Harmonic source positioning method and system based on H-infinity filtering method

Abstract

The invention discloses a harmonic source positioning method and system based on an H-infinity filtering method. The method comprises the following steps: establishing a measurement equation based on measurement information; estimating the injection harmonic current of each node based on an H-infinity filtering method; and positioning the harmonic source according to the estimation result of the injected harmonic current. According to the method, when the harmonic source of the power system is positioned under the access of a large-scale new energy node, the condition that the harmonic state estimation is inaccurate due to the fact that a model is difficult to accurately acquire and noise information is difficult to accurately acquire can be handled, the positioning of the harmonic source can still be normally completed, and the harmonic state estimation error is very small.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality monitoring, and in particular to a harmonic source locating method and system based on an H∞ filtering method. Background Art

[0002] In recent years, with the rapid progress of power electronics technology, new energy sources such as photovoltaics and wind power have been widely developed. However, there are significant differences between the power system with a high proportion of new energy access and the traditional power system. In particular, renewable energy sources such as photovoltaics and wind power use power electronic equipment as interfaces. When they are widely used, they will introduce a large number of harmonics, causing harmonics to propagate in the power system, which may cause failures of relay protection and automatic devices, interfere with communication systems, and cause serious economic losses.

[0003] Harmonic State Estimation (HSE) is an inverse process for inferring harmonic power flows. It measures the harmonic voltage and harmonic current of each bus and branch in the power grid through a limited number of synchronous harmonic measurement devices, without directly monitoring the harmonic state of all nodes and branches, thereby reducing costs.

[0004] Early harmonic state estimation methods were mainly based on the least squares method proposed by Heydt. However, subsequent researchers proposed the robust total least squares method to improve the ability to suppress gross errors. However, these methods all have the problem of poor real-time performance and are difficult to cope with the dynamic changes in power system operation. To this end, some methods such as Kalman filtering (Multi-function grid-connected inverter, MFGTI), extended Kalman filtering (Extended Kalman Filter, EKF) and unscented Kalman filtering (Unscented Kalman Filter, UKF) have been proposed and widely used. However, these algorithms perform poorly when the model and noise statistics are inaccurate. Summary of the invention

[0005] In view of the above-mentioned problems, the present invention is proposed.

[0006] Therefore, the technical problem solved by the present invention is: how to ensure the accuracy and anti-interference performance of estimation when the measuring device is abnormally interfered, and ensure the accuracy of harmonic source positioning.

[0007] In order to solve the above technical problems, the present invention provides the following technical solutions: a harmonic source location method based on H∞ filtering method, comprising:

[0008] Establishing measurement equations based on measurement information;

[0009] Estimate the injected harmonic current of each node based on the H∞ filtering method;

[0010] The harmonic source is located based on the injected harmonic current estimation results.

[0011] As a preferred solution of the harmonic source location method based on the H∞ filtering method described in the present invention, the measurement information includes the state quantity of the harmonic current injected into all nodes obtained through the power grid topology.

[0012]

[0013] in, represents the hth harmonic state vector at time k, represents the hth harmonic state estimation vector of the mth node at time k, Elements in

[0014] Obtain harmonic measurement data vector according to the harmonic monitoring device

[0015]

[0016] in, It represents the harmonic measurement vector of order h at time k, which is composed of the harmonic voltage phasor and harmonic current phasor data uploaded by the harmonic monitoring device. express The elements in represent the hth harmonic measurement vector of the mth node at time k.

[0017] As a preferred solution of the harmonic source location method based on the H∞ filtering method described in the present invention, the measurement equation includes injecting harmonic current through the node to be estimated, establishing the state transfer equation of the H∞ filter, and the formula is expressed as follows;

[0018]

[0019] in, represents the hth harmonic state transfer matrix at the kth moment; w k represents the process noise at time k;

[0020] Establish the H∞ filter measurement equation according to the topological structure that needs harmonic state estimation;

[0021]

[0022] in, represents the hth harmonic measurement matrix at the kth moment, that is, the mathematical relationship between the state quantity to be estimated and the quantity measurement, v k represents the measurement noise at time k.

