CN104659779B - Selection method of mutual supply and contact mode in power grid divisions - Google Patents

Abstract

A method for selecting power exchange connection modes for sub-areas in a power grid comprises steps as follows: A, power grid parameters of a fault sub-area and an adjacent sub-area are acquired; B, power vacancy of the fault sub-area is determined; C, exchange power of all connecting lines in the fault sub-area is determined; D, whether a main transformer down channel of the fault sub-area is broken down is judged, if yes, one connecting line with the highest exchange power is closed to be taken as an exchange connecting channel, and otherwise, a buscouple switch is switched off to be taken as the exchange connecting channel; E, whether the power vacancy of the fault sub-area is met is judged, if yes, a step F is executed, and otherwise, a step G is executed; F, whether the exchange connecting channel is overloaded is judged, if yes, the step G is executed, and otherwise, the connecting way is selected; G, one connecting line is added as the exchange connecting channel, and the step E is executed. According to the method for selecting the power exchange connection modes for the sub-areas in the power grid, the effective power grid sub-area exchange ways can be provided, and the system stability is improved.

Description

Selection method of mutual supply and contact mode in power grid divisions

technical field

The invention relates to the field of power system operation, in particular to the fault processing technology in the partition operation mode of the power system.

Background technique

Driven by the continuous development and improvement of the 500kV grid structure, the urban power grid has gradually formed a network structure in which the main grid is a 500kV ring network and the regional grid is a 220kV grid. At the same time, the 500/220kV high and low voltage electromagnetic ring network and the increase of short-circuit current in the 220kV side system have become increasingly prominent with the continuous strengthening of network connections. Therefore, the implementation of the grid partition operation mechanism with 500kV substations as the core should be promoted. . After forming a reasonable partition, the 500/220kV electromagnetic ring network that seriously affects the safety and stability of the power grid can be eliminated, the instability problem of the electromagnetic ring network can be solved, and a small number of unit units and regional power plants of newly established large-capacity power plants can be directly connected to the transformation For the 220kV power grid of the distribution network, the radiation grid is used to supply the power load, which effectively reduces the short-circuit current level of the system and simplifies relay protection and operation.

While the 220kV power grid partition operation mode brings the aforementioned advantages, it also weakens the accident resistance ability of each partition. To this end, it is necessary to build a mutual supply communication channel between the 220kV power grid partitions to ensure the reliability of the power supply of the 500kV main transformer as the partition power supply and hub in the fault or maintenance time zone, without load shedding or as little as possible load shedding.

Since the partitions can adopt various methods for partition mutual supply, such as adopting different mutual supply communication channels, or directly using the 220kV side bus tie switch as the mutual supply communication channel, so when the main transformer of a certain partition fails or is overhauled, How to determine the low-cost and effective communication method of regional mutual supply has become a problem worthy of research. The choice of inter-regional mutual supply and contact mode is directly related to the power exchange and support level between the regions, and affects the power transmission capability between the regions. Unreasonable choice of mutual supply and contact mode will make the power balance demand of the power grid in the accident mode unsatisfied. However, in the prior art, there is no reasonable selection method for the determination of mutual supply contact methods, which makes the selection of mutual supply contact methods diverse and random, which brings hidden dangers to the safe operation of the power grid.

Contents of the invention

In view of this, the purpose of the present invention is to overcome the deficiencies in the prior art, to provide a method for selecting a grid partition mutual supply contact mode, to provide an effective solution for the selection of the grid partition mutual supply contact mode, so as to improve the reliability of the grid operation security and stability.

In order to achieve this goal, the technical solution adopted by the present invention is as follows.

A method for selecting a power grid partition mutual supply contact mode, the method comprising the following steps:

A. Obtain the grid parameters of the fault zone and adjacent zones;

B. Determine the power deficit of the fault zone;

C. Determine the mutual power supply of all tie lines in the fault zone;

D. Judging whether the transmission channel of the main transformer in the fault zone is faulty, if it is faulty, close the tie line with the largest mutual power supply as the mutual supply communication channel, otherwise close the bus tie switch as the mutual supply communication channel;

E. Judging whether the power shortage of the faulty partition is satisfied, if it is satisfied, execute step F, otherwise execute step G;

F. Judging whether the mutual supply communication channel is overloaded, if it is overloaded, execute step G, otherwise select the communication method;

G. Add a connection line as a mutual supply communication channel, and execute step E.

In step A, acquiring the grid parameters of the fault zone and adjacent zones includes: acquiring equivalent impedances of the fault zone and adjacent zones.

