RLS-MRAS-based distribution line ground parameter online identification method

Abstract

The invention relates to a distribution line ground parameter online identification method based on RLS-MRAS, and the method comprises the steps: employing the neutral point voltage during the single-phase ground fault of a power distribution network and compensation current information injected by an active inverter (the active inverter in the abstract drawing takes a cascaded H bridge as an example); and taking a ground capacitance value with relatively high RLS identification precision as a known quantity in a variable model of the MRAS, identifying unknown quantities of ground leakage resistance and grounding transition resistance by utilizing an MRAS algorithm, continuously optimizing a final parameter identification result according to the deviation between a reference model and the variable model, and realizing multi-parameter accurate identification during the power distribution network grounding fault period. According to the method provided by the invention, the ground capacitance value identified by the RLS method is fed back to the variable model of the MRAS, and complementary advantages of the two algorithms are realized, so that the ground capacitance, the ground leakage resistance and the grounding transition resistance under the SPG fault working condition of the power distribution network are accurately identified.

Description

Technical Field

[0001] This invention relates to the field of power distribution line technology, and in particular to an online identification method for ground parameters of power distribution lines based on RLS-MRAS. Background Technology

[0002] As a critical component of the power system, the distribution network operates in a complex environment for extended periods, making it a high-risk area for faults. Among various fault types, single-phase grounding faults have a much higher probability of occurrence, accounting for approximately 80% of all faults. The resulting grounding current threatens power grid safety and is often suppressed by arc suppression devices. However, precise control of these devices requires accurate measurement of key parameters such as ground capacitance and leakage resistance.

[0003] Measurement of ground parameters in power distribution lines can be divided into offline and online measurements. Traditional offline measurement methods assume constant parameters, making it difficult to adapt to dynamic changes in line operating conditions, resulting in delayed measurement results. Among online measurement methods, the least squares method and its recursive form face the bottleneck of the curse of computational dimensionality as the amount of data increases. More importantly, existing single algorithms have inherent defects in multi-parameter collaborative identification: the recursive least squares method (RLS) can only guarantee the identification accuracy of ground capacitance, while it is insufficient for identifying leakage resistance and transition resistance. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide an online identification method for distribution line ground parameters based on RLS-MRAS. Under single-phase ground fault, the RLS algorithm is used to accurately identify the ground capacitance, and the ground capacitance is used as a known quantity to be fed into the MRAS algorithm to identify the unknown quantities ground leakage resistance and ground transition resistance. The final parameter identification result is continuously optimized based on the deviation between the reference model and the variable model, so as to achieve accurate identification of ground capacitance, ground leakage resistance and ground transition resistance during distribution network ground faults.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: an online identification method for ground parameters of distribution lines based on RLS-MRAS, comprising the following steps:

[0006] Step S1: When a single-phase ground fault occurs in the distribution network, sample data based on the neutral point voltage and the current injected by the active inverter. constitute ,Right now , sample data , and auxiliary model output , Combined into the system input matrix ;

[0007] Step S2: Set non-zero parameters , , and For system parameters ,Right now ,calculate To obtain the next sampling step size And calculate the prior error. ,according to Size adjustment forgetting factor ;

[0008] Step S3: Through continuous optimization and iteration in step S2, the identified system parameter estimates are... The parameters are accurately fitted using the recursive least squares method. , , and Calculate the capacitance to ground of the power distribution line. Grounding transition resistance and leakage conductivity to ground ;

[0009] Step S4: Identify the ground capacitance value with higher accuracy using the RLS algorithm. In the variable model of MRAS, which is a known input, adaptive rules are designed based on Popov's superstability theory to identify the unknown quantities of ground leakage resistance and grounding transition resistance. By continuously iterating and optimizing the final parameter identification results, the accurate identification of the distribution network's ground parameters and grounding transition resistance is achieved.

[0010] In a preferred embodiment, in step S1 and These are intermediate variables that are equivalently obtained but cannot be directly measured. They are replaced by estimates obtained through auxiliary model identification methods, and then a compensation current is injected. and neutral point voltage Specifically as follows:

[0011]

[0012] Here, the neutral point voltage is defined. For system output , This is the neutral point voltage of the distribution network. The faulty phase power supply voltage, Inject compensation current into the neutral point of the distribution network.

