in the target section.

[0127] As an optional implementation, determining the location information of the target harmonic source based on the first harmonic current information, the second harmonic current information and the target measurement matrix set includes: establishing a state relationship matrix based on the first harmonic current information and the second harmonic current information; generating a target harmonic state estimation model based on the state relationship matrix and the target measurement matrix set; and determining the location information of the target harmonic source based on the target harmonic state estimation model.

[0128] Specifically, the target harmonic state estimation model can be expressed as formula (13). Solve the mixed integer programming problem described in formula (13), traverse all possible values ​​of d, and take the d value when the target value is optimal as the position of the target harmonic source.

[0129] Another specific embodiment of this scheme is as follows:

[0130] Under low observable conditions, the harmonic current injected by the node is estimated, the harmonic source in the distribution network is located, and the simulation software is used to simulate the Figure 2 The IEEE 33-node harmonic power flow program shown in Figure 2 simulates the operation of the distribution network and solves the harmonic state estimation problem based on mixed integer quadratic programming. Figure 2 As shown, node 1 is a balancing node, nodes 2-33 are load nodes, and the current source model is used to simulate the harmonic current injected into the node by the harmonic source. 1-4 nodes are set to access the current source as the harmonic source nodes in the system. The low observability condition is established by reducing the number of measurement devices. It is assumed that 8 PMUs are installed in the system, located at nodes 1, 2, 3, 6, 18, 22, 25 and 33, for measuring node harmonic voltage phasors and branch harmonic current phasors. The harmonic voltage value of each node and the branch harmonic current value are calculated using the harmonic power flow program, and Gaussian noise signals are added to obtain the measurement value database. According to the installation of the PMU, some measurement values ​​are selected from the library to construct the measurement matrix of the harmonic state estimation problem.

[0131] The root mean square error (RMSE) is used as a measure of the accuracy of harmonic source location. The estimated value of the node harmonic current obtained by the harmonic state estimation is compared with the actual value of the node harmonic current. The smaller the root mean square error, the smaller the difference between the estimated value and the actual value, that is, the more accurate the harmonic state estimation result is. The root mean square error formula is as follows:

[0132]

[0133] In the formula, I N (h) is the true value of the node harmonic current, is the estimated value of the node harmonic current, i is the node number, and n is the total number of nodes.

[0134] In the same simulation environment, the method proposed in this application and the prior art are used to perform harmonic state estimation simulation. The simulation results show that the root mean square error corresponding to the method proposed in this application is smaller than the root mean square error corresponding to the prior art, that is, the method for determining the harmonic source position proposed in this application is more accurate than the prior art when performing harmonic state estimation.

[0135] Through the description of the above implementation methods, those skilled in the art can clearly understand that the method according to the above embodiment can be implemented by means of software plus a necessary general hardware platform, and of course can also be implemented by hardware, but in many cases the former is a better implementation method. Based on such an understanding, the technical solution of the present invention is essentially or the part that contributes to the prior art can be embodied in the form of a software product, which is stored in a storage medium (such as ROM / RAM, a magnetic disk, or an optical disk), and includes a number of instructions for a terminal device (which can be a mobile phone, a computer, a server, or a grid device, etc.) to execute the methods of various embodiments of the present invention.

[0136] In this embodiment, a device for determining the location of a harmonic source in a distribution network is also provided, and the device is used to implement the above-mentioned embodiments and preferred implementation modes, and the descriptions that have been made will not be repeated. As used below, the term "module" can implement a combination of software and / or hardware of a predetermined function. Although the devices described in the following embodiments are preferably implemented in software, the implementation of hardware, or a combination of software and hardware, is also possible and conceivable.

[0137] Figure 4 is a structural block diagram of a device 400 for determining the harmonic source position of a distribution network according to one embodiment of the present invention, such as Figure 4 As shown, the device includes: a first acquisition module 401, a first determination module 402 and a second determination module 403.