In addition, in step B, it is determined that the power deficit of the faulty partition is:

Among them, P _loss is the power loss in the partition when the main transformer N-2 fault occurs in the fault partition,

x _sf and x _ss are equivalent impedances from other normal main transformers to the compensation point in the zone.

In step C, determining the mutual power supply of all tie lines in the fault zone includes:

${\mathrm{<span\; class="notranslate">\; P</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{<span\; class="notranslate">\; *</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;\&delta;</span>}<span\; class="notranslate">\; ,</span>$

Among them, P ^* is the per unit value of mutual active power,

In order to connect the equivalent impedance of the mutual supply system,

Δδ is the phase angle variation of the contact point of the fault zone.

Determining the Equivalent Impedance of the Communication and Mutual Supply System include:

C1. Determine the equivalent impedance of the two partitions to the contact point as:

x ₁ =JX _A J ^T and x ₂ =KX _B K ^T ,

Where X _A and X _B are the node impedance matrices of the two partitions respectively,

is an m-dimensional row vector, point j is the position of the contact point in partition A, and m is the total number of nodes in partition A;

is an n-dimensional row vector, k points are the positions of contact points in partition B, and n is the total number of nodes in partition B;

C2. According to the impedance of the communication channel itself and the equivalent impedance of the two partitions to the contact point, determine the equivalent impedance of the communication and mutual supply system.

In addition, the determination of the phase angle variation Δδ of the fault zone connection includes:

Δδ=X ^* P _Δ ^* ,

where X ^* is the per unit value of the node impedance matrix in the fault zone,

P _Δ ^* is a vector composed of per-unit values of injected power variation of each node under fault conditions.

By adopting the selection method of the grid partition mutual supply and contact mode of the present invention, it is possible to address the problems existing in the selection of the inter-zone mutual supply and contact mode after the grid is partitioned, and propose a selection method for the inter-zone mutual supply and contact mode, which improves the operation of the grid partitions. power supply security and reliability.

Description of drawings

Fig. 1 is a schematic flowchart of a method for selecting a communication mode for mutual supply and supply between power grid subregions in a specific embodiment of the present invention.

Fig. 2 is an equivalent circuit diagram of a closed communication channel of a partitioned power grid in a specific embodiment of the present invention.

Fig. 3 is a wiring diagram of the Changcheng district and adjacent districts of a specific application example of the present invention.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings.

Detailed exemplary embodiments are disclosed below. However, specific structural and functional details disclosed herein are merely for purposes of describing example embodiments.

It should be understood, however, that the invention is not limited to the particular exemplary embodiments disclosed, but covers all modifications, equivalents, and alternatives falling within the scope of the disclosure. Throughout the description of the figures, the same reference numerals denote the same elements.

Also, it should be understood that as used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. Also it will be understood that when a component or unit is referred to as being “connected” or “coupled” to another component or unit, it can be directly connected or coupled to the other component or unit or intervening components or units may also be present. Also, other words used to describe the relationship between elements or elements should be interpreted in the same fashion (eg, "between" versus "directly between," "adjacent" versus "directly adjacent," etc.).

In order to illustrate the technical solution of the present invention, the technical principle of the present invention is firstly introduced.

In the embodiment of the present invention, the power shortage in the fault zone refers to the grid zone with non-independent power supply reliability. When the 500kV main transformer N-2 fault occurs, in order to meet the power balance in the zone, the required The power for mutual support between adjacent areas through communication channels.

The power grid partition with non-independent power supply reliability refers to that when the 500kV main transformer N-2 fault occurs in the 220kV power grid partition area, it can still satisfy its own power balance and ensure reliable power supply to the electric load without the need for adjacent partitions. Mutual supply and support, the partition is a grid partition with independent power supply reliability. Otherwise, it is a power grid partition with non-independent power supply reliability, and it is necessary for adjacent partitions to provide mutual support through communication channels to meet the power balance in the region and ensure its safe and stable operation.

The principle of the technical solution of the present invention is described in the simplest way including two partitions, but the scope of application of the present invention is not limited thereto, for example, it can be extended to the situation where there are multiple partitions. There are two partitions A and B. Let B partition be a power grid partition with non-independent power supply reliability. When the 500kV main transformer N-2 fault occurs in B partition, the adjacent partition A is required to provide mutual support. Let the fault point be f, then the fault point information matrix in partition B is:

is an n-dimensional row vector, and n is the total number of nodes.

