Site selection method and device for active harmonic mitigation of radial distribution networks

Abstract

This invention provides a method and apparatus for selecting the location of an active harmonic mitigation device for radial distribution networks, belonging to the field of power quality management technology. The method includes: acquiring equipment parameters of each branch of the distribution network; determining the harmonic impedance of each branch based on the equipment parameters, and calculating the influence coefficient of each nonlinear load branch's harmonics on the distribution network's harmonic voltage; calculating the contribution rate of each nonlinear load branch's harmonics to the voltage distortion of the distribution network based on the influence coefficients of all nonlinear load branches; determining the numerical distribution characteristics of the voltage distortion contribution rate corresponding to all nonlinear load branches based on the coefficient of variation and a threshold; and determining the optimal location of the active harmonic mitigation device based on the numerical distribution characteristics, the expected minimum target for harmonic mitigation, and the voltage distortion contribution rate corresponding to each nonlinear load branch. This invention can solve the problem of difficult location selection for harmonic mitigation devices in radial distribution networks where harmonic sources are dispersed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of power quality management, and particularly relates to a method for selecting a site of an active management device for a same-level harmonic of a radial distribution network. BACKGROUND

[0002] The flexible and efficient conversion characteristics of power electronics technology meet the needs of the development of various industries in the current society, and are an important basis for promoting the construction of new power systems. The power electronics technology promotes the large-scale grid connection of massive distributed new energy and power electronic equipment, and further causes the rapid rise of the proportion of power electronics in modern distribution networks. However, these devices have significant nonlinearity in the process of energy conversion, which leads to the increasing pollution of harmonics in the distribution network, seriously threatens the safe, stable and efficient operation of the distribution network, and also makes the harmonic sources in the distribution network present new characteristics of decentralization and full-network, which brings great challenges to the site selection of harmonic management devices.

[0003] In fact, in order to ensure the safe operation of the distribution network, the harmonic voltage level (distortion degree) is mainly controlled, and the distortion degree of the grid voltage is determined by the harmonic current emitted by the harmonic source and the harmonic impedance outside. Under the same harmonic current, the greater the harmonic impedance, the higher the contribution rate of voltage distortion, and the higher the management effect and economy of installing a management device at this place. This provides a solution for the site selection of active management devices for the distribution network with multiple-point emission of harmonics. However, with the increase of the cable rate of the distribution line, the distribution network is provided with rich and high-level capacitive parts, which form complex and multi-frequency resonances with inductive parts, change the form of harmonic impedance at different frequencies, and no longer have ideal linear characteristics, resulting in a significant increase in the complexity of the external harmonic impedance of each harmonic source, and the influence of the analysis of the contribution rate of voltage distortion cannot be ignored. SUMMARY

[0004] The embodiments of the present application provide a method and device for selecting a site of an active management device for a same-level harmonic of a radial distribution network, to solve the problem of site selection of harmonic active management devices caused by multiple-point emission of harmonic sources and complex and variable harmonic impedance.

[0005] In a first aspect, the embodiments of the present application provide a method for selecting a site of an active management device for a same-level harmonic of a radial distribution network, comprising:

[0006] Obtaining device parameters of each branch of the distribution network; wherein the distribution network comprises a power supply branch, a reactive compensation branch and a nonlinear load branch;

[0007] Determining the harmonic impedance of each branch according to the device parameters of each branch of the distribution network, and calculating the influence coefficient of each nonlinear load branch on the harmonic voltage of the distribution network, respectively; wherein the device parameters of the nonlinear load branch include the capacitive reactance of the line.

[0008] According to the influence coefficient of all nonlinear load branches, the voltage distortion contribution rate of each nonlinear load branch to the power distribution network is calculated respectively;

[0009] According to the voltage distortion contribution rate corresponding to all nonlinear load branches, the coefficient of variation is calculated, and the numerical distribution characteristics of the voltage distortion contribution rate corresponding to all nonlinear load branches are judged according to the coefficient of variation and the threshold value;

[0010] According to the numerical distribution characteristics, the lowest target expected by the harmonic control, and the voltage distortion contribution rate corresponding to each nonlinear load branch, the optimal site of the harmonic active control device is determined.

[0011] In the second aspect, the embodiment of the present application provides a site selection device of a radial power distribution network harmonic active control device at the same level, which comprises:

[0012] A data acquisition module is configured to acquire equipment parameters of each branch of the power distribution network; wherein the power distribution network comprises a power supply branch, a reactive power compensation branch and a nonlinear load branch;

[0013] An influence coefficient calculation module is configured to determine the harmonic impedance of each branch according to the equipment parameters of each branch of the power distribution network, and calculate the influence coefficient of the harmonic of each nonlinear load branch on the harmonic voltage of the power distribution network respectively; wherein the equipment parameters of the nonlinear load branch include the capacitive reactance of the line;

[0014] A voltage distortion contribution rate calculation module is configured to calculate the voltage distortion contribution rate of the harmonic of each nonlinear load branch to the power distribution network according to the influence coefficient of all nonlinear load branches respectively;

[0015] A numerical distribution characteristic judgment module is configured to calculate the coefficient of variation according to the voltage distortion contribution rate corresponding to all nonlinear load branches, and judge the numerical distribution characteristics of the voltage distortion contribution rate corresponding to all nonlinear load branches according to the coefficient of variation and the threshold value;

[0016] An optimal site determination module is configured to determine the optimal site of the harmonic active control device according to the numerical distribution characteristics, the lowest target expected by the harmonic control, and the voltage distortion contribution rate corresponding to each nonlinear load branch.

