CN113452005B - Urban power grid transformer direct-current magnetic bias suppression method - Google Patents

Urban power grid transformer direct-current magnetic bias suppression method Download PDF

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CN113452005B
CN113452005B CN202110727846.5A CN202110727846A CN113452005B CN 113452005 B CN113452005 B CN 113452005B CN 202110727846 A CN202110727846 A CN 202110727846A CN 113452005 B CN113452005 B CN 113452005B
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林圣�
王爱民
周奇
何正友
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Southwest Jiaotong University
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
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    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H7/00—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions
    • H02H7/04—Emergency protective circuit arrangements specially adapted for specific types of electric machines or apparatus or for sectionalised protection of cable or line systems, and effecting automatic switching in the event of an undesired change from normal working conditions for transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
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Abstract

The invention discloses a method for restraining direct current magnetic bias of an urban power grid transformer. The method specifically comprises the following steps: the method comprises the steps of establishing a direct-current resistance network model of the subway and the urban power grid based on a topological structure of the subway and the urban power grid, calculating main transformer neutral point current by using a node admittance method, using the condition that the amplitude of the main transformer neutral point current exceeds a threshold value as a constraint condition, adopting a capacitance blocking device to inhibit the main transformer neutral point current, establishing a target function by taking the minimum installation number of the blocking device as a target under the condition that the main transformer neutral point direct current meets the direct-current magnetic bias inhibition requirement, and optimizing the installation position of the capacitance blocking device through a genetic algorithm. According to the scheme, according to the topological and electrical connection relation between a subway and an urban power grid, the distribution of direct current in the power grid after the capacitor blocking devices are installed is considered, the optimized suppression of the direct current magnetic bias of the transformer aiming at the urban power grid area is realized, the number of the capacitor blocking devices is reduced, and the main transformer direct current magnetic bias suppression cost is saved.