Then the node injection power variation under fault is:

P _Δ ＝F ^T ·P _loss (1)

Among them, P _loss is the power loss in the partition when the 500kV main transformer N-2 fault occurs in the fault partition.

When the main transformer N-2 fault occurs in a 500kV substation in the fault zone, the other 500kV main transformers in the zone will send more power to reduce the power loss in the zone, and try to keep the phase angle of the 220kV bus voltage unchanged. Therefore, for a power grid partition, after a 500kV power station in the region has a main transformer N-2 fault, assuming that the 220kV bus of other 500kV stations in the region is located at point s in the region, the compensation power is:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; add</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; sf</span>}}^{<span\; class="notranslate">\; *</span>}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; ss</span>}}^{<span\; class="notranslate">\; *</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; loss</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Therefore, the faulty partition power deficit is:

Among them, x _sf and x _ss are equivalent impedances from other normal main transformers to compensation points in the subregion.

The mutual supply power of the communication channel is to quantitatively discuss the influence of different factors on the mutual supply power of the communication channel. It is necessary to simplify the analysis of the mutual supply and closing point circuit, and the Thevenin's theorem is introduced to realize the analysis and calculation of the mutual supply power. Figure 2 shows the equivalent circuit diagram of the closed communication channel of the partitioned power grid.

As shown in Fig. 2, when the communication channel is closed, it is equivalent to connecting an impedance z _td in parallel between nodes i and j. If the 220kV tie line is used as the mutual supply connection mode, then z _td is the line impedance; if the 500kV main transformer 220kV side bus tie switch is used as the mutual supply connection mode, then z _td is zero. When the equivalent Thevenin equivalent impedance of the partition grid to the partition contact point is z ₀ , the total equivalent impedance of the connection and mutual supply system is z=z ₀ +z _td =r _Σ +jx _Σ . Mutual Supply Tie Point Voltage of Fault Zone As a reference phasor, let the mutual supply power caused by the voltage drop of the mutual supply contact point be S=P+jQ, where:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}$

According to the dispatching operation rules, before closing the communication channel for mutual supply, the voltage amplitude difference and power angle difference of the mutual supply contact points of the two partitions should be controlled within 5% and 15° respectively, that is, |δ _ij |<15°, and r _Σ << x _Σ , so the approximate conditions cosδ _ij ≈1, sinδ _ij ≈δ _ij are satisfied. Therefore:

$\mathrm{<span\; class="notranslate">\; P</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

$\mathrm{<span\; class="notranslate">\; Q</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

Comparing the mutual supply of active power and reactive power, there are:

$\frac{\mathrm{<span\; class="notranslate">\; P</span>}}{\mathrm{<span\; class="notranslate">\; Q</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

Since the mutual supply communication channel is located in the 220kV power grid, according to the operation requirements of the loop closure, the voltage amplitude difference before the loop closure is controlled within 5%, so |U _i -U _j |≤11kV; and |δ _ij |<15°(0.262rad ), then according to formula (7), the size of the active power flow is 4 to 6 times that of the reactive power flow, so the mutual supply of reactive power Q has little influence on the mutual supply power S, and the mutual supply power S and mutual supply The active power P is basically close.

For the mutual supply of active power, before closing the communication channel, the voltage amplitude difference between the mutual supply contact points of the two partitions needs to be controlled within 5%, and the voltage amplitude is mainly affected by the reactive power balance, and the latter is applicable to layered on-site Therefore, it can be considered that the voltages of the mutual supply contact points of the two partitions are operating near the rated voltage, and the phase angle difference of the contact point of the partition is approximately the change in the phase angle of the contact point of the faulty partition. Therefore, the mutual supply active power represented by per unit value is:

${\mathrm{<span\; class="notranslate">\; P</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{<span\; class="notranslate">\; *</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;\&delta;</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

The equivalent impedance of the connection and mutual supply system is inversely proportional to the mutual supply active power. To calculate the mutual supply active power, the equivalent impedance of the connection and mutual supply system is calculated first.

The node impedance matrix of the partitioned power grid is introduced, and the network equation represented by the node impedance matrix Z is:

ZI _B =U _B (9)

Z _ii represents the equivalent impedance parameter of the partition grid. According to its physical meaning, it is the equivalent impedance seen from node i to the partition, that is, the equivalent impedance of the partition grid to node i, and there is |Z _ii | ≥ |Z _ij |.