[0013] In a preferred embodiment, step S2 employs a variable forgetting factor strategy, dynamically adjusting based on prior error. Adjusting the forgetting factor The specific process of introducing the VFF strategy to enhance the anti-interference performance of the RLS algorithm is as follows:

[0014] Based on the analysis of the forgetting factor, the following correction function is proposed as the basis for changing the forgetting factor in this patent:

[0015]

[0016] Where S1 represents In this case, S2 represents In this situation, Indicates and The closest integer; when When the error is within an acceptable range, it means that the error is within acceptable limits. ;when When the error exceeds the specified threshold, it indicates that the error is taken as follows. The RLS algorithm with a variable forgetting factor is specifically expressed as follows:

[0017]

[0018] in, non-zero parameter , , and composition, The estimated values ​​of the system parameters identified for the next sampling step. Let covariance matrix be the variance matrix. For the gain vector, It is a forgetting factor.

[0019] In a preferred embodiment, the specific derivation of the online measurement formulas for the distribution line-to-ground parameters and ground transition conductance during a single-phase ground fault obtained in step S3 is as follows:

[0020] By reorganizing the circuit equations under the conditions of only the flexible arc suppression device and only the fault phase power supply voltage, the system output can be obtained.

[0021]

[0022] Based on the parameter identification results of the recursive least squares method , , and The relationship with ground parameters can be used to calculate the power distribution line's ground capacitance under single-phase ground fault operating conditions. Grounding transition resistance and leakage conductivity to ground The identification formula is as follows:

[0023]

[0024] in, The sampling period is very small and close to 0.

[0025] In a preferred embodiment, the specific derivation of the adaptive rule for designing MRAS based on Popov superstability theory under the single-phase ground fault condition of the distribution network in step S4 is as follows:

[0026] The ground capacitance identified in step 3 As a priori condition for the MRAS variable model, the MRAS adaptive rule designed using the Popov inequality is used to realize the ground leakage resistance. and grounding transition resistance Identification; the identified ground leakage resistance and grounding transition resistance After the next sampling step, the capacitance to ground The parameters to be identified are fed into the variable model and iteratively optimized through a closed-loop feedback mechanism, ultimately achieving the coordinated and accurate identification of the ground parameters and grounding transition resistance of the distribution line based on RLS-MRAS.

[0027] The expressions for ground capacitance, ground leakage resistance, and ground transition resistance are obtained through parameter adaptive rule estimation as follows:

[0028]

[0029]

[0030]

[0031] in, and These are estimates of the injection current and neutral point voltage. and These are estimated values ​​for capacitance to ground and leakage resistance to ground.

[0032] The present invention also provides a computer device, characterized in that it comprises:

[0033] The processor, memory, and bus, wherein the memory stores machine-readable instructions executed by the processor;

[0034] When the computer device is running, the processor communicates with the memory via a bus, and when the machine-readable instructions are executed by the processor, they perform the online identification method for power distribution line ground parameters based on RLS-MRAS as described above.

[0035] The present invention also provides a computer-readable storage medium, characterized in that it comprises:

[0036] The computer-readable storage medium contains a computer program;

[0037] The computer program is executed by the processor as described in the online identification method for ground parameters of power distribution lines based on RLS-MRAS.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. This invention utilizes known electrical quantities such as the injection current information and neutral point voltage information of the flexible arc suppression device to identify the ground parameters and transition resistance of the distribution line during ground faults. Simultaneously, the identified ground parameter values ​​are used to correct the setpoint of the injection current of the flexible arc suppression device, and combined with the proposed fuzzy control strategy for the flexible arc suppression device, the arc suppression effect under different fault conditions is further improved.

[0040] 2. This invention can realize online identification of ground parameters and ground transition resistance during ground faults, and the identification accuracy of ground parameters is not affected by transition resistance, fault location and different power distribution line parameters, which fully demonstrates that the proposed parameter identification algorithm has the advantages of both online identification and accurate identification. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of a method for online identification of ground parameters of distribution lines based on RLS-MRAS.

[0042] Figure 2 The diagram shows the zero-sequence equivalent circuit during a single-phase ground fault in a distribution network. (a) is the zero-sequence equivalent circuit, (b) is affected only by FASD, and (c) is affected only by the fault phase voltage source.

[0043] Figure 3 This is a simulation model of a 10kV distribution network containing active inverters (the active inverter in the figure is an example of a cascaded H-bridge).

[0044] Figure 4 The waveform diagrams for online identification of ground capacitance, ground leakage resistance, and ground transition resistance under a single-phase ground fault (fault point f1) are shown, where (a) is... (b) is . Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0047] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0048] This invention relates to an online identification method for ground parameters of distribution lines based on RLS-MRAS, with reference to... Figures 1 to 4 It includes the following steps:

[0049] Step S1: When a single-phase ground fault occurs in the distribution network, sample data based on the neutral point voltage and the current injected by the active inverter. constitute ,Right now , sample data , and auxiliary model output , Combined into the system input matrix Inject compensation current and neutral point voltage Specifically as follows:

[0050]

[0051] Here, the neutral point voltage is defined. For system output , This is the neutral point voltage of the distribution network. The faulty phase power supply voltage, Inject compensation current into the neutral point of the distribution network.

