CN111339624B - PSASP and EMTP/ATP-based short-circuit current direct-current component calculation method - Google Patents
PSASP and EMTP/ATP-based short-circuit current direct-current component calculation method Download PDFInfo
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Abstract
The invention relates to a power modeling and simulation technology, in particular to a PSASP and EMTP/ATP short-circuit current direct current component calculation method, which is used for dividing a regional power grid into an internal power grid and an external power grid, setting an analyzed line as the internal power grid, setting other parts as the external power grid, modeling the internal power grid and carrying out equivalent simplification on the external power grid; the node between the external power grid and the internal power grid is a boundary node; the external power grid equivalence is simplified into a multi-terminal network with only boundary nodes, and the multi-terminal network comprises injection current sources of the boundary nodes, node self admittances and mutual admittances among the nodes; setting a short-circuit fault by PSASP software, solving an injection current source and an admittance matrix of a boundary node after the equivalence of an external power grid, establishing an internal power grid and an external power grid model after the equivalence in EMTP/ATP, setting the short-circuit fault, and obtaining a short-circuit current direct-current component from simulation. The method combines the characteristics of the mathematical model of the complex power system network, has accurate calculation result, is simple, convenient and feasible, and is convenient for engineering routine calculation.
Description
Technical Field
The invention belongs to the technical field of power modeling and simulation, and particularly relates to a PSASP and EMTP/ATP-based short-circuit current direct current component calculation method.
Background
With the development of power systems, the connection between power supplies is tighter and tighter, and the problem of exceeding the short-circuit capacity of the system is also more and more prominent. At present, only periodic components are considered in routine checking of the breaking capacity of the circuit breaker in China, the influence of direct current components on the breaking capacity of the circuit breaker is not considered, but the direct current components of short circuit currents have certain influence on normal breaking of the circuit breaker, and particularly under the condition that the breaking capacity margin of the circuit breaker is smaller and the direct current components of short circuit currents are attenuated more slowly, the attenuation characteristics of the direct current components of the short circuit currents are accurately and effectively analyzed, and the method has important significance for ensuring that the circuit breaker of a power grid can normally break short circuit currents of a system and the breaking failure influence on the power supply reliability due to overlarge arc energy and electrodynamic force.
However, the current calculation of the attenuation of the dc component of the short-circuit current has been lacking in methods and tools that are simple and practical in engineering. The short-circuit current calculation standard describes the periodic component calculation more, but the calculation of the decay time constant of the complex network is not clearly defined. The existing complex network short-circuit current direct-current component calculation method comprises a limiting frequency method, a two-branch equivalent network method and an equivalent frequency method. The limiting frequency method is effective only when the time constants of the branches are not different greatly; the two-branch method can only process two branches at a time, and the time constant of one branch must be fixed in advance, so that the method is inconvenient to use in a multi-power mesh network; the essence of the two is to perform equivalent transformation on the power network described by the power frequency impedance, so that the equivalent impedance under the power frequency is used for participating in the calculation of the direct current component without frequency characteristicWhether the amount of attenuation is correct or not is difficult to determine. Equivalent frequency method, which is to select corresponding equivalent frequency f according to the focused different time table c Calculate the equivalent impedance Z c However, the method needs to calculate the equivalent frequency at different moments after the short circuit and calculate the equivalent impedance under the corresponding equivalent frequency, thereby greatly increasing the calculation workload.
The periodic component and the non-periodic component of the short-circuit current which consider attenuation need to be accurately researched and calculated, three-phase full-phase modeling can be carried out by means of electromagnetic transient simulation software EMTP, and then the corresponding direct-current component is separated from the short-circuit full-current instantaneous value waveform obtained through simulation. When EMTP modeling is used, the difficulty is that when the number of equivalent power grid nodes reaches thousands, the equivalent calculation workload is huge, and the power grid equivalent outside the area needs to be simplified. In the traditional power grid equivalence method, such as Ward and REI equivalence, when the equivalent power grid is large, the nodes to be eliminated by Gaussian elimination are excessive, the equivalent power grid becomes difficult to solve, all node voltages of the equivalent power grid are involved in the admittance matrix solving process, and the workload is huge. The domestic calculation of the attenuation of the direct current component of the short-circuit current is always lacking in a simple and practical engineering method and tool.
Disclosure of Invention
The invention aims to provide a method for calculating a short-circuit current direct-current component based on PSASP short-circuit fault simulation and EMTP/ATP electromagnetic transient simulation equivalent network.