[0023] As a preferred solution of the harmonic source locating method based on the H∞ filtering method described in the present invention, wherein: the H∞ filtering method includes, the H infinity filtering state quantity extrapolation formula is expressed as:

[0024]

[0025] in, represents the state transfer matrix, express The posterior estimate of is obtained by the state value update step in the subsequent step, Representing a priori A priori estimate.

[0026] As a preferred solution of the harmonic source location method based on the H∞ filtering method described in the present invention, the state value updating step includes calculating the H∞ filtering gain matrix The formula is:

[0027]

[0028] in, represents the hth harmonic estimation error covariance matrix at the kth time, and λ represents H ∞ Filter performance boundary, R -1 represents the measurement noise covariance matrix;

[0029] Update of status value The formula is:

[0030]

[0031] in, express The posterior estimate of .

[0032] As a preferred solution of the harmonic source location method based on the H∞ filtering method described in the present invention, wherein: the estimation result includes, the updated estimation error covariance formula is expressed as:

[0033]

[0034] in, represents the noise covariance matrix of the hth harmonic process at time k;

[0035] Update harmonic state estimates The formula is:

[0036]

[0037] Determine whether all harmonic orders to be estimated have been estimated. If not, select the next harmonic order and start again by establishing the measurement equation based on the measurement information. If all harmonic orders have been estimated, output the result.

[0038] As a preferred solution of the harmonic source locating method based on the H∞ filtering method described in the present invention, wherein: the locating of the harmonic source includes determining the injection node position of the hth harmonic source at time k according to the harmonic state estimation result and the set threshold;

[0039]

[0040] in, It indicates the selected harmonic source judgment threshold, and its specific value is set according to the structure, capacity and voltage level parameters of the power grid.

[0041] A harmonic source positioning system based on an H∞ filtering method using any method described in the present invention, wherein:

[0042] The data acquisition module collects harmonic voltage and current data from each node of the power grid and transmits the data to the data processing module through the data transmission interface;

[0043] The data processing module performs Fourier transform on the collected data, extracts the amplitude and phase information of each harmonic, and performs data cleaning and feature extraction;

[0044] The state estimation module applies the H∞ filtering method to perform state estimation based on the extracted feature data, constructs a state transfer model, calculates the filter gain, and updates the state estimation result;

[0045] The harmonic source positioning module determines the location of the harmonic source injection node according to the state estimation result and the set threshold, and displays the positioning result through the result display unit.

[0046] A computer device comprises: a memory and a processor; the memory stores a computer program, wherein the processor implements the steps of any one of the methods of the present invention when executing the computer program.

[0047] A computer-readable storage medium stores a computer program, wherein the computer program, when executed by a processor, implements the steps of any one of the methods of the present invention.

[0048] The beneficial effects of the present invention are as follows: when locating harmonic sources in the power system under the access of large-scale new energy sources, the model is difficult to obtain accurately, the noise information is difficult to obtain accurately, resulting in inaccurate harmonic state estimation, the positioning of the harmonic source can still be completed normally and the error of the harmonic state estimation is very small. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. Among them:

[0050] Figure 1 An overall flow chart of a harmonic source location method based on an H∞ filtering method provided by the first embodiment of the present invention;

[0051] Figure 2 A basic process of H∞ filtering harmonic state estimation of a harmonic source location method based on an H∞ filtering method provided by the first embodiment of the present invention;

[0052] Figure 3 An IEEE14 node structure diagram of a harmonic source location method based on an H∞ filtering method provided in a second embodiment of the present invention;

[0053] Figure 4 The fifth harmonic estimation result of harmonic node 10 of a harmonic source location method based on an H∞ filtering method provided by the second embodiment of the present invention;

[0054] Figure 5 The fifth harmonic estimation result of harmonic node 13 of a harmonic source location method based on the H∞ filtering method provided by the second embodiment of the present invention;

[0055] Figure 6 A fifth harmonic estimated phase angle error result of harmonic node 10 of a harmonic source location method based on an H∞ filtering method provided by a second embodiment of the present invention;

[0056] Figure 7 A fifth harmonic estimated phase angle error result of harmonic node 13 of a harmonic source location method based on an H∞ filtering method provided in a second embodiment of the present invention;

[0057] Figure 8 The fifth harmonic estimation amplitude error result of all nodes of the harmonic source location method based on the H∞ filtering method provided by the second embodiment of the present invention. DETAILED DESCRIPTION

[0058] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0059] Example 1

[0060] Reference Figure 1-Figure 2 , is an embodiment of the present invention, and provides a harmonic source location method based on the H∞ filtering method, comprising:

[0061] S1: Establish measurement equations based on measurement information.