[0017] The embodiment of the present application provides a kind of active management device site selection method and device of radial power distribution network same level harmonic, harmonic impedance in nonlinear load branch is calculated by the capacity resistance of power supply line, more accurately assess the voltage distortion contribution rate of harmonic source to power grid, the distribution characteristics of the voltage distortion contribution rate of harmonic in nonlinear load branch, the lowest target of harmonic control expectation and the voltage distortion contribution rate corresponding to each nonlinear load branch determine the site selection strategy of harmonic active management device, reduce the complexity of site selection, reasonably reduce management device, overcome the inefficient problem of excessive number and capacity of management device caused by traditional management scheme. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating labor intensity.

[0019] Figure 1 is the radial power distribution network grid structure and harmonic impedance model schematic diagram of each component device provided by the embodiment of the present application;

[0020] Figure 2 is the implementation flowchart of the active management device site selection method of radial power distribution network same level harmonic provided by the embodiment of the present application;

[0021] Figure 3 is the schematic diagram of voltage distortion contribution rate of each nonlinear load branch to power distribution network provided by the embodiment of the present application;

[0022] Figure 4 is the schematic diagram of voltage distortion contribution rate from large to small arrangement and cumulative result one by one provided by the embodiment of the present application;

[0023] Figure 5 is the structural schematic diagram of the active management device site selection device of radial power distribution network same level harmonic provided by the embodiment of the present application. DETAILED DESCRIPTION

[0024] In the following description, specific details such as specific system structures, techniques, etc. are presented for the purpose of explanation, not for the purpose of limitation, so that the embodiments of the present application can be thoroughly understood. However, it should be clear to those skilled in the art that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed description of well-known systems, devices, circuits and methods is omitted to avoid unnecessary details that hinder the description of the present application.

[0025] In order to make the purpose, technical scheme and advantages of the present application more clear, the following will be described by specific embodiments combined with drawings.

[0026] Figure 1 The radio distribution network framework structure and the harmonic impedance model of each component device provided by the embodiment of the application are shown in the schematic diagram.

[0027] The radio distribution network framework structure comprises branches connected to a bus, and the branches are divided into power supply branches, reactive compensation branches and nonlinear load branches according to attributes. The new energy grid-connected branch is processed as a nonlinear load branch.

[0028] Figure 2 The implementation flowchart of the radio distribution network same-level harmonic active treatment device site selection method provided by the embodiment of the application is shown in FIG. 1. Figure 2 As shown in the figure, the details are as follows.

[0029] Step 101: Obtain the device parameters of each branch of the distribution network; wherein the distribution network comprises power supply branches, reactive compensation branches and nonlinear load branches.

[0030] The power supply branch comprises a power supply and a transformer, the nonlinear load branch comprises a power supply line and a load, and the reactive compensation branch comprises a plurality of reactive compensation groups with different series reactance rates.

[0031] The specific process is as follows:

[0032] (1) Determine whether there is a reactive compensation branch, and count the number of nonlinear load branches.

[0033] (2) Number the nonlinear load branches one by one in the same fixed direction, and recommend increasing the number from left to right.

[0034] (3) Collect the device parameters of the power supply, transformer, power supply line, load and reactive compensation (if any) of the distribution network.

[0035] The power supply parameters include the minimum short-circuit capacity S min , the reactance / resistance ratio X / R, and the rated voltage value U N of the distribution network bus. The transformer parameters include the rated capacity S t , the short-circuit voltage U d , and the short-circuit loss P k . The power supply line parameters include the length of the line l, the unit length resistance R0, the unit length inductance L0, and the unit length capacitance C0. The load parameters include the minimum operating apparent power S d , and the average power factor PF. The reactive compensation parameters include the reactive compensation capacitor bank rated capacity Q co , the capacitor bank rated voltage U C , and the series reactance rate k.

[0036] Step 102: determine the harmonic impedance of each branch according to the equipment parameters of each branch of the power distribution network, and calculate the influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network respectively; wherein the equipment parameters of the nonlinear load branch include the capacitive reactance of the line.

[0037] Considering the influence of resonance on harmonic impedance caused by the increase of capacitive level of the line after the cableization of the power distribution network, the harmonic impedance of each branch is calculated through capacitive reactance, and the voltage distortion contribution rate of the harmonic source to the power grid is more accurately evaluated through harmonic impedance.

[0038] The power supply branch is composed of power supply harmonic impedance and transformer harmonic impedance in series. If there is a reactive compensation branch, if it contains multiple reactive compensation groups with different series reactance rates, the impedance of each reactive compensation group can be calculated first, and then the total harmonic impedance of the reactive compensation branch is calculated. The nonlinear load branch is composed of power supply line harmonic impedance and load harmonic impedance in parallel.