[0138] A first acquisition module 401 is used to acquire harmonic current information of a plurality of initial nodes in a power distribution system, wherein the plurality of initial nodes are nodes equipped with a measurement device;

[0139] A first determination module 402 is used to determine a target section according to harmonic current information, wherein the target section includes a plurality of target links;

[0140] The second determination module 403 is used to determine the location information of the target harmonic source from the multiple target links according to the target measurement matrix set, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix and a state variable matrix.

[0141] Optionally, the device 400 for determining the harmonic source position also includes: a second acquisition module, used to acquire multiple circuit nodes of the distribution system; and a third determination module, used to determine multiple initial nodes from the multiple circuit nodes, wherein the multiple initial nodes include at least boundary nodes, branch nodes, and link nodes.

[0142] Optionally, the first acquisition module 401 includes: a first acquisition unit, used to acquire multiple initial sections of the distribution system based on multiple initial nodes; a first determination unit, used to determine multiple balancing nodes from the multiple initial sections; and a measurement unit, used to measure current information of multiple balancing nodes to obtain harmonic current information.

[0143] Optionally, the first acquisition unit includes: a classification subunit, used to classify multiple circuit nodes based on the initial node to obtain multiple node sets; and an execution subunit, used to perform a clustering topology operation on the multiple node sets to obtain multiple initial segments.

[0144] Optionally, the first determination module 402 includes: a second acquisition unit, used to acquire a target measurement matrix set based on harmonic current information; a generation unit, used to generate an initial harmonic state estimation model based on the target measurement matrix set; a second determination unit, used to determine a target node based on the initial harmonic state estimation model; and a third determination unit, used to determine a target section based on the target node.

[0145] Optionally, the second determination module 403 includes: a fourth determination unit, used to determine the first initial node and the second initial node of the target segment; a third acquisition unit, used to acquire the first harmonic current information of the first initial node and the second harmonic current information of the second initial node; a fifth determination unit, used to determine the location information of the target harmonic source from multiple target links based on the first harmonic current information, the second harmonic current information and the target measurement matrix set.

[0146] Optionally, the fifth determination unit includes: an establishment subunit, used to establish a state relationship matrix based on the first harmonic current information and the second harmonic current information; a generation subunit, used to generate a target harmonic state estimation model based on the state relationship matrix and the target measurement matrix set; and a determination subunit, used to determine the location information of the target harmonic source based on the target harmonic state estimation model.

[0147] An embodiment of the present invention further provides an electronic device, including a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the above-mentioned method for determining the location of a harmonic source in a power distribution network.

[0148] Optionally, in this embodiment, the electronic device may be configured to store a computer program for performing the following steps:

[0149] Step S102, obtaining harmonic current information of a plurality of initial nodes in the power distribution system, wherein the plurality of initial nodes are nodes equipped with a measuring device;

[0150] Step S104, determining a target section according to the harmonic current information, wherein the target section includes a plurality of target links;

[0151] Step S106, determining the location information of the target harmonic source from the multiple target links according to the target measurement matrix set, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix, and a state variable matrix.

[0152] Optionally, when the processor executes the program, the following steps are also implemented: obtaining multiple circuit nodes of the power distribution system; determining multiple initial nodes from the multiple circuit nodes, wherein the multiple initial nodes include at least boundary nodes, branch nodes and link nodes.

[0153] Optionally, when the processor executes the program, the following steps are also implemented: obtaining multiple initial sections of the distribution system based on multiple initial nodes; determining multiple balancing nodes from the multiple initial sections; and measuring current information of the multiple balancing nodes to obtain harmonic current information.

[0154] Optionally, when executing the program, the processor further implements the following steps: classifying multiple circuit nodes based on the initial node to obtain multiple node sets; performing clustering topology operations on the multiple node sets to obtain multiple initial segments.