[0062] Further, such as Figure 1 As shown, the measurement information includes the state quantity of harmonic current injected into all nodes obtained through the power grid topology.

[0063]

[0064] in, represents the hth harmonic state vector at time k, represents the hth harmonic state estimation vector of the mth node at time k, The elements in .

[0065] Furthermore, the harmonic measurement data vector is obtained according to the harmonic monitoring device. The formula is:

[0066]

[0067] in, It represents the harmonic measurement vector of order h at time k, which is composed of the harmonic voltage phasor and harmonic current phasor data uploaded by the harmonic monitoring device. express The elements in represent the hth harmonic measurement vector of the mth node at time k.

[0068] Furthermore, the measurement equation includes injecting harmonic current through the node to be estimated and establishing the state transfer equation of H∞ filtering, which is expressed as follows:

[0069]

[0070] in, represents the hth harmonic state transfer matrix at the kth moment; w k represents the process noise at time k.

[0071] Furthermore, the H∞ filter measurement equation is established according to the topological structure of the harmonic state estimation, and the formula is expressed as follows:

[0072]

[0073] in, represents the hth harmonic measurement matrix at the kth moment, that is, the mathematical relationship between the state quantity to be estimated and the quantity measurement, v k represents the measurement noise at time k.

[0074] It should be noted that by acquiring the harmonic current and voltage data of each node in the power grid, the measurement equation is established to provide basic data for subsequent state estimation. The establishment of the measurement equation enables the system to monitor the harmonic situation in the power grid in real time, improving the accuracy and real-time performance of harmonic source positioning. It solves the high cost and complexity of harmonic monitoring of all nodes and branches in the traditional method, and performs state estimation through limited measurement data, effectively reducing costs and complexity.

[0075] S2: Estimate the injected harmonic current of each node based on the H∞ filtering method.

[0076] Furthermore, the H∞ filtering method includes that the H∞ filtering state quantity extrapolation formula is expressed as:

[0077]

[0078] in, represents the state transfer matrix, express The posterior estimate of is obtained by the state value update step in the subsequent step, Representing a priori A priori estimate.

[0079] Furthermore, the state value updating step includes calculating the H∞ filter gain matrix The formula is:

[0080]

[0081] in, represents the hth harmonic estimation error covariance matrix at the kth time, and λ represents H ∞ Filter performance boundary, R -1 represents the measurement noise covariance matrix.

[0082] Furthermore, the state value is updated The formula is:

[0083]

[0084] in, express The posterior estimate of .

[0085] It should be noted that the H∞ filtering method is highly robust to noise and model uncertainty, and can provide accurate state estimation in complex power grid environments. State estimation using the H∞ filtering method can maintain high estimation accuracy when noise information is uncertain. Traditional Kalman filtering methods perform poorly when noise and model inaccuracies occur. The H∞ filtering method improves the accuracy and robustness of state estimation by processing noise and model uncertainty.

[0086] S3: Locate the harmonic source based on the injected harmonic current estimation result.

[0087] Furthermore, the estimation result includes an updated estimation error covariance formula expressed as:

[0088]

[0089] in, represents the noise covariance matrix of the hth harmonic process at time k.

[0090] Furthermore, the harmonic state estimate is updated The formula is:

[0091]

[0092] Furthermore, it is determined whether the harmonic order to be estimated has been fully estimated. If not, the next harmonic order is selected to start again from establishing the measurement equation according to the measurement information. If it has been fully estimated, the result is output.