In order to achieve the above purpose, the invention adopts the following technical scheme: dividing a regional power grid into an internal power grid and an external power grid based on PSASP and EMTP/ATP short-circuit current direct-current component calculation methods, setting an analyzed line as the internal power grid, and modeling the internal power grid by other parts as the external power grid, and performing equivalent simplification on the external power grid; the node between the external power grid and the internal power grid is a boundary node; the external power grid equivalence is simplified into a multi-terminal network with only boundary nodes, and the multi-terminal network comprises injection current sources of the boundary nodes, node self admittances and mutual admittances among the nodes; setting a circuit breaking and short circuit fault by PSASP software, solving an injection current source and an admittance matrix of the boundary node, and calculating a short circuit current direct current component by EMTP/ATP; the method comprises the following steps:
step 1, isolating an internal network from PSASP software in a three-phase disconnection fault mode, and performing short circuit calculation on an external power grid only;
step 2, carrying out simultaneous three-phase short circuit on all boundary nodes in PSASP software, calculating to obtain short circuit branch current of each boundary node, and solving an injection current source of a positive sequence network;
step 3, carrying out three-phase short circuit on each boundary node one by one, calculating to obtain positive sequence current of a short circuit branch and positive sequence voltage of the boundary node through PSASP software, and solving a positive sequence admittance matrix of the boundary node;
step 4, single-phase short circuit is carried out on the boundary nodes one by one, zero-sequence currents of short circuit branches and zero-sequence voltages of the boundary nodes are obtained through PSASP software calculation, and a zero-sequence admittance matrix of the boundary nodes is solved;
and 5, building an internal power grid and an external power grid model after equivalent in EMTP/ATP according to the injection current source, the positive sequence admittance matrix and the zero sequence admittance matrix of the positive sequence network calculated in the steps 1-4, setting a short circuit fault, and separating a corresponding direct current component from a short circuit full current instantaneous value waveform.
The invention has the beneficial effects that: the invention utilizes simulation software PSASP to simulate disconnection and short circuit faults, further obtains an admittance matrix by matrix operation, simplifies the equivalence of a large-scale power grid example, reconstructs a complete equivalence network in an electromagnetic transient simulation program EMTP/ATP, and utilizes the EMTP/ATP to calculate a short circuit current direct current component. The calculation amount is small in the equivalence process, and the calculation result is accurate, simple, convenient and feasible by combining the characteristics of the mathematical model of the complex power system network, so that the engineering routine calculation is facilitated.
Drawings
FIG. 1 is a model of an equivalent network according to one embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
And carrying out electromagnetic transient analysis on local lines and nearby areas of a large-scale local power grid by using an electromagnetic transient simulation program EMTP/ATP, and establishing a power grid model taking the analyzed lines as a main body to carry out equivalent simplification on other parts of the power grid. The PSASP software of the power system analysis comprehensive program widely applied to the power department can construct a database of a large-scale network with tens of thousands of nodes, a power grid model of a plurality of provinces related to the extra-high voltage line is already built, more than 7000 nodes are arranged, on the basis, the simulation software PSASP is utilized to simulate disconnection and short circuit faults, an admittance matrix is obtained through matrix operation, equivalence simplification is carried out on a large-scale power grid instance, and a complete equivalent network is reconstructed in an electromagnetic transient simulation program EMTP/ATP. The embodiment provides a PSASP and EMTP/ATP short-circuit current direct current component calculation method.
The regional power grid is divided into an internal power grid and an external power grid, the analyzed line is the internal power grid, detailed modeling is needed, and the external power grid is simplified. The node between the external grid and the internal grid is a boundary node. After the external power grid is subjected to equivalent simplification, the external power grid is a multi-terminal network only provided with boundary nodes, and the multi-terminal network comprises injection current sources of the boundary nodes, node self admittances and mutual admittances among the nodes. And setting a short-circuit fault in PSASP software, solving an injection current source and an admittance matrix of boundary nodes after the external power grid is equivalent, building an internal power grid and an external power grid model after the external power grid is equivalent in EMTP/ATP, setting the short-circuit fault, and then separating a corresponding direct current component from a short-circuit full-current instantaneous value waveform obtained by simulation.
And firstly, isolating the internal power grid from PSASP software in the form of three-phase disconnection faults, and performing short circuit calculation on the external power grid only. The network is reserved as an internal power grid, and the other networks are external power grids. The number of lines connecting the internal and external power grids is large, and the process is completed in PSASP software in the form of line disconnection fault operation.