[0155] Optionally, when the processor executes the program, the following steps are also implemented: obtaining a target measurement matrix set based on harmonic current information; generating an initial harmonic state estimation model based on the target measurement matrix set; determining a target node based on the initial harmonic state estimation model; and determining a target section based on the target node.

[0156] Optionally, when the processor executes the program, the following steps are also implemented: determining a first initial node and a second initial node of the target segment; obtaining first harmonic current information of the first initial node and second harmonic current information of the second initial node; and determining location information of the target harmonic source from multiple target links based on the first harmonic current information, the second harmonic current information and the target measurement matrix set.

[0157] Optionally, when the processor executes the program, the following steps are also implemented: establishing a state relationship matrix based on the first harmonic current information and the second harmonic current information; generating a target harmonic state estimation model based on the state relationship matrix and the target measurement matrix set; and determining the location information of the target harmonic source based on the target harmonic state estimation model.

[0158] An embodiment of the present invention further provides a computer-readable storage medium, in which a computer program is stored, wherein the computer program is configured to execute the above-mentioned method for determining the location of harmonic sources in a distribution network when running on a computer or a processor.

[0159] Optionally, in this embodiment, the computer-readable storage medium may be configured to store a computer program for performing the following steps:

[0160] Step S102, obtaining harmonic current information of a plurality of initial nodes in the power distribution system, wherein the plurality of initial nodes are nodes equipped with a measuring device;

[0161] Step S104, determining a target section according to the harmonic current information, wherein the target section includes a plurality of target links;

[0162] Step S106, determining the location information of the target harmonic source from the multiple target links according to the target measurement matrix set, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix, and a state variable matrix.

[0163] Optionally, the storage medium is configured to store program code for executing the following steps: obtaining multiple circuit nodes of the power distribution system; determining multiple initial nodes from the multiple circuit nodes, wherein the multiple initial nodes include at least boundary nodes, branch nodes, and link nodes.

[0164] Optionally, the storage medium is configured to store program code for executing the following steps: obtaining multiple initial sections of the distribution system based on multiple initial nodes; determining multiple balancing nodes from the multiple initial sections; and measuring current information of the multiple balancing nodes to obtain harmonic current information.

[0165] Optionally, the storage medium is configured to store program codes for executing the following steps: classifying multiple circuit nodes based on the initial node to obtain multiple node sets; performing clustering topology operations on the multiple node sets to obtain multiple initial segments.

[0166] Optionally, the storage medium is configured to store program code for performing the following steps: obtaining a target measurement matrix set based on harmonic current information; generating an initial harmonic state estimation model based on the target measurement matrix set; determining a target node based on the initial harmonic state estimation model; and determining a target segment based on the target node.

[0167] Optionally, the storage medium is configured to store program code for performing the following steps: determining a first initial node and a second initial node of a target segment; obtaining first harmonic current information of the first initial node and second harmonic current information of the second initial node; and determining location information of a target harmonic source from multiple target links based on the first harmonic current information, the second harmonic current information, and a target measurement matrix set.

[0168] Optionally, the storage medium is configured to store program code for performing the following steps: establishing a state relationship matrix based on the first harmonic current information and the second harmonic current information; generating a target harmonic state estimation model based on the state relationship matrix and the target measurement matrix set; and determining the location information of the target harmonic source based on the target harmonic state estimation model.

[0169] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments and optional implementation modes, and this embodiment will not be described in detail here.

[0170] In the above embodiments of the present invention, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0171] In some embodiments provided in the present application, it should be understood that the disclosed technical content can be implemented in other ways. Among them, the device embodiments described above are only schematic. For example, the division of units can be a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interfaces, indirect coupling or communication connection of units or modules, which can be electrical or other forms.

[0172] The units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in one place or distributed over multiple units. Some or all of the units may be selected according to actual needs to achieve the purpose of the present embodiment.

[0173] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated unit may be implemented in the form of hardware or in the form of software functional units.