[0039] In a possible implementation, determining the harmonic impedance of each branch according to the equipment parameters of each branch of the power distribution network comprises: respectively determining the harmonic impedance of the power supply branch, the reactive compensation branch and the nonlinear load branch;

[0040] The harmonic impedance of the power supply branch is the sum of the power supply harmonic impedance and the transformer harmonic impedance, and its formula is as follows:

[0041] Z g (h)=Z s (h)+Z t (h)

[0042]

[0043] In the formula, Z s (h) is the power supply harmonic impedance, S min is the minimum short-circuit capacity, X / R is the reactance / resistance ratio, U N is the rated voltage value of the bus of the power distribution network, h is the harmonic number, j is the imaginary symbol in complex number, Z t (h) is the transformer harmonic impedance, S t is the rated capacity, P k is the short-circuit loss, U d is the short-circuit voltage.

[0044] The reactive compensation branch contains multiple reactive compensation groups with different series reactance rates, and the harmonic impedance formula of the reactive compensation branch is as follows:

[0045]

[0046] In the formula, Z co (h) is the reactive compensation impedance, Q co is the rated capacity of the reactive compensation capacitor group, UC is the capacitor bank rated voltage, k is the series reactance rate, e is the different series reactance rate reactive compensation group number, m is the different series reactance rate reactive compensation group quantity, m∈N, h is the harmonic number, h=3,5,7,…,25;

[0047] The nonlinear load branch is composed of the power supply line and the load in series and parallel, and the harmonic impedance formula of the nonlinear load branch is as follows:

[0048]

[0049] Z L (h)=Z0(h)·sinh[γ(h)·l]

[0050]

[0051] In the formula, Z d (h) is the load harmonic impedance, S d is the minimum operating apparent power, PF is the average power factor, Z L (h) is the impedance of the distributed parameter π model of the line, Z0(h) is the characteristic impedance of the line, γ(h) is the line propagation coefficient, l is the length, R0 is the unit length resistance, L0 is the unit length inductance, C0 is the unit length capacitance, ω0 is the fundamental angular frequency, ω0=2πf0, f0=50HZ, Z C (h) is the capacitive reactance of the distributed parameter π model of the line, and h is the harmonic number, h=3,5,7,…,25.

[0052] Normally, the nonlinear load only generates odd harmonics and is mostly within 25 times, so the harmonic number h=3,5,7,…,25.

[0053] In other possible ways, the harmonic impedance of the nonlinear load branch calculated by the capacitive reactance can be calculated in other ways. This application mainly takes the harmonic impedance of the nonlinear load branch calculated by the capacitive reactance as an example for description.

[0054] In one possible implementation, if there is a reactive compensation branch, the total harmonic impedance Z p,i of the other branches except the i-th nonlinear load branch can be calculated as follows:

[0055]

[0056] In the formula, r is the nonlinear load branch number of the distribution network; n is the nonlinear load branch quantity of the distribution network, n∈N.

[0057] In another possible implementation, if there is no reactive compensation branch, the harmonic impedance Z p,iThe formula is as follows:

[0058]

[0059] In the formula, r is the number of the nonlinear load branch of the power distribution network; n is the number of the nonlinear load branch of the power distribution network, n∈N.

[0060] In one possible implementation, the calculation of the influence coefficient of the harmonic of each nonlinear load branch on the harmonic voltage of the power distribution network includes:

[0061] The influence coefficient of the harmonic of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated according to the formula:

[0062]

[0063] The results of the influence coefficient of the harmonic of all nonlinear load branches on the harmonic voltage of the power distribution network are as follows:

[0064]

[0065] In the formula, α i is the influence coefficient of the harmonic generated by the i-th nonlinear load branch on the harmonic voltage of the power distribution network, Z P,i (h) is the total harmonic impedance of other branches except the i-th nonlinear load branch, Z C,i (h) is the capacitive reactance of the distributed parameter π model of the i-th nonlinear load branch, Z L,i (h) is the impedance of the distributed parameter π model of the i-th nonlinear load branch, and n is the number of the nonlinear load branch.

[0066] Step 103: Calculate the voltage distortion contribution rate of the harmonic of each nonlinear load branch on the power distribution network according to the influence coefficient of all nonlinear load branches.

[0067] In the formula, the calculation of the voltage distortion contribution rate of the harmonic of each nonlinear load branch on the power distribution network includes:

[0068] Perform square root operation on the influence coefficient of each harmonic of a nonlinear load branch on the harmonic voltage of the power distribution network.

[0069] Perform proportion operation on the result of the square root operation to obtain the voltage distortion contribution rate of the harmonic of the nonlinear load branch on the power distribution network.

[0070] In actual implementation, the above process needs to be performed on each nonlinear load branch to calculate the voltage distortion contribution rate of the harmonic of all nonlinear load branches on the power distribution network.

[0071] In a possible implementation, the voltage distortion contribution rate of each nonlinear load branch to the power distribution network is calculated according to the influence coefficient of each nonlinear load branch, and the voltage distortion contribution rate of each nonlinear load branch to the power distribution network is calculated according to the influence coefficient of each nonlinear load branch.

[0072] The square root operation is performed on the influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network, and the formula is as follows:

[0073]

[0074] The square root operation result is subjected to the proportion operation to obtain the harmonic voltage distortion contribution rate of each nonlinear load branch to the power distribution network, and the formula is as follows:

[0075]

[0076] In the formula, β i is the square root operation result of the influence coefficient of the i th nonlinear load branch on the harmonic voltage of the power distribution network, λ k is the harmonic voltage distortion contribution rate of the k th nonlinear load branch to the power distribution network, β k is the square root operation result of the influence coefficient of the k th nonlinear load branch on the harmonic voltage of the power distribution network, and n is the number of nonlinear load branches.