And secondly, carrying out simultaneous three-phase short circuit on all boundary nodes in PSASP software, and calculating to obtain short circuit branch current of each boundary node. Because the voltage of each boundary node is zero, the short-circuit branch current of each boundary node is equal to the injection current source of the node in the external power grid after the equivalence. Because the external power grid after the equivalence has only boundary nodes, the injection current source, the positive sequence admittance matrix and the zero sequence admittance matrix of the boundary nodes after the equivalence of the external power grid need to be solved based on PSASP software short-circuit calculation. The general negative sequence network and the zero sequence network are passive networks, and only the injection current source of the positive sequence network needs to be solved.
Thirdly, three-phase short circuit is conducted on each boundary node one by one, positive sequence current of a short circuit branch and positive sequence voltage of the boundary node are obtained through PSASP software calculation, then according to the obtained injection current source of the boundary node in the external positive sequence network after equivalent value, node voltage equations of each short circuit are respectively listed, and a positive sequence admittance matrix of the boundary node can be obtained through simultaneous solving.
And fourthly, carrying out single-phase short circuit on the boundary nodes one by adopting the same method, calculating to obtain the zero sequence current of the short circuit branch and the zero sequence voltage of the boundary nodes through PSASP software, respectively writing node voltage equations of each short circuit, and solving simultaneously to obtain the zero sequence admittance matrix of the boundary nodes. It should be noted that, the injection current source of the boundary node is in positive sequence, so for the zero sequence network, the injection current source of the boundary node is zero.
And fifthly, an internal power grid and an external power grid model after equivalent are built in the EMTP/ATP, a short circuit fault is set, and corresponding direct current components are separated from short circuit full-current instantaneous value waveforms obtained through simulation.
Taking a power grid with 5-point boundary nodes as an example, the external power grid equivalent network is shown in fig. 1, and injection current sources of all nodes are marked in the figureAnd admittances of the individual branches. All nodes, branches and related parameters of the equivalent network are already established in the PSASP software.
(1) And removing nodes and branches of the internal power grid of the equivalent network, and reserving a part of the network, namely the external power grid.
(2) The 4 boundary nodes 1, 2, 3, 4 and 5 in fig. 1 have metallic short circuits at the same time, and the voltages of the 5 nodes are all zero, and all the nodes in the diagram are equipotential, so that the current of admittance branches of the 4 boundary nodes in fig. 1 is zero.Taking boundary node 1 as an example, y l0 、y 12 、y 13 、y 14 、y 15 The branch currents are all zero. The current I of the short-circuit branch can be obtained through PSASP software calculation f1 According to kirchhoff's current law, this current is equal to the injection current source I 1 . Injection current sources for other 2, 3, 4, 5 boundary nodes are available in the same manner.
(3) And carrying out three-phase short circuit on each boundary node one by one, calculating and obtaining positive sequence current of a short circuit branch and positive sequence voltage of 5 boundary nodes through PSASP software, respectively writing node voltage equations of each short circuit, and solving simultaneously to obtain a positive sequence admittance matrix of the boundary nodes. Firstly, taking the boundary node l of fig. 1 as an example, the node l is in metallic short circuit, and the positive sequence current I of the short circuit branch can be obtained through PSASP software calculation f1 And positive sequence voltage of 5 boundary nodes, injection current source of each nodeThe node voltage equation can thus be written in columns:
wherein: the 1 st item on the left of the equal sign is the admittance matrix of these 5 points, the self admittance Y 11 ＝y l0 +y l2 +y l3 +y 14 +y 15 Transadmittance Y 12 ＝-y 12 ，Y 13 ＝-y 13 ，Y 14 ＝-y 14， Y 15 ＝-y 15， The method comprises the steps of carrying out a first treatment on the surface of the The 2 nd item on the left of the equal sign is the voltage of 5 boundary nodes when the boundary node 1 is short circuited; i f1 Is the node 1 short circuit branch current; to the right of the equal sign is an injection current source of 5 points.
Similarly, if three-phase short circuit calculation is performed at the nodes 2, 3, 4, 5, the same is true:
the synthesis (1-1) (1-2) (1-3) (1-4) (1-5) can be obtained:
and (3) performing matrix inversion calculation according to the voltage matrix and the current matrix obtained by short circuit calculation in the formulas (1-6) to obtain an admittance matrix of the boundary node. The dimension of the matrix operation is equal to the number of boundary nodes, the calculated amount is small, and the matrix operation can be completed by Matlab software.