[0174] If the integrated unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, which is stored in a storage medium and includes several instructions for a computer device (which can be a personal computer, a server or a grid device, etc.) to perform all or part of the steps of the methods of various embodiments of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk, etc., which can store program codes.

[0175] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining the location of harmonic sources in a distribution network, characterized in that: Applied to a power distribution system, the method comprises: Acquiring harmonic current information of a plurality of initial nodes in the power distribution system, wherein the plurality of initial nodes are nodes equipped with a measuring device; determining a target section according to the harmonic current information, wherein the target section includes a plurality of target links; The location information of the target harmonic source is determined from the multiple target links according to the target measurement matrix set, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix, and a state variable matrix.

2. The method for determining the harmonic source position of the distribution network according to claim 1, characterized in that: The method for determining the harmonic source position of the distribution network also includes: Acquire multiple circuit nodes of the power distribution system; The plurality of initial nodes are determined from the plurality of circuit nodes, wherein the plurality of initial nodes at least include boundary nodes, branch nodes, and link nodes.

3. The method for determining the harmonic source position of the distribution network according to claim 2, characterized in that: Acquiring the harmonic current information of the multiple initial nodes includes: acquiring a plurality of initial sections of the power distribution system based on the plurality of initial nodes; determining a plurality of balancing nodes from within the plurality of initial segments; The current information of the multiple balancing nodes is measured to obtain the harmonic current information.

4. The method for determining the harmonic source position of the distribution network according to claim 3, characterized in that: Acquiring the plurality of initial sections of the power distribution system based on the plurality of initial nodes comprises: Classifying the plurality of circuit nodes based on the initial node to obtain a plurality of node sets; A clustering topology operation is performed on the plurality of node sets to obtain the plurality of initial segments.

5. The method for determining the harmonic source position of a distribution network according to claim 1, characterized in that: Determining the target section according to the harmonic current information includes: Acquire the target measurement matrix set according to the harmonic current information; generating an initial harmonic state estimation model according to the target measurement matrix set; Determining a target node based on the initial harmonic state estimation model; The target segment is determined according to the target node.

6. The method for determining the harmonic source position of a distribution network according to claim 1, characterized in that: Determining the location information of the target harmonic source from the multiple target links according to the target measurement matrix set includes: Determining a first initial node and a second initial node of the target segment; Acquire first harmonic current information of the first initial node and second harmonic current information of the second initial node; The location information of the target harmonic source is determined from the plurality of target links based on the first harmonic current information, the second harmonic current information, and the target measurement matrix set.

7. The method for determining the harmonic source position of the distribution network according to claim 6, characterized in that: Determining the location information of the target harmonic source based on the first harmonic current information, the second harmonic current information and the target measurement matrix set includes: Establishing a state relationship matrix according to the first harmonic current information and the second harmonic current information; Generate a target harmonic state estimation model according to the state relationship matrix and the target measurement matrix set; The position information of the target harmonic source is determined based on the target harmonic state estimation model.

8. A device for determining the location of harmonic sources in a distribution network, characterized in that: Applied to a power distribution system, the device comprises: A first acquisition module, configured to acquire harmonic current information of a plurality of initial nodes in the power distribution system, wherein the plurality of initial nodes are nodes equipped with a measurement device; A first determination module, configured to determine a target section according to the harmonic current information, wherein the target section includes a plurality of target links; The second determination module is used to determine the location information of the target harmonic source from the multiple target links according to the target measurement matrix set, wherein the target measurement matrix set includes a first-dimensional measurement matrix, a second-dimensional measurement matrix and a state variable matrix.

9. An electronic device comprising a memory and a processor, characterized in that: The memory stores a computer program, and the processor is configured to run the computer program to execute the method for determining the location of a harmonic source in a power distribution network as described in any one of claims 1 to 7.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores a computer program, wherein the computer program is configured to execute the method for determining the location of a harmonic source in a distribution network as described in any one of claims 1 to 7 when running on a computer or a processor.

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