[0077] Step 104: Calculate the variation coefficient according to the voltage distortion contribution rates corresponding to all nonlinear load branches, and determine the numerical distribution characteristics of the voltage distortion contribution rates corresponding to all nonlinear load branches according to the variation coefficient and the threshold value.

[0078] The average value and the standard deviation of the voltage distortion contribution rates corresponding to all nonlinear load branches are calculated to obtain the variation coefficient, and the numerical distribution of the voltage distortion contribution rates corresponding to all nonlinear load branches is concentrated distribution or discrete distribution according to the variation coefficient and the threshold value. According to the data distribution characteristics, the corresponding harmonic active treatment device site selection strategy is selected to improve the efficiency of the harmonic active treatment device site selection and reduce the complexity of the method site selection process in a specific scenario.

[0079] In a possible implementation, the variation coefficient is calculated according to the voltage distortion contribution rates corresponding to all nonlinear load branches, and the variation coefficient is calculated according to the average value and the threshold value.

[0080] The average value of the harmonic voltage distortion contribution rates of all nonlinear load branches to the power distribution network is calculated.

[0081] The standard deviation of the harmonic voltage distortion contribution rates of all nonlinear load branches to the power distribution network is calculated according to the average value.

[0082] The standard deviation is divided by the average value to obtain the variation coefficient.

[0083] The calculation formula of the average value is as follows:

[0084]

[0085] In the formula, λ k is the harmonic voltage distortion contribution rate of the kth nonlinear load branch, and n is the number of nonlinear load branches.

[0086] The calculation formula of the standard deviation is as follows:

[0087]

[0088] In the formula, λ k is the harmonic voltage distortion contribution rate of the kth nonlinear load branch, and n is the number of nonlinear load branches.

[0089] The calculation formula of the coefficient of variation is as follows:

[0090]

[0091] In the formula, c is the coefficient of variation.

[0092] The calculation formula of the threshold value is as follows:

[0093]

[0094] In the formula, n is the number of nonlinear load branches; and ε is the maximum relative error allowed in value (%), which is 5%, or other values can be selected according to actual conditions, but should not exceed 10%.

[0095] In a possible implementation, the value distribution characteristics of the voltage distortion contribution rates corresponding to all nonlinear load branches are determined according to the coefficient of variation and the threshold value, and the value distribution characteristics include:

[0096] When the coefficient of variation is greater than the threshold value, the voltage distortion contribution rates corresponding to all nonlinear load branches are in discrete distribution;

[0097] When the coefficient of variation is less than or equal to the threshold value, the voltage distortion contribution rates corresponding to all nonlinear load branches are in concentrated distribution.

[0098] Step 105: According to the value distribution characteristics, the lowest target of harmonic control expectation, and the voltage distortion contribution rates corresponding to each nonlinear load branch, the optimal site of the harmonic active control device is determined.

[0099] The value distribution characteristics of the harmonic source of each nonlinear load branch to the voltage distortion contribution rate are determined, and the corresponding harmonic active control device site selection strategy is determined, so that the complexity of the site selection process under a specific scenario is reduced.

[0100] The nonlinear load branch with high voltage distortion contribution rate is taken as the installation position of the harmonic treatment device, the same capacity harmonic active treatment device is ensured, better treatment effect and economy are achieved, and the problem of excessive number and capacity of treatment devices caused by installing treatment devices in the whole distribution network for treating multiple point harmonic sources is reduced.

[0101] The embodiment of the application provides a kind of active treatment device site selection method and device for radial distribution network harmonic of the same level, the harmonic impedance in the nonlinear load branch is calculated by the capacity of supply line, the voltage distortion contribution rate of harmonic source to power grid is more accurately evaluated, the site selection strategy of harmonic active treatment device is determined by the distribution characteristics of the voltage distortion contribution rate of nonlinear load branch, the minimum target of harmonic treatment expectation and the voltage distortion contribution rate corresponding to each nonlinear load branch, the complexity of site selection is reduced, and the treatment device is reasonably reduced, to overcome the inefficient problem of excessive number and capacity of treatment devices caused by traditional treatment scheme.

[0102] In a possible implementation manner, according to the numerical distribution characteristics, the minimum target of harmonic treatment expectation and the voltage distortion contribution rate corresponding to each nonlinear load branch, the best site selection of harmonic active treatment device includes:

[0103] When the voltage distortion contribution rate is concentrated distribution, the minimum target value is divided by the average value of the voltage distortion contribution rate corresponding to all nonlinear load branches, to obtain a ratio result;

[0104] According to the ratio result, a corresponding number of nonlinear load branches are randomly selected from all nonlinear load branches, to determine the installation position of harmonic active treatment device;

[0105] When the voltage distortion contribution rate is discrete distribution, the voltage distortion contribution rates corresponding to all nonlinear load branches are arranged in descending order;

[0106] The voltage distortion contribution rates after arrangement are added one by one;

[0107] When the added result first meets the judgment condition, the nonlinear load branch corresponding to the added voltage distortion contribution rate is determined as the installation position of harmonic active treatment device.