(4) And carrying out single-phase short circuit on each boundary node one by one, calculating and obtaining the zero sequence current of a short circuit branch and the zero sequence voltage of 5 boundary nodes through PSASP software, respectively writing node voltage equations of each short circuit, and simultaneously solving to obtain the zero sequence admittance matrix of the boundary node. The injection current source of the boundary node is zero, and the current matrix in the formula (1-6) only comprises the zero sequence current of the short circuit branch.
(5) Injection current source for setting up boundary nodes after internal power grid and external power grid are equivalent in EMTP/ATPAdmittance y 10 、y 20 、y 30 、y 40 、y 50 Setting short-circuit fault, and separating corresponding direct current component from the short-circuit full-current instantaneous value waveform obtained by simulation.
It should be understood that parts of the specification not specifically set forth herein are all prior art.
While particular embodiments of the present invention have been described above with reference to the accompanying drawings, it will be understood by those skilled in the art that these are by way of example only, and that various changes and modifications may be made to these embodiments without departing from the principles and spirit of the invention. The scope of the invention is limited only by the appended claims.
Claims (1)
1. The method is characterized in that a regional power grid is divided into an internal power grid and an external power grid, an analyzed line is set as the internal power grid, other parts are set as the external power grid, the internal power grid is modeled, and the external power grid is subjected to equivalent simplification; the node between the external power grid and the internal power grid is a boundary node; the external power grid equivalence is simplified into a multi-terminal network with only boundary nodes, and the multi-terminal network comprises injection current sources of the boundary nodes, node self admittances and mutual admittances among the nodes; setting broken line and short circuit faults by PSASP software, solving an injection current source and an admittance matrix of the boundary node, and calculating a short circuit current direct current component by EMTP/ATP; the method comprises the following steps:
step 1, isolating an internal network from PSASP software in a three-phase disconnection fault mode, and performing short circuit calculation on an external power grid only;
step 2, carrying out simultaneous three-phase short circuit on all boundary nodes in PSASP software, calculating to obtain short circuit branch current of each boundary node, and solving an injection current source of a positive sequence network;
step 3, carrying out three-phase short circuit on each boundary node one by one, calculating to obtain positive sequence current of a short circuit branch and positive sequence voltage of the boundary node through PSASP software, and solving a positive sequence admittance matrix of the boundary node;
step 4, single-phase short circuit is carried out on the boundary nodes one by one, zero-sequence currents of short circuit branches and zero-sequence voltages of the boundary nodes are obtained through PSASP software calculation, and a zero-sequence admittance matrix of the boundary nodes is solved;
and 5, building an internal power grid and an external power grid model after equivalent in EMTP/ATP according to the injection current source, the positive sequence admittance matrix and the zero sequence admittance matrix of the positive sequence network calculated in the steps 1-4, setting a short circuit fault, and separating a corresponding direct current component from a short circuit full current instantaneous value waveform.
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| CN103605829A (en) * | 2013-10-22 | 2014-02-26 | 华中科技大学 | Equivalent model method for performing electromagnetic transient simulation on alternating current/direct current hybrid power grid |
| CN105243232A (en) * | 2015-11-03 | 2016-01-13 | 国家电网公司 | Electromagnetic transient simulation method and system for integrating field analysis into electric network to determine |
| JP2017184337A (en) * | 2016-03-28 | 2017-10-05 | 株式会社東芝 | Overvoltage prevention apparatus for adjustable speed pumped storage power generation system |
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| CN101957398A (en) * | 2010-09-16 | 2011-01-26 | 河北省电力研究院 | Method for detecting and calculating primary time constant of power grid based on electromechanical and electromagnetic transient hybrid simulation technology |
| CN103605829A (en) * | 2013-10-22 | 2014-02-26 | 华中科技大学 | Equivalent model method for performing electromagnetic transient simulation on alternating current/direct current hybrid power grid |
| CN105243232A (en) * | 2015-11-03 | 2016-01-13 | 国家电网公司 | Electromagnetic transient simulation method and system for integrating field analysis into electric network to determine |
| JP2017184337A (en) * | 2016-03-28 | 2017-10-05 | 株式会社東芝 | Overvoltage prevention apparatus for adjustable speed pumped storage power generation system |
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