[0052] Step S2: Set non-zero parameters , , and For system parameters ,Right now ,calculate To obtain the next sampling step size And calculate the prior error. ,according to Size adjustment forgetting factor The specific process of introducing the VFF strategy to enhance the anti-interference performance of the RLS algorithm is as follows:

[0053] Based on the analysis of the forgetting factor, the following correction function is proposed as the basis for changing the forgetting factor in this patent:

[0054]

[0055] Where S1 represents In this case, S2 represents In this situation, Indicates and The closest integer; when When the error is within an acceptable range, it means that the error is within acceptable limits. ;when When the error exceeds the specified threshold, it indicates that the error is taken as follows: The RLS algorithm with a variable forgetting factor is expressed as follows:

[0056]

[0057] in, non-zero parameter , , and composition, The estimated values ​​of the system parameters identified for the next sampling step. Let covariance matrix be the variance matrix. For the gain vector, It is a forgetting factor.

[0058] Step S3: Through continuous optimization and iteration in step S2, the precisely identified system parameter estimates are... The parameters are accurately fitted using the recursive least squares method. , , and Calculate the capacitance to ground of the power distribution line. Grounding transition resistance and leakage conductivity to ground Specifically, it includes:

[0059] The zero-sequence equivalent circuit during a single-phase ground fault in a distribution network is as follows: Figure 2 As shown, by rearranging the circuit equations under the action of the flexible arc suppression device only and under the action of the fault phase power supply voltage only, the system output can be obtained.

[0060]

[0061] Based on the parameter identification results of the recursive least squares method , , and The relationship with ground parameters can be used to calculate the power distribution line's ground capacitance under single-phase ground fault operating conditions. Grounding transition resistance and leakage conductivity to ground The identification formula is as follows:

[0062]

[0063] in, The sampling period is very small and close to 0.

[0064] Step S4: The ground capacitance value accurately identified by the RLS algorithm is input as a known quantity into the variable model of the MRAS based on the Popov superstability theory. Through continuous iterative optimization via a closed-loop feedback mechanism, the ground leakage resistance and grounding transition resistance are accurately identified. The specific derivation of the adaptive rules for designing the MRAS based on the Popov superstability theory under the single-phase ground fault condition of the distribution network is as follows:

[0065] The ground capacitance identified in step 3 As a priori condition for the MRAS variable model, the MRAS adaptive rule designed using the Popov inequality is used to realize the ground leakage resistance. and grounding transition resistance Identification. The identified ground leakage resistance. and grounding transition resistance After the next sampling step, the capacitance to ground The parameters to be identified are fed into the variable model and iteratively optimized through a closed-loop feedback mechanism, ultimately achieving the coordinated and accurate identification of the ground parameters and grounding transition resistance of the distribution line based on RLS-MRAS.

[0066] The expressions for ground capacitance, ground leakage resistance, and ground transition resistance are obtained through parameter adaptive rule estimation as follows:

[0067]

[0068]

[0069]

[0070] in, and These are estimates of the injection current and neutral point voltage. and These are estimated values ​​for capacitance to ground and leakage resistance to ground.

[0071] In this embodiment, to verify the feasibility of the online measurement method, a simulation model was constructed using MATLAB / Simulink simulation software. The line parameters are centralized, and the 10kV distribution network simulation model built according to the topology is as follows: Figure 3 As shown. The active inverter and filter inductor are connected through a grounding transformer. The circuit is connected to the busbar, from which six feeders extend. A single-phase ground fault occurs at point f1. The 10kV distribution network is set to experience a single-phase ground fault at point f1 at 0.01s. A flexible arc suppression device injects compensation current at 0.07s. At the moment of current injection, the proposed online parameter identification algorithm is activated. The ground capacitance value identified by RLS is used as a known quantity in the MRAS variable model, and the remaining unknown parameters are identified based on adaptive rules designed according to the Popov integral inequality, thereby achieving accurate multi-parameter identification during ground faults in the distribution network. Simulation results are as follows: Figure 4 As shown.

[0072] Depend on Figure 4 It can be seen that when a ground fault with a transition resistance of 100Ω and 1kΩ occurs at fault point f1, the online identification values ​​of the ground capacitance, ground leakage resistance and ground transition resistance all approach the true values ​​infinitely.