[0108] In a possible implementation manner, when the voltage distortion contribution rate corresponding to nonlinear load branch is concentrated distribution, the site selection of harmonic active treatment device is carried out according to the following strategy:

[0109] a) According to the ratio of the value of the minimum target of treatment expectation to the average value of voltage distortion contribution rate, the number N of branches needing to install harmonic active treatment device is determined t :

[0110]

[0111] In the formula, G is the minimum target.

[0112] b) Optionally selecting N t The nonlinear load branch is installed as a harmonic active management device installation location, and the site selection work is completed.

[0113] In another possible implementation, when the voltage distortion contribution rate corresponding to the nonlinear load branch is a discrete distribution, the site selection of the harmonic management device is performed according to the following strategy.

[0114] The voltage distortion contribution rates corresponding to all nonlinear load branches are arranged in descending order, and the result is shown in the following formula:

[0115] B = [λ (1) , λ (2) , λ (3) , …, λ (n) ]

[0116] In the formula, the superscripts (1), (2), …, (n) represent the positions of the voltage distortion contribution rates corresponding to the n nonlinear load branches arranged in descending order.

[0117] The arranged voltage distortion contribution rates are added one by one according to the following formula:

[0118]

[0119] In the formula, x represents the voltage distortion contribution rate at the xth position after sorting; M y y represents the yth addition result, which is added by the y voltage distortion contribution rates arranged at this time, y = 1, 2, …, n, when y is 1, the addition result is the maximum value of the voltage distortion contribution rate, that is, M1 = λ (1) .

[0120] It is judged whether the result M y of each addition satisfies the condition of being greater than or equal to the minimum target G of harmonic management, and the formula is as follows:

[0121] M y ≥ G

[0122] In the formula, M y is the result of each addition, and G is the minimum target.

[0123] When the judgment condition is satisfied for the first time, the nonlinear load branch corresponding to the added voltage distortion contribution rate is installed as the harmonic active management device installation location, and the load branch with a higher voltage distortion contribution rate is preferentially installed with the harmonic active management device, and the site selection work is completed.

[0124] In one possible implementation, the determination of the minimum target of harmonic management includes:

[0125] obtaining the distortion improvement rate of the power distribution network voltage;

[0126] obtaining the compensation rate of the harmonic active treatment device;

[0127] dividing the distortion improvement rate by the compensation rate of the harmonic active treatment device, and the ratio obtained is the lowest target of the harmonic treatment expectation.

[0128] The voltage distortion improvement rate of the power distribution network can be determined in the following manner:

[0129] For the power distribution network whose total harmonic voltage distortion rate (THDu) exceeds the limit value specified in GB / T 14549, the minimum improvement rate can be determined according to the 95% probability maximum value THDu1 of the total harmonic voltage distortion rate of the actual operation of the power distribution network and the limit value THDu2, according to the following formula:

[0130]

[0131] The expected total harmonic voltage distortion rate THDu3 of the power distribution network after harmonic treatment is artificially set, and then combined with the 95% probability maximum value THDu1 of the total harmonic voltage distortion rate of the actual operation of the power distribution network, the minimum improvement rate is determined according to the following formula:

[0132]

[0133] When the harmonic treatment device is actually operated, it is affected by the detection, control and other links, and the compensation rate η of the harmonic treatment device b cannot reach the ideal 100%, and the actual compensation rate η of each harmonic of the device b can be obtained in the following two ways:

[0134] a) It can be obtained through the third-party detection report of the manufacturer on the performance of the harmonic treatment device;

[0135] b) When the detection report cannot be obtained, the harmonic compensation rate limit value specified in the relevant national standard of the harmonic treatment device can be consulted, and this value is taken as the harmonic treatment device compensation rate of the method.

[0136] Given the power distribution network voltage distortion improvement rate and the harmonic treatment device compensation rate, the value of the lowest target of the power distribution network harmonic treatment expectation can be calculated in the following formula:

[0137]

[0138] In the formula, G is the lowest target.

[0139] Considering the actual compensation rate of the harmonic active treatment device cannot reach 100%, in combination with the voltage distortion improvement rate of the distribution network, the lowest target of the expected harmonic treatment of the distribution network is determined to ensure that the harmonic active treatment reaches the expected treatment effect.

[0140] In a possible implementation, the judgment condition is:

[0141] The accumulated result is greater than or equal to the lowest target of the expected harmonic treatment.

[0142] In order to better understand the present application, the above process is described in detail below in combination with a specific example. The numerical values used in the example are only for illustration, and the user can make corresponding changes according to actual needs. The example is a radial distribution network of 35kV voltage level. The distribution network has 1 power supply branch, 8 nonlinear load branches, and no reactive power compensation branch. The power supply branch composition equipment parameters are shown in Table 1, and the nonlinear load branch composition equipment parameters are shown in Table 2.

[0143] Table 1 Power supply branch composition equipment parameters

[0144]

[0145] Table 2 Nonlinear load branch composition equipment parameters

[0146]

[0147] In combination with the composition equipment parameters of the distribution network, the harmonic impedance of each branch of the distribution network is calculated according to step 102. On this basis, the influence coefficient of each of the 8 nonlinear load branches on the odd harmonic voltage of the distribution network within 25 times is calculated, and the results are shown in Table 3.