Description

Urban power grid transformer direct-current magnetic bias suppression method
Technical Field
The invention belongs to the field of safe operation of power systems, and particularly relates to a method for restraining direct current magnetic bias of a transformer of an urban power grid.
Background
Because the rail is not completely insulated from ground, the return current in the rail leaks out of the rail to form stray currents. Leaked subway stray current enters an urban power grid to cause the phenomenon of main transformer direct current magnetic biasing. At present, a plurality of urban power grids such as Beijing, Guangzhou, Shenzhen, Changsha and the like have main transformer direct current magnetic biasing phenomena, so that main transformer vibration is aggravated, abnormal sound is increased, harmonic content is increased, local temperature rise is increased, main transformer insulation parts are vibrated to fall off, winding burning loss, protection misoperation and the like are caused in serious cases, and safe and stable operation of the urban power grids is seriously influenced.
At present, the main transformer direct current magnetic bias suppression of the urban power grid mainly adopts an out-of-limit immediate-switching strategy, namely, a main transformer neutral point direct current is switched into a DC blocking device after exceeding a threshold value. Due to the fact that topology of an urban power grid is complex and complex electrical connection paths exist among substations, when a suppression strategy is applied to a direct-current magnetic bias main transformer, the phenomenon that direct current of a neutral point of a transformer, which is not subjected to direct-current magnetic bias, exceeds a limit and direct-current magnetic bias occurs nearby is caused. In order to realize comprehensive main transformer direct current magnetic bias inhibition, experts conduct research on the optimization inhibition of main transformer direct current magnetic bias caused by direct current grounding electrode grounding current, and realize the comprehensive inhibition of main transformer direct current magnetic bias of a power grid through optimizing a DC blocking installation position. However, unlike the direct current grounding electrode grounding current with a fixed position and a determined amplitude, the distribution of the subway stray current has the characteristic of random fluctuation, so the existing main transformer direct current magnetic bias suppression strategy for the direct current grounding electrode cannot be completely suitable for the comprehensive suppression of the main transformer direct current magnetic bias of the urban power grid.
Disclosure of Invention
Aiming at the problems, the invention provides a method for restraining the direct current magnetic bias of the transformer of the urban power grid.
The invention discloses a method for restraining direct current magnetic bias of an urban power grid transformer, which comprises the following steps of:
step 1: and establishing a direct-current resistance network model of the subway and the urban power grid, and calculating the current of a main transformer neutral point.
Step 2: obtaining a direct current magnetic bias current limit value of a main transformer of the urban power grid, initializing the installation position of a capacitance blocking device, and calculating the current of a neutral point of the main transformer of the urban power grid after the capacitance blocking device is installed.
And step 3: and establishing a main transformer direct-current magnetic biasing optimization suppression objective function and constraint conditions according to the main transformer neutral point current and the installation number of the DC blocking devices.
And 4, step 4: and optimizing the installation position of the DC blocking device based on a genetic algorithm to realize the DC magnetic bias suppression of the main transformer.
Further, step 1 specifically comprises:
s11: the method comprises the steps of obtaining related electrical parameters of a subway line topology, a traction power supply system and a reflux system, obtaining direct-current resistance parameters of a winding of a transformer of an urban power grid, transmission lines/cables and the like, and obtaining the number N of neutral point grounding main transformers.
S12: and establishing a direct current resistance network model of the subway and the urban power grid according to the topological structure and the electrical connection relation of the subway and the urban power grid, and assigning direct current resistance in the model.
S13: obtaining train position and traction current, assigning a value to model excitation, calculating node voltage of a direct current resistance network by using a node admittance method, and calculating neutral point current I ═ I of each transformer according to the node voltage and direct current resistance of a transformer winding1,I2,I3,…,IN]。
Further, step 2 specifically comprises:
s21: obtaining main transformer neutral point direct current limit value I of urban power gridthIf the absolute value of the neutral point direct current of the main transformer is larger than IthAnd S22 is entered, if the absolute value of the main transformer neutral point direct current is less than IthThe train position and the traction current are updated, and the process returns to step S13.
S22: the number of the initialized population is 100, and each chromosome matrix M1,M2,…,Mi,…,M100The length is N, the chromosome matrix value is random binary data, each group of matrixes corresponds to a capacitor blocking installation strategy, and the matrix M isi(j) The number f of the capacitor blocking devices is 1, and the blocking devices are installed at the neutral points of the main transformers of the jth transformeriIs MiNumber of 1 in matrix:
fi＝∑Mi
s23: the equivalent direct current resistance of the capacitance blocking device is 105Ω, calculating M according to step S13iThe current of the neutral point of the main transformer is obtained after the corresponding capacitive DC blocking devices are installed, and the maximum amplitude J of the current of the neutral point of the main transformer corresponding to each group of capacitive DC blocking device strategies is counted1,J2,…,Ji,…,J100。
Further, step 3 specifically comprises:
s31: the main transformer direct current magnetic biasing optimization suppression target is as follows:
Figure BDA0003138183240000021
s32: the DC constraint conditions of the variable neutral point in the optimization inhibition process are as follows:
Ji≤Ith
further, step 4 specifically includes:
s41: calculating the target function value of H after each group of capacitance blocking device installation strategies are applied according to the capacitance blocking device installation strategies corresponding to 100 groups of chromosomes1,H2,…,Hi,…,H100。
S42: the installation position of the capacitance blocking device is optimized based on a genetic algorithm, a roulette selection method of random traversal sampling is adopted, the population cross probability is 0.6, the gene variation probability is 0.2, and the iteration number is 200.
S43: after iteration is terminated, the chromosome corresponding to the minimum target result meeting the constraint condition is an optimal inhibition strategy, and 1 in the chromosome is the installation position of the capacitance blocking device.
The beneficial technical effects of the invention are as follows:
firstly, establishing a direct-current resistance network model of a subway and an urban power grid based on an actual subway line structure, a train running position and traction current distribution, and realizing direct-current calculation of a main transformer neutral point.
And secondly, by reasonably setting constraint conditions and optimizing targets, the evaluation of the direct current magnetic biasing of the main transformer of the urban power grid is realized.
And thirdly, based on a genetic algorithm, the optimization of the installation position of the urban power grid capacitance blocking device is realized, and the cost is saved for the suppression of the direct current magnetic bias in the overall colleges.
Drawings
Fig. 1 is a flow chart of the method for suppressing dc magnetic bias of the transformer of the urban power grid.
Detailed Description
The invention is described in further detail below with reference to the figures and the detailed description.
The flow chart of the method for suppressing the direct current magnetic bias of the transformer of the urban power grid is shown in fig. 1, and specifically comprises the following steps:
step 1: and establishing a direct-current resistance network model of the subway and the urban power grid, and calculating the current of a main transformer neutral point.
S11: the method comprises the steps of obtaining related electrical parameters of a subway line topology, a traction power supply system and a reflux system, obtaining direct-current resistance parameters of a winding of a transformer of an urban power grid, transmission lines/cables and the like, and obtaining the number N of neutral point grounding main transformers.
S12: and establishing a direct current resistance network model of the subway and the urban power grid according to the topological structure and the electrical connection relation of the subway and the urban power grid, and assigning direct current resistance in the model.
S13: obtaining train position and traction current, assigning a value to model excitation, calculating node voltage of a direct current resistance network by using a node admittance method, and calculating neutral point current I ═ I of each transformer according to the node voltage and direct current resistance of a transformer winding1,I2,I3,…,IN]。
Step 2: obtaining a direct current magnetic bias current limit value of a main transformer of the urban power grid, initializing the installation position of a capacitance blocking device, and calculating the current of a neutral point of the main transformer of the urban power grid after the capacitance blocking device is installed.
S21: obtaining main transformer neutral point direct current limit value I of urban power gridthIf the absolute value of the neutral point direct current of the main transformer is larger than IthAnd S22 is entered, if the absolute value of the main transformer neutral point direct current is less than IthThe train position and the traction current are updated, and the process returns to step S13.
S22: the number of the initialized population is 100, and each chromosome matrix M1,M2,…,Mi,…,M100The length is N, the chromosome matrix value is random binary data, each group of matrixes corresponds to a capacitor blocking installation strategy, and the matrix M isi(j) The number f of the capacitor blocking devices is 1, and the blocking devices are installed at the neutral points of the main transformers of the jth transformeriIs MiNumber of 1 in matrix:
fi＝∑Mi
s23: the equivalent direct current resistance of the capacitance blocking device is 105Ω, calculating M according to step S13iThe current of the neutral point of the main transformer is obtained after the corresponding capacitive DC blocking devices are installed, and the maximum amplitude J of the current of the neutral point of the main transformer corresponding to each group of capacitive DC blocking device strategies is counted1,J2,…,Ji,…,J100。
And step 3: and establishing a main transformer direct-current magnetic biasing optimization suppression objective function and constraint conditions according to the main transformer neutral point current and the installation number of the DC blocking devices.
S31: the main transformer direct current magnetic biasing optimization suppression target is as follows:
Figure BDA0003138183240000031
s32: the DC constraint conditions of the variable neutral point in the optimization inhibition process are as follows:
Ji≤Ith
and 4, step 4: and optimizing the installation position of the DC blocking device based on a genetic algorithm to realize the DC magnetic bias suppression of the main transformer.
S41: calculating the target function value of H after each group of capacitance blocking device installation strategies are applied according to the capacitance blocking device installation strategies corresponding to 100 groups of chromosomes1,H2,…,Hi,…,H100。
S42: the installation position of the capacitance blocking device is optimized based on a genetic algorithm, a roulette selection method of random traversal sampling is adopted, the population cross probability is 0.6, the gene variation probability is 0.2, and the iteration number is 200.
S43: after iteration is terminated, the chromosome corresponding to the minimum target result meeting the constraint condition is an optimal inhibition strategy, and 1 in the chromosome is the installation position of the capacitance blocking device.