Assume that two adjacent partitions in the partition grid are A partition and B partition respectively. Among them, the A partition has m nodes in total, and the contact point with the B partition is the j point among them; the B partition has n nodes in total, and the contact point with the A partition is the k point among them.

Then the contact point matrices of the two partitions for mutual supply and mutual supply are:

Partition A: is an m-dimensional row vector;

Partition B: is an n-dimensional row vector.

If the node impedance matrices of A and B partitions are respectively X _A and X _B , then the equivalent impedances of A and B partitions to contact points are respectively:

Partition A:

x ₁ ＝x _jj ＝JX _A J ^T (10)

Partition B:

x ₂ ＝x _kk ＝KX _B K ^T (11)

Combined with the impedance x _td of the communication channel itself, the equivalent impedance x _Σ of the communication and mutual supply system can be obtained.

The change in phase angle of the contact point in the fault zone is directly proportional to the mutual supply active power. In order to calculate the active power in mutual supply, it is also necessary to calculate the change in phase angle of the contact point in the fault zone.

The polar coordinate form of the branch power equation between two nodes i and j in the partition grid s is:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; j</span>}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

Among them, G _ij and B _ij are related elements in the admittance matrix of partition nodes. Therefore, there are:

${\mathrm{<span\; class="notranslate">\; G</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}}{{\mathrm{<span\; class="notranslate">\; r</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 13</span>}<span\; class="notranslate">\; )</span>$

For high-voltage transmission networks, the line reactance value is much greater than the resistance value. Therefore, |G _ij |<<|B _ij |, sinδ _ij ≈δ _ij , cosδ _ij ≈1, only considering branch ij, then G _ii =-G _ij , B _ii =-B _ij . So there are:

${\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}^{<span\; class="notranslate">\; *</span>}{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&delta;</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; ij</span>}}^{<span\; class="notranslate">\; *</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 14</span>}<span\; class="notranslate">\; )</span>$

Since the active power of a node is equal to the sum of the power flowing through its related branches, that is And the node impedance matrix and the node admittance matrix are inverses of each other, so:

δ = (B ^-1 ) ^* P ^* = X ^* P ^* (15)

Therefore, the phase angle variation vector of partition nodes under fault conditions is:

Δδ = X ^* P _Δ ^* (16)

Therefore, for the aforementioned partitions A and B, the change in phase angle of the contact point of the faulty partition B can be expressed as:

$\mathrm{<span\; class="notranslate">\; \&Delta;\&delta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; KX</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}^{<span\; class="notranslate">\; *</span>}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; \&Delta;</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 17</span>}<span\; class="notranslate">\; )</span>$

Therefore, as shown in FIG. 1, the method for selecting a communication mode for mutual supply between power grid partitions in the embodiment of the present invention includes the following steps:

A. Obtain the grid parameters of the fault zone and adjacent zones;

B. Determine the power deficit of the fault zone;

C. Determine the mutual power supply of all tie lines in the fault zone;

D. Judging whether the transmission channel of the main transformer in the fault zone is faulty, if it is faulty, close the tie line with the largest mutual power supply as the mutual supply communication channel, otherwise close the bus tie switch as the mutual supply communication channel;

E. Judging whether the power shortage of the faulty partition is satisfied, if it is satisfied, execute step F, otherwise execute step G;

F. Judging whether the mutual supply communication channel is overloaded, if it is overloaded, execute step G, otherwise select the communication method;

G. Add a connection line as a mutual supply communication channel, and execute step E.

Therefore, adopting the method for selecting the interconnection mode of inter-supply of power grids in the present invention can adopt the most economical and effective way to achieve inter-supply of power grids.

Wherein, acquiring the power grid parameters of the fault zone and adjacent zones includes: acquiring equivalent impedances of the fault zone and adjacent zones.

In addition, according to the aforementioned analysis, it is determined that the power deficit of the fault partition is:

Among them, P _loss is the power loss in the partition when the main transformer fails in the fault partition,

x _sf and x _ss are the equivalent impedances of other normal main transformer compensation points in the zone.

And to determine the mutual power supply of all tie lines in the fault zone includes:

${\mathrm{<span\; class="notranslate">\; P</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{{\mathrm{<span\; class="notranslate">\; x</span>}}_{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}^{<span\; class="notranslate">\; *</span>}}\mathrm{<span\; class="notranslate">\; \&Delta;\&delta;</span>}<span\; class="notranslate">\; ,</span>$

Among them, P ^* is the per unit value of mutual active power,

In order to connect the equivalent impedance of the mutual supply system,

Δδ is the phase angle variation of the fault zone connection.