[0148] Table 3 Calculation results of the influence coefficient of each nonlinear load branch on the harmonic voltage of the distribution network

[0149]

[0150]

[0151] Then, according to step 103, the influence coefficients of the 8 nonlinear load branches on the harmonic voltage of the distribution network in Table 3 are processed by sum and root, and their proportions are calculated to finally obtain the harmonic voltage distortion contribution rate of each nonlinear load branch, and the results are shown in Table 5. Figure 3 According to the requirements of step 104, the average value μ and the standard deviation σ of the voltage distortion contribution rate are calculated respectively, and the coefficient of variation c is solved. Since the number of nonlinear load branches n is 8, the maximum allowable relative error ε is set to 5%, and the threshold value can be calculated, and the results are shown in Table 4. Since the coefficient of variation is greater than the threshold value, it can be judged that it is a discrete distribution.

[0152] Table 4 voltage distortion contribution rate numerical distribution characteristic judgment parameter calculation result

[0153] Object Calculated value Mean μ 12.5 Standard deviation σ 3.33 Coefficient of variation c 0.267 Threshold value T 0.022

[0154] Set the power distribution network voltage distortion improvement rate η a 50%, the compensation rate η of the selected harmonic control device b 85%, the calculated minimum target G of the harmonic control is 58.82%. Under the above results, according to step 105, the harmonic contribution rate of each nonlinear load branch to the power distribution network voltage distortion is arranged from large to small, and the results are shown in Table 5.

[0155] Table 5 voltage distortion contribution rate arranged from large to small

[0156]

[0157]

[0158] The arranged voltage distortion contribution rate is added one by one, as shown in Figure 4 When the addition is added to the fourth time, the addition result M4=58.95%, which exceeds the value of the minimum target of the harmonic control for the first time, so the harmonic active control device needs to be installed on the nonlinear load branches numbered 8, 6, 5 and 3, and the active device site selection of the harmonic control of the radial power distribution network is completed.

[0159] The present application provides a kind of active harmonic control device site selection method and device of radial power distribution network, solve the problem of harmonic active control device site selection caused by multiple point emission of harmonic source and complex and changeable harmonic impedance, both reduce the installation quantity of whole distribution network control device, also ensure the voltage distortion control effect and economy of power distribution network, finally support the high quality and high reliability operation of power distribution network.

[0160] The present application considers that the line capacity level is improved after the cable of power distribution network, and the influence of resonance on harmonic impedance, more accurately assesses the voltage distortion contribution rate of harmonic source to power grid through harmonic impedance;The distribution characteristics of the voltage distortion contribution rate of each harmonic source are determined to determine the harmonic active control device site selection strategy, which reduces the complexity of the method site selection process in a specific scenario;Considering that the actual compensation rate of harmonic active control device cannot reach 100%, combined with the voltage distortion improvement rate of power distribution network, the minimum target of the expected harmonic control of power distribution network is determined to ensure that the harmonic active control reaches the expected control effect;The nonlinear load branch with high voltage distortion contribution rate is selected as the preferred harmonic control device installation position, which ensures that the same capacity harmonic active control device can achieve better control effect and economy, reduces the installation of control device in whole power distribution network when multiple point emission harmonic source is controlled, and solves the problem of excessive number and capacity of device.

[0161] It should be understood that the size of the serial number of each step in the above embodiment does not mean the order of execution, and the execution order of each process should be determined according to its function and inherent logic, and should not constitute any limitation on the implementation process of the embodiment of the application.

[0162] The following is the device embodiment of the application, and for the details not described in detail, reference can be made to the corresponding method embodiments described above.

[0163] Figure 5 The structural schematic diagram of the active management device site selection device for the radial power distribution network is shown, only the part related to the embodiment of the application is shown for the convenience of description, and the details are as follows:

[0164] As shown in Figure 5 The active management device site selection device 5 for the radial power distribution network includes

[0165] The data acquisition module 51 is configured to acquire the equipment parameters of each branch of the power distribution network; wherein, the power distribution network includes the power supply branch, the reactive power compensation branch and the nonlinear load branch;

[0166] The influence coefficient calculation module 52 is configured to determine the harmonic impedance of each branch according to the equipment parameters of each branch of the power distribution network, and calculate the influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network respectively; wherein, the equipment parameters of the nonlinear load branch include the capacitive reactance of the line;

[0167] The voltage distortion contribution rate calculation module 53 is configured to calculate the voltage distortion contribution rate of each nonlinear load branch on the power distribution network according to the influence coefficient of all nonlinear load branches respectively;

[0168] The numerical distribution characteristic judgment module 54 is configured to calculate the coefficient of variation according to the voltage distortion contribution rate corresponding to all nonlinear load branches, and judge the numerical distribution characteristic of the voltage distortion contribution rate corresponding to all nonlinear load branches according to the coefficient of variation and the threshold value;

[0169] The optimal site determination module 55 is configured to determine the optimal site of the harmonic active management device according to the numerical distribution characteristic, the lowest target of the harmonic management expectation and the voltage distortion contribution rate corresponding to each nonlinear load branch.