[0073] The parameter identification method proposed in this patent can be quickly started when the flexible arc suppression device injects current, and quickly converges the parameters to be identified to near the true value. It shows good adaptability to single-phase grounding fault scenarios of distribution networks with different transition resistances, different fault locations and different line parameters, laying the foundation for accurately calculating the given value of the injected current of the flexible arc suppression device.

[0074] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. A method for on-line identification of parameters of a distribution line to ground based on RLS-MRAS, characterized in that, Comprising the following steps: Step S1: when a single-phase ground fault occurs in the power distribution network, sampling data based on the neutral point voltage and the active inverter injected current constituted , i.e. , the sampling data , and the auxiliary model output , are combined into a system input matrix ; Step S2: Set non-zero parameters , , and are system parameters , i.e. , calculate , get the next sampling step , and calculate the prior error , adjust the forgetting factor according to the size of ; Step S3: Through the continuous optimization iteration of step S2, the estimated value of the identified system parameters is , and the parameters , , and are accurately fitted according to the recursive least square method to obtain the distribution line-to-ground capacitance , the grounding transition resistance and the leakage conductance to ground ; Step S4: Identify the ground capacitance value with high accuracy by RLS algorithm The adaptive rule is designed according to the Popov hyperstability theory to identify the unknown ground leakage resistance and the ground transition resistance in the variable model of the MRAS input as a known quantity. Through continuous iteration and optimization of the final parameter identification result, the accurate identification of the ground parameters and the ground transition resistance of the distribution network is realized.

2. The method according to claim 1, wherein, The step S1 in and are equivalent acquisition and cannot be directly measured intermediate variables, replaced by the estimated value of the auxiliary model identification method, inject compensation current and neutral point voltage Specific as follows: wherein the neutral point voltage is defined as is the system output , is the neutral point voltage in the distribution network, is the fault phase supply voltage, is the compensation current injected into the neutral point of the distribution network.

3. The method according to claim 1, wherein, The step S2 adopts a variable forgetting factor strategy, dynamically adjusts the forgetting factor according to the priori error Adjusting the forgetting factor The specific process of introducing the VFF strategy to enhance the anti-interference performance of the RLS algorithm is as follows: Based on the analysis of the forgetting factor, the following correction function is proposed as the basis for changing the forgetting factor of the patent wherein S1 represents S2 represents cases, the closest integer to ; when , i.e. the error is within an acceptable range, then ; when , it indicates that the error exceeds a specified threshold, then ; the RLS algorithm with a variable forgetting factor, the specific expression is wherein is a non-zero quantity , , and consist of, is an estimate of the system parameter identified by the next sampling step size, is a covariance matrix, is a gain vector, is a forgetting factor.

4. The method according to claim 1, wherein, The specific derivation of the on-line measurement formula of the distribution line-to-ground parameter and the ground transition conductance during single-phase ground fault obtained in step S3 is as follows: The circuit equations under the action of only the flexible arc extinguishing device and under the action of only the fault-phase power supply voltage are sorted out, and the system output Parameter identification result according to recursive least square method , , and The relationship with the ground parameter can obtain the identification formula of the distribution line ground capacitance , ground transition resistance and ground leakage conductance under single-phase ground fault operating condition as follows: wherein is the sampling period, which is very small and close to 0.

5. The method according to claim 1, wherein, The specific derivation of the adaptive rule of MRAS based on Popov hyperstability theory designed for single-phase ground fault of distribution network in step S4 is as follows: The step 3 identified earth capacitance As the prior condition of MRAS variable model, the MRAS adaptive rule designed in combination with Popov inequality realizes the identification of earth leakage resistance And ground transition resistance The identified earth leakage resistance And ground transition resistance And earth capacitance Are sent into the variable model after the next sampling step, and the iterative optimization of the parameters to be identified is completed through the closed-loop feedback mechanism, finally realizing the collaborative accurate identification of the distribution line earth parameters and ground transition resistance based on RLS-MRAS. The expressions of the ground capacitance, ground leakage resistance and ground transition resistance estimated by the parameter adaptive rule are as follows: wherein and are estimated values of the injected current and the neutral point voltage, and are estimated values of the earth capacitance and the earth leakage resistance.

6. A computer device, comprising: Comprising: A processor, a memory and a bus, the memory storing machine readable instructions executed by the processor; When the computer device is running, the processor communicates with the memory through the bus, and the machine readable instructions are executed by the processor to execute the distribution line-to-ground parameter on-line identification method based on RLS-MRAS as claimed in any one of claims 1 to 5.

7. A computer readable storage medium characterized in that, Comprising: The computer program is stored on the computer readable storage medium; The computer program is executed by the processor to execute the distribution line-to-ground parameter on-line identification method based on RLS-MRAS as claimed in any one of claims 1 to 5.

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