Among them, determine the equivalent impedance of the contact mutual supply system include:

C1. Determine the equivalent impedance of the two partitions to the contact point as:

x ₁ =JX _A J ^T and x ₂ =KX _B K ^T ,

Where X _A and X _B are the node impedance matrices of the two partitions respectively,

is an m-dimensional row vector, point j is the position of the contact point in partition A, and m is the total number of nodes in partition A;

is an n-dimensional row vector, k points are the positions of contact points in partition B, and n is the total number of nodes in partition B;

C2. According to the impedance of the communication channel itself and the equivalent impedance of the two partitions to the contact point, determine the equivalent impedance of the communication and mutual supply system.

And the determination of the phase angle variation Δδ of the fault zone connection includes:

Δδ=X ^* P _Δ ^* ,

where X ^* is the per unit value of the node impedance matrix in the fault zone,

P _Δ ^* is a vector composed of per-unit values of injected power variation of each node under fault conditions.

The technical effects of the present invention will be described below through a specific example, and those skilled in the art should be clear that the specific example is only exemplary and cannot itself constitute a limitation to the present invention.

The circuit topology diagram of the example is shown in FIG. 3 , which takes Beijing's 2015 planned power grid as an example to calculate and verify the feasibility of the method and process for mutual supply of power grids in the present invention. Through BPA calculation and analysis, it can be seen that Changcheng sub-area has non-independent power supply reliability, and other areas need to provide mutual support in case of failure. Figure 3 is the wiring diagram of Changcheng District and adjacent districts. After the 500kV Changping 2# and 3# main transformer N-2 faults occurred in Changcheng District, the adjacent Chengshunchao District will provide mutual support. In the following, the selection of the contact method for regional mutual supply will be carried out according to the flow of the method for selecting the regional mutual supply contact method of the present invention.

Step 1: Obtain the grid parameters of the fault zone and adjacent zones.

After the failure of the equipment, the adjacent Chengshunchao sub-area will provide power support. According to the power grid parameters of Chengshunchao sub-region and Changcheng sub-region, relevant equivalent impedance data can be obtained.

The equivalent impedance of Chengshunchao sub-area x ₁ = 3.65Ω, the equivalent impedance of Changcheng sub-area x ₂ = x _ff = 2.71Ω, the equivalent impedance of the normal main transformer 500kV Chengbei 2# substation compensation point in Changcheng sub-area x _ss = 3.96Ω , x _sf =2.30Ω. 220kV Changping = Huairou Double Circuit x _td1 = 0.82Ω, x _kf1 = 2.45Ω, Qijiazhuang = Future City Double Circuit x _td2 = 0.80Ω, x _kf2 = 2.15Ω.

Step 2: Calculate the power deficit of the faulty partition.

According to the capacity and load of the 500kV main transformer in the Changcheng sub-area before the fault, it can be known that the power loss value of the sub-area is P _loss = 808.53MW. The power compensation value of the main transformer in normal operation in Changcheng sub-region under failure is P _add = 469.60MW. Therefore, the power deficit under a fault is P loss = P _loss - P _add = _338.93 MW.

Step 3: Use the AC line as the communication method for mutual supply.

When the AC line port is selected, it has a similar port equivalent impedance to the bus tie switch port. Under this condition, the effectiveness of the method for selecting the mutual supply and contact mode of the grid partition based on the equivalent impedance is determined.

After comparative analysis, Yuguanying and Nanyuan are selected as the two ends of the AC line connection mode, and the equivalent impedance of the port system is calculated. Before closing the ring, the voltage amplitude and phase angle difference of Yuguanying and Nanyuan 220kV buses are shown in Table 1.

Table 1. AC line port bus voltage amplitude and phase angle difference before ring closure

In order to calculate the equivalent impedance of the port, first set the impedance of the Yuguanying-Nanyuan AC line to zero in the simulation calculation, and after closing the Yuguanying-Nanyuan double-circuit 220kV AC line, the active power flow is obtained:

ΔP ₀ =890.2MW,

The active closed-loop flow is basically equal to the closed-loop flow when the bus tie switch is used as the contact mode.

According to formula (10), it can be seen that for the Yuguanying-Nanyuan double-circuit 220kV AC line port, the equivalent impedance of the port is:

Therefore, the equivalent impedance of the AC line port and the bus tie switch port are basically the same.