[0170] In a possible implementation manner, the numerical distribution characteristic judgment module 54 is configured to:

[0171] The calculation of the coefficient of variation according to the voltage distortion contribution rate corresponding to all nonlinear load branches includes:

[0172] Calculate the average value of the voltage distortion contribution rate of the harmonic of all nonlinear load branches on the power distribution network;

[0173] The standard deviation of the harmonic voltage distortion contribution rate of all nonlinear load branches is calculated according to the average value.

[0174] The ratio obtained by dividing the standard deviation by the average value is the coefficient of variation.

[0175] In a possible implementation, the numerical distribution feature determination module 54 is configured to:

[0176] The numerical distribution feature of the voltage distortion contribution rate corresponding to all nonlinear load branches is determined according to the coefficient of variation and the threshold value, and includes:

[0177] When the coefficient of variation is greater than the threshold value, the voltage distortion contribution rate corresponding to all nonlinear load branches is discrete distribution;

[0178] When the coefficient of variation is less than or equal to the threshold value, the voltage distortion contribution rate corresponding to all nonlinear load branches is concentrated distribution.

[0179] The embodiment of the present application provides a kind of active management device site selection method and device of radial distribution network harmonic, the harmonic impedance in nonlinear load branch is calculated by the reactance of power supply line, more accurately assesses the voltage distortion contribution rate of harmonic source to power grid, the distribution feature of the voltage distortion contribution rate of nonlinear load branch, the lowest target of harmonic management expectation and the voltage distortion contribution rate corresponding to each nonlinear load branch are determined to select the site strategy of harmonic active management device, reduce the complexity of site selection, reasonably reduce management device, overcome the inefficient problem of excessive management device quantity and capacity caused by traditional management scheme.

[0180] In the above embodiment, the description of each embodiment has its own emphasis, and the parts not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0181] Those skilled in the art can realize that the templates, units and algorithm steps of each example described in combination with the embodiments disclosed herein can be realized by electronic hardware or a combination of computer software and electronic hardware. Whether the functions are realized in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to realize the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0182] If the modules are implemented in the form of software function units and sold or used as independent products, they can be stored in a computer readable storage medium. Based on this understanding, all or part of the processes in the above-mentioned embodiment methods can also be completed by a computer program instructing related hardware, and the computer program can be stored in a computer readable storage medium. When the computer program is executed by a processor, the steps of the above-mentioned various radial distribution network harmonic active treatment device site selection method embodiments can be implemented. The computer program includes computer program code, which can be in the form of source code, object code, executable files or some intermediate forms, etc. The computer readable medium can include any entity or device capable of carrying computer program code, recording medium, U disk, mobile hard disk, magnetic disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium, etc.

[0183] The above embodiments are only used to illustrate the technical solutions of the present application, but not limit it; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A method for selecting a location for an active harmonic mitigation device in a radial power distribution network, characterized in that, The method comprises the following steps: obtaining device parameters of each branch of a power distribution network; wherein the power distribution network comprises a power supply branch, a reactive power compensation branch and a nonlinear load branch; determining the harmonic impedance of each branch according to the device parameters of each branch of the power distribution network, and respectively calculating the influence coefficient of the harmonic of each nonlinear load branch on the harmonic voltage of the power distribution network; wherein the device parameters of the nonlinear load branch include the capacitive reactance of the line; respectively calculating the voltage distortion contribution rate of the harmonic of each nonlinear load branch to the power distribution network according to the influence coefficient of all nonlinear load branches; calculating the coefficient of variation according to the voltage distortion contribution rate corresponding to all nonlinear load branches, judging the numerical distribution characteristics of the voltage distortion contribution rate corresponding to all nonlinear load branches according to the coefficient of variation and a threshold value; determining the optimal location of the harmonic active control device according to the numerical distribution characteristics, the lowest target of harmonic control expectation and the voltage distortion contribution rate corresponding to each nonlinear load branch.

2. The method of claim 1, wherein the method further comprises: The calculation of the coefficient of variation according to the voltage distortion contribution rate corresponding to all nonlinear load branches comprises: calculating the average value of the voltage distortion contribution rate of the harmonic of all nonlinear load branches to the power distribution network; calculating the standard deviation of the voltage distortion contribution rate of the harmonic of all nonlinear load branches to the power distribution network according to the average value; dividing the standard deviation by the average value to obtain the coefficient of variation.

3. The method of claim 2, wherein the method further comprises: The judgment of the numerical distribution characteristics of the voltage distortion contribution rate corresponding to all nonlinear load branches according to the coefficient of variation and the threshold value comprises: when the coefficient of variation is greater than the threshold value, the voltage distortion contribution rate corresponding to all nonlinear load branches is discrete distribution; when the coefficient of variation is less than or equal to the threshold value, the voltage distortion contribution rate corresponding to all nonlinear load branches is concentrated distribution.

4. The method of claim 3, wherein the method further comprises: The determination of the optimal location of the harmonic active control device according to the numerical distribution characteristics, the lowest target of harmonic control expectation and the voltage distortion contribution rate corresponding to each nonlinear load branch comprises: when the voltage distortion contribution rate is concentrated distribution, dividing the numerical value of the lowest target by the average value of the voltage distortion contribution rate corresponding to all nonlinear load branches to obtain a ratio result; selecting a corresponding number of nonlinear load branches from all nonlinear load branches according to the ratio result to determine the installation position of the harmonic active control device; when the voltage distortion contribution rate is discrete distribution, arranging the voltage distortion contribution rate corresponding to all nonlinear load branches in descending order; adding the voltage distortion contribution rate one by one after arrangement; when the cumulative result first meets the judgment condition, the nonlinear load branch corresponding to the cumulative voltage distortion contribution rate is determined as the installation position of the harmonic active control device.