[0093] Furthermore, the positioning of the harmonic source includes determining the injection node position of the hth harmonic source at time k according to the harmonic state estimation result and the set threshold, which is expressed as follows:

[0094]

[0095] in, It indicates the selected harmonic source judgment threshold, and its specific value is set according to the structure, capacity and voltage level parameters of the power grid.

[0096] It should be noted that by setting a threshold and combining the state estimation results, the injection node of the harmonic source can be accurately identified. This method can still work effectively under complex noise information, ensuring the reliability of harmonic source positioning. Traditional methods are prone to misjudgment of the harmonic source position when noise interference is severe. This method effectively solves the misjudgment problem caused by noise interference by setting a reasonable threshold and combining the estimation results of H∞ filtering, thereby improving the accuracy of harmonic source positioning.

[0097] On the other hand, this embodiment also provides a harmonic source positioning system based on the H∞ filtering method, which includes:

[0098] The data acquisition module collects harmonic voltage and current data from each node of the power grid and transmits the data to the data processing module through the data transmission interface.

[0099] The data processing module performs Fourier transform on the collected data, extracts the amplitude and phase information of each harmonic, and performs data cleaning and feature extraction.

[0100] The state estimation module applies the H∞ filtering method to perform state estimation based on the extracted feature data, constructs a state transfer model, calculates the filter gain, and updates the state estimation result.

[0101] The harmonic source positioning module determines the location of the harmonic source injection node according to the state estimation result and the set threshold, and displays the positioning result through the result display unit.

[0102] If the above functions are implemented in the form of software functional units and sold or used as independent products, they 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 the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium, including several instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk and other media that can store program codes.

[0103] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0104] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0105] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, a plurality of steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0106] Example 2

[0107] Reference Figure 3-8 , which is an embodiment of the present invention, provides a harmonic source locating method based on the H∞ filtering method. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0108] To verify the effectiveness of the proposed harmonic source location scheme, Figure 3 As shown in the figure, the IEEE 14-node model was first established in PSCAD to evaluate the estimation performance of the H∞ filtering algorithm. The system baseline capacity was set to 100MA, and the nodes connected to the generator were determined to be 1, 2, 3, 6, and 8. The harmonic sources were placed at nodes 10 and 13, while the other buses did not contain harmonic sources, and the current source model was used to describe the harmonic sources. To ensure the observability of the system, we set up measurement devices at nodes 2, 6, 9, and 12, which are geographically and electrically far away from the harmonic sources, which is in line with the actual situation. Each measurement device is used to measure the harmonic voltage of the node and the harmonic current of the adjacent branch. Next, PSCAD was used to calculate the harmonic flow, and Gaussian noise was added to the calculation results to simulate the measurement error, and 1000 sets (200 seconds) of harmonic data were generated for analysis.

[0109] To verify the superiority under noise interference, this case gradually increases the signal-to-noise ratio of all measured data from 50dB to 30dB noise level. The H∞ filtering method of the present invention is compared with the Kalman filtering method with constant noise parameters, and the performance boundary λ is set to 5.

[0110] Attached Figure 4 To Attachment Figure 8 The estimation results of the fifth harmonic of nodes 10 and 13 are shown, as well as the estimated phase angle error and the root mean square value of the fifth harmonic of all nodes. It can be seen from the figure that under time-varying noise interference, the H∞ filtering method and the KF method are not much different in the accuracy of harmonic estimation of setting harmonic source nodes, and both can accurately estimate the harmonic level. However, the KF method produces large estimation errors on nodes 1 and 3, misjudging them as having high harmonic content, which is due to inaccurate noise information. In contrast, the H∞ filtering method has no misjudgment because it has low requirements for noise information and is provided by the attached Figure 6 , Attachment Figure 7 It can be seen that the error of the fifth harmonic phase angle estimation of the harmonic source node proposed in this paper is below 0.005° when the noise gradually increases to 30dB. When the noise gradually increases to 30dB, it is about 0.02°, which has a high accuracy. When the noise gradually increases to 30dB, it is about 0.04°, which can still meet the accuracy requirements. Figure 8 It can be seen that when setting nodes at the harmonic source, the fifth harmonic estimation error is less than 0.004pu, and the estimation errors of other nodes are all less than 0.006pu. Figure 4 , Attachment Figure 5 It can be seen that the relative error is also very small, which proves that the estimation accuracy of the method proposed in the present invention is high, and the harmonic state can be estimated under complex noise conditions, thereby completing the accurate positioning of the harmonic source.