According to the wiring relationship, it can be known that the reactance value of Yuguanying-Nanyuan double-circuit AC line is:

X _KK2 = 7.27Ω,

The tie line impedance is close to the port equivalent impedance. Therefore, according to the selection method of grid partition mutual supply and connection mode based on equivalent impedance, the AC line should be selected as the connection mode. At this time, the active power flow of the tie line mode is small.

Calculated by BPA, after closing the Yuguanying-Nanyuan double-circuit line, the current flow of active ring closure:

ΔP ₂ =462.4MW,

It can be seen that in this case, the active closed loop power flow when the AC line is used as the communication mode is obviously smaller than the corresponding value when the bus tie switch is used as the communication mode. Therefore, the method for selecting the interconnection mode of mutual supply and supply between power grid subregions provided by the present invention is effective.

The analysis of the above examples shows that this method overcomes the problems of diversity and arbitrariness in the existing selection methods of mutual supply and contact methods which lack a clear basis. The method for selecting the mutual supply and contact mode of the power grid partitions in the embodiment of the present invention is based on the principle of superposition, introducing the equivalent impedance of the port of the communication channel, decoupling the active and reactive parts of the closed-loop power flow, and according to the situation of the power grid where the communication channel is located, the According to the simplified analysis of the closed-loop power flow, according to the relationship between the tie line impedance and the equivalent impedance of the channel port, the selection method of the partition mutual supply and connection mode under the different system equivalent impedance is proposed, which provides a clear and reasonable selection of the mutual supply and connection mode. basis, thus improving the stability of the system.

It should be noted that the above-mentioned embodiments are only preferred embodiments of the present invention, and should not be understood as limiting the protection scope of the present invention. Any minor changes and modifications made to the present invention are acceptable without departing from the concept of the present invention. Belong to the protection scope of the present invention.

Claims (5)

1. a kind of sub-area division mutually supplies contact information system of selection, the method comprising the steps of:

The electrical network parameter of a, acquisition fault subregion and adjacent sectors；

B, determine the power shortage of fault subregion；

C, determine all interconnections of fault subregion mutually supply power；

Send passage whether fault under d, failure judgement subregion main transformer, if fault, close and mutually supply prominent interconnection as mutual For service channel, otherwise closure bus connection switch is as mutually supplying service channel；

E, judge whether to meet fault division power vacancy, if meeting execution step f, otherwise execution step g；

Whether f, judgement mutually transship for service channel, if overload, execution step g, and otherwise select contact information；

G, increase interconnection as mutually supplying service channel, execution step e；

In step b, determine that the power shortage of fault subregion is:

Wherein p_lossThere is the power loss in subregion during main transformer n-2 fault for fault subregion,

x_sfAnd x_ssFor other normal main transformers in subregion to compensation point equivalent impedance.

2. the sub-area division according to claim 1 mutually supplies contact information system of selection it is characterised in that in step a, obtaining Described fault subregion and the electrical network parameter of adjacent sectors is taken to include: to obtain the equivalent impedance of fault subregion and adjacent sectors.

3. the sub-area division according to claim 1 mutually supplies contact information system of selection it is characterised in that in step c, really Determine mutually including for power of all interconnections of fault subregion:

$p^{*}=\frac{1}{x_{\mathrm{\&sigma;}}^{*}}\mathrm{\&delta;}\mathrm{\&delta;},$

Wherein p^*For mutually supplying active power perunit value,

Mutually supply system equivalent impedance for contact,

δ δ is the phase angle change amount of fault subregion contact point.

4. the sub-area division according to claim 3 mutually supplies contact information system of selection it is characterised in that determining contact mutually For system equivalent impedanceIncluding:

C1, determine that two subregions are respectively as follows: to the equivalent impedance of contact point

x₁=jx_aj^tAnd x₂=kx_bk^t,

Wherein x_a、x_bFor distinguishing the nodal impedance matrix of two subregions,

Tie up row vector for m, j point is position in subregion a for the contact point, m is total nodes of subregion a；

Tie up row vector for n, k point is position in subregion b for the contact point, n is total nodes of subregion b；

C2, the impedance according to service channel itself the and two subregions equivalent impedance to contact point, determines that contact mutually supplies system Equivalent impedance.

5. the sub-area division according to claim 3 mutually supplies contact information system of selection it is characterised in that determining that fault is divided The phase angle change amount δ δ of area's contact includes:

δ δ=x^*p_δ ^*,

Wherein x^*For the perunit value of fault partitioned nodes impedance matrix,

p_δ ^*Vector for node injecting power variable quantity perunit value composition each under fault.