5. The method of claim 4, wherein, The determination of the lowest target of harmonic control expectation comprises: obtaining the distortion improvement rate of the voltage of the power distribution network; obtaining the compensation rate of the harmonic active control device; dividing the distortion improvement rate by the compensation rate of the harmonic active control device to obtain the ratio result as the lowest target of harmonic control expectation.

6. The method of claim 4, wherein the method further comprises: The judgment condition is: the cumulative result is greater than or equal to the lowest target of harmonic control expectation.

7. The method of claim 1, wherein the method further comprises: The harmonic impedance of each branch is determined according to the equipment parameters of each branch of the power distribution network, including: the harmonic impedance of the power supply branch, the reactive compensation branch and the nonlinear load branch is determined respectively; The harmonic impedance of the power supply branch is the sum of the power supply harmonic impedance and the transformer harmonic impedance, and the formula is as follows: Z g (h) = Z s (h) + Z t (h) where Z s (h) is the power supply harmonic impedance, S min is the minimum short circuit capacity, X / R is the reactance / resistance ratio, U N is the distribution network busbar rated voltage value, h is the harmonic number, j is the imaginary symbol in complex number, Z t (h) is the transformer harmonic impedance, S t is the rated capacity, P k is the short circuit loss, U d is the short circuit voltage; The reactive compensation branch includes multiple reactive compensation groups with different series reactance rates, and the harmonic impedance formula of the reactive compensation branch is as follows: wherein Z co (h) is the reactive compensation impedance, Q co is the reactive compensation capacitor bank rated capacity, U C is the capacitor bank rated voltage, k is the series reactance rate, e is the number of different series reactance rate reactive compensation groups, m is the number of different series reactance rate reactive compensation groups, m ∈ N; The nonlinear load branch is composed of power supply lines and load series-parallel connection, and the harmonic impedance formula of the nonlinear load branch is as follows: Z L (h) = Z0(h) - sinh [γ(h) - l] where Z d (h) is the load harmonic impedance, S d is the load minimum operating apparent power, PF is the load average power factor, Z L (h) is the impedance of the distributed parameter π model of the line, Z0(h) is the line characteristic impedance, γ(h) is the line propagation coefficient, l is the length, R0 is the unit length resistance, L0 is the unit length inductance, C0 is the unit length capacitance, ω0 is the fundamental angular frequency, ω0 = 2πf0, f0 = 50 HZ, Z C (h) is the capacitive reactance of the distributed parameter π model of the line, h is the harmonic number, h = 3, 5, 7, …, 25, sinh is the hyperbolic sine function, cosh is the hyperbolic cosine function.

8. The method of claim 7, wherein the method further comprises: The harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated, and the formula is as follows: The harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated, and the formula is as follows: The harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated, and the formula is as follows: wherein α i is the harmonic voltage influence coefficient of the i-th nonlinear load branch on the distribution network, Z p,i (h) is the total harmonic impedance of other branches other than the i-th nonlinear load branch, Z C,i (h) is the capacitive reactance of the distributed parameter π model for the i-th nonlinear load branch, Z L,i (h) is the impedance of the distributed parameter π model for the i-th nonlinear load branch.

9. The method of claim 8, wherein, The harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated, and the formula is as follows: The harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated, and the formula is as follows: The harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated, and the formula is as follows: wherein β i is the square root of the sum of the influence coefficients of the i-th non-linear load branch on the harmonic voltage of the distribution network, λ k is the contribution rate of the harmonic generated by the k-th non-linear load branch to the voltage distortion of the distribution network, β k is the square root of the sum of the influence coefficients of the k-th non-linear load branch on the harmonic voltage of the distribution network, and n is the number of non-linear load branches.

10. A device for locating an active device for the management of radial power distribution network homologous harmonics, characterized in that it comprises: The harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated, and the formula is as follows: The harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network is calculated, and the formula is as follows: The data acquisition module is used to acquire the equipment parameters of each branch of the power distribution network; wherein, the power distribution network includes power supply branch, reactive compensation branch and nonlinear load branch; The influence coefficient calculation module is used to determine the harmonic impedance of each branch according to the equipment parameters of each branch of the power distribution network, and to calculate the harmonic influence coefficient of each nonlinear load branch on the harmonic voltage of the power distribution network; wherein, the equipment parameters of the nonlinear load branch include capacitive reactance; The voltage distortion contribution rate calculation module is used to calculate the voltage distortion contribution rate of each nonlinear load branch on the power distribution network according to the influence coefficient of all nonlinear load branches; The numerical distribution characteristic judgment module is used to calculate the coefficient of variation according to the voltage distortion contribution rate corresponding to all nonlinear load branches, and to judge the numerical distribution characteristic of the voltage distortion contribution rate corresponding to all nonlinear load branches according to the coefficient of variation and the threshold value; The optimal site determination module is used to determine the optimal site of the harmonic active control device according to the numerical distribution characteristic, the lowest target of harmonic control expectation and the voltage distortion contribution rate corresponding to each nonlinear load branch.

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