Claims (1)

1. A method for restraining direct current magnetic bias of an urban power grid transformer is characterized by comprising the following steps:
step 1: establishing a direct-current resistance network model of a subway and an urban power grid, and calculating the current of a main transformer neutral point;
s11: acquiring related electrical parameters of a subway line topology, a traction power supply system and a reflux system, acquiring direct-current resistance parameters of a winding of a transformer of an urban power grid, transmission lines/cables and the like, and the number N of neutral point grounding main transformers;
s12: establishing a direct current resistance network model of the subway and the urban power grid according to the topological structure and the electrical connection relation of the subway and the urban power grid, and assigning direct current resistance in the model;
s13: obtaining train position and traction current, assigning a value to model excitation, calculating node voltage of a direct current resistance network by using a node admittance method, and calculating neutral point current I ═ I of each transformer according to the node voltage and direct current resistance of a transformer winding1,I2,I3,…,IN]；
Step 2: acquiring a direct current magnetic bias current limit value of a main transformer of the urban power grid, initializing the installation position of a capacitance blocking device, and calculating the current of a neutral point of the main transformer of the urban power grid after the capacitance blocking device is installed;
s21: obtaining main transformer neutral point direct current limit value I of urban power gridthIf the absolute value of the neutral point direct current of the main transformer is larger than IthAnd S22 is entered, if the absolute value of the main transformer neutral point direct current is less than IthUpdating the train position and the traction current, and returning to the step S13;
s22: the number of the initialized population is 100, and each chromosome matrix M1,M2,…,Mi,…,M100The length is N, the chromosome matrix value is random binary data, each group of matrixes corresponds to a capacitor blocking installation strategy, and the matrix M isi(j) The number f of the capacitor blocking devices is 1, and the blocking devices are installed at the neutral points of the main transformers of the jth transformeriIs MiNumber of 1 in matrix:
fi＝∑Mi
s23: the equivalent direct current resistance of the capacitance blocking device is 105Ω, calculating M according to step S13iThe current of the neutral point of the main transformer is obtained after the corresponding capacitive DC blocking devices are installed, and the maximum amplitude J of the current of the neutral point of the main transformer corresponding to each group of capacitive DC blocking device strategies is counted1,J2,…,Ji,…,J100；
And step 3: establishing a main transformer direct-current magnetic biasing optimization suppression objective function and constraint conditions according to the main transformer neutral point current and the installation number of the DC blocking devices;
s31: the optimized suppression target of the main transformer direct current magnetic biasing H is as follows:
Figure FDA0003564366910000011
s32: the DC constraint conditions of the variable neutral point in the optimization inhibition process are as follows:
Ji≤Ith
and 4, step 4: optimizing the installation position of the DC blocking device based on a genetic algorithm to realize the DC magnetic bias suppression of the main transformer;
s41: calculating the target function value of H after each group of capacitance blocking device installation strategies are applied according to the capacitance blocking device installation strategies corresponding to 100 groups of chromosomes1,H2,…,Hi,…,H100；
S42: optimizing the installation position of the capacitance blocking device based on a genetic algorithm, and adopting a roulette selection method of random traversal sampling, wherein the population cross probability is 0.6, the gene variation probability is 0.2, and the iteration number is 200;
s43: after iteration is terminated, the chromosome corresponding to the minimum target result meeting the constraint condition is an optimal inhibition strategy, and 1 in the chromosome is the installation position of the capacitance blocking device.
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CN107147095A (en) * 2017-05-25 2017-09-08 华中科技大学 A kind of direct current and spuious harmonic current of suppressing is into the device of transformer neutral point
CN108521114A (en) * 2018-05-10 2018-09-11 四川大学 A kind of Optimal Configuration Method of transformer neutral point capacitance blocking device
CN110994552A (en) * 2019-12-05 2020-04-10 华中科技大学 Autonomous switching method of neutral point ground current suppression device of transformer
CN111338233A (en) * 2020-03-03 2020-06-26 西南交通大学 Simulation modeling method for subway stray current distribution in urban power grid

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Publication number Priority date Publication date Assignee Title
CN102792538A (en) * 2010-03-15 2012-11-21 西门子工业公司 Method and apparatus for supervisory circuit for ground fault circuit interrupt device
JP2013247725A (en) * 2012-05-24 2013-12-09 Hitachi Ltd Electric power conversion system
CN107147095A (en) * 2017-05-25 2017-09-08 华中科技大学 A kind of direct current and spuious harmonic current of suppressing is into the device of transformer neutral point
CN108521114A (en) * 2018-05-10 2018-09-11 四川大学 A kind of Optimal Configuration Method of transformer neutral point capacitance blocking device
CN110994552A (en) * 2019-12-05 2020-04-10 华中科技大学 Autonomous switching method of neutral point ground current suppression device of transformer
CN111338233A (en) * 2020-03-03 2020-06-26 西南交通大学 Simulation modeling method for subway stray current distribution in urban power grid

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