[0111] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A harmonic source location method based on H∞ filtering method, characterized in that: include: Establishing measurement equations based on measurement information; Estimate the injected harmonic current of each node based on the H∞ filtering method; The harmonic source is located based on the injected harmonic current estimation results.

2. The harmonic source location method based on the H∞ filtering method according to claim 1, characterized in that: The measurement information includes the state quantity of harmonic current injected into all nodes obtained through the power grid topology. in, represents the hth harmonic state vector at time k, represents the hth harmonic state estimation vector of the mth node at time k, Elements in Obtain harmonic measurement data vector according to the harmonic monitoring device in, It represents the harmonic measurement vector of order h at time k, which is composed of the harmonic voltage phasor and harmonic current phasor data uploaded by the harmonic monitoring device. express The elements in represent the hth harmonic measurement vector of the mth node at time k.

3. The harmonic source location method based on the H∞ filtering method as claimed in claim 2, characterized in that: The measurement equation includes injecting harmonic current through the node to be estimated and establishing the state transfer equation of H∞ filtering, which is expressed as follows: in, represents the hth harmonic state transfer matrix at the kth moment; w k represents the process noise at time k; Establish the H∞ filter measurement equation according to the topological structure that needs harmonic state estimation; in, represents the hth harmonic measurement matrix at the kth moment, that is, the mathematical relationship between the state quantity to be estimated and the quantity measurement, v k represents the measurement noise at time k.

4. The harmonic source location method based on the H∞ filtering method as claimed in claim 3, characterized in that: The H∞ filtering method includes: the H∞ filtering state quantity extrapolation formula is expressed as: in, represents the state transfer matrix, express The posterior estimate of is obtained by the state value update step in the subsequent step, Representation prior A priori estimate.

5. The harmonic source location method based on the H∞ filtering method according to claim 4, characterized in that: The state value updating step includes calculating the H∞ filter gain matrix The formula is: in, represents the hth harmonic estimation error covariance matrix at the kth time, and λ represents H ∞ Filter performance boundary, R -1 represents the measurement noise covariance matrix; Update of status value The formula is: in, express The posterior estimate of .

6. The harmonic source location method based on the H∞ filtering method according to claim 5, characterized in that: The estimation result includes an updated estimation error covariance formula expressed as: in, represents the noise covariance matrix of the hth harmonic process at time k; Update harmonic state estimates The formula is: Determine whether all harmonic orders to be estimated have been estimated. If not, select the next harmonic order and start again by establishing the measurement equation based on the measurement information. If all harmonic orders have been estimated, output the result.

7. The harmonic source location method based on the H∞ filtering method according to claim 6, characterized in that: The locating of the harmonic source includes determining the injection node position of the hth harmonic source at time k according to the harmonic state estimation result and the set threshold value; in, It indicates the selected harmonic source judgment threshold, and its specific value is set according to the structure, capacity and voltage level parameters of the power grid.

8. A harmonic source location system based on the H∞ filtering method using the method according to any one of claims 1 to 7, characterized in that: The data acquisition module collects harmonic voltage and current data from each node of the power grid and transmits the data to the data processing module through the data transmission interface; The data processing module performs Fourier transform on the collected data, extracts the amplitude and phase information of each harmonic, and performs data cleaning and feature extraction; The state estimation module applies the H∞ filtering method to perform state estimation based on the extracted feature data, constructs a state transfer model, calculates the filter gain, and updates the state estimation result; The harmonic source positioning module determines the location of the harmonic source injection node according to the state estimation result and the set threshold, and displays the positioning result through the result display unit.

9. A computer device comprising: Memory and processor; The memory stores a computer program, characterized in that: when the processor executes the computer program, the steps of the harmonic source locating method based on the H∞ filtering method are implemented.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a harmonic source location method based on an H∞ filtering method are implemented.

Images