CN105449646A - Power distribution network electromagnetic looped network impedance analysis method - Google Patents

Abstract

The invention relates to a power distribution network electromagnetic looped network impedance analysis method. The method includes two steps which are carried out in sequence: establishment of a power distribution network electromagnetic looped network impedance model and determining of a power distribution network transmission current. The method provided by the invention establishes the power distribution network electromagnetic looped network impedance analysis method, can accurately calculate branch current distribution situations of the power distribution network, analyzes influence of the electromagnetic looped network on the normal operation and fault working conditions of the power distribution network, and facilitates reasonable arrangement and scientific utilization of an operation mode of the power distribution network electromagnetic looped network.

Description

A kind of power distribution network electromagnetic looped network Impedance method

Technical field

The present invention relates to a kind of analytic method of field of distribution network, specifically relate to a kind of power distribution network electromagnetic looped network Impedance method.

Background technology

In operation of power networks, electromagnetic looped network may cause part trend section transmission power limited, and the high-tension line light running of parallel running, suppressing portion divides circuit to give full play to ability to transmit electricity.If mishandling, electromagnetic looped network may cause power grid heat to stablize or transient stability destroys, thus jeopardizes electric power netting safe running.In operation of power networks process, the power outage that electromagnetic looped network causes is of common occurrence.At 500kV high-voltage fence first stage of construction, the stability disruption accident relevant with high and low pressure network configuration accounts for the ratio of whole accident up to 20%.In the repeatedly large-scale blackout occurred in the world, because electrical network exists electromagnetic looped network phenomenon in various degree, after ultra-high-tension power transmission line fault trip, a large amount of power flow transfer is to low-voltage circuit, cause many chain trippings of circuit overload, finally cause electric grid large area power cut, even electrical network is split as multiple islet operation.In order to avoid jeopardizing power grid security, the impact of electromagnetic looped network to be taken into full account when arranging power system operating mode, comprising: the stability of a system, power supply reliability, performance driving economy, and capacity of short circuit etc., take appropriate measures to reduce operation risk.

In some cases, reasonable arrangement and utilize electromagnetic looped network operational mode also to a certain degree can improve power distribution network utilance, reduce network loss etc.Such as, still not strong at the rack of high voltage order one level Grid first stage of construction, in order to ensure ability to transmit electricity, often select electromagnetic looped network operational mode.For power distribution network, reasonable arrangement high-and low-voltage circuit operation with closed ring mode can improve the power supply reliability of system, balanced low-voltage circuit trend distribution, thus reduces network loss.

At present, for electromagnetic looped network, carry out many research work, and achieved many achievements in research.Weak or the developing electrical network for rack, pays close attention to the impact how avoiding electromagnetic looped network on electricity net safety stable, comprising: unlink strategy and the risk analysis etc. of electromagnetic looped network.For the electrical network that structure comparison is strong, the emphasis of electromagnetic looped network research focuses mostly in suppression circulation or load disturbance distribution etc.Meanwhile, it is also the important directions that electromagnetic looped network is studied that steady-state economy runs, and comprises low-pressure side shunt influence, and high and low pressure side natural power is analyzed, electromagnetic looped network reactive circular power flow distribution etc.Along with society is to the raising of the requirement of energy efficiency and the quality of power supply, distributed energy (DistributedEnergyResources, DER) electrical network is accessed in a large number, modern active distribution network (ActiveDistributionNetwork, ADN) new requirement is proposed to the O&M of public power distribution network, meanwhile, it also promotes distribution network planning method for designing and runs control model to adjust accordingly.Operation with closed ring is the important operational mode of active distribution network, and in detail, accurate analytical method contributes to the analysis of the electromagnetic looped network operating mode of operation with closed ring power distribution network.

Summary of the invention

For the deficiencies in the prior art, the object of this invention is to provide a kind of power distribution network electromagnetic looped network Impedance method, electromagnetic looped network can be analyzed by the method and power distribution network normally be run and the impact of fault condition, analyze power distribution network electromagnetic loop-net operation mode.

The object of the invention is to adopt following technical proposals to realize:

The invention provides a kind of power distribution network electromagnetic looped network Impedance method, it is characterized in that, described method comprises: step (1) sets up power distribution network electromagnetic looped network impedance model; Power distribution network transmission current is determined with step (2).

Further, described step (1) comprising: set up power distribution network electromagnetic looped network Impedance model and power distribution network electromagnetic looped network Impedance low-pressure side circuit model.

Further, described power distribution network electromagnetic looped network Impedance model comprises: the branch road on the electromagnetic coupled path of electromagnetic looped network, electromagnetic looped network main ring and node, and the equivalent primary current of node;

Wherein node load electric current and the phasor sum flowing to line current outside path are the equivalent primary current of this node; The minimum ring comprising electromagnetic looped network electromagnetic coupled path is main ring; Power distribution network electromagnetic looped network Impedance model comprises: the branch road on the electromagnetic coupled path of electromagnetic looped network, electromagnetic looped network main ring and node, and the equivalent primary current of node; The Impedance electromagnetic looped network main ring of electromagnetic looped network.

Further, setting up power distribution network electromagnetic looped network Impedance low-pressure side circuit model is the impedance Mathematical Modeling extracting low-pressure side circuit from electromagnetic looped network two ends transformer low voltage side outlet.

Further, in described step (2), determine that power distribution network transmission current comprises: the calculating of main ring electric current and load current, the calculating of low-pressure side line current common current component, the calculating of current component of high-pressure side transmission and the calculating of electromagnetic looped network diverting coefficient;

The calculating of A, described main ring electric current and load current is respectively with comprising formula 1) to formula 5) represent:

Wherein: z ₁, z ₂, z ₃... z _nrespectively represent node 0 and 1,1 and 2,2 and 3 ... .n-1 the line impedance and between n; represent respectively node 1,2,3 ... .n main ring electric current, wherein, what regulation flowed into node is just, what flow out node is negative; represent respectively node 1,2,3 ... .n load current, wherein, what regulation flowed into node is just, what flow out node is negative;

By formula 1) referred to as:

$\mathrm{AI}=\left(\begin{array}{c}{I}_{\mathrm{LD}}\\ {\stackrel{\·}{V}}_0-{\stackrel{\·}{V}}_n\end{array}\right)---2);$

Wherein: formula 1) two matrixes on the equal sign left side are designated as A and I respectively, and the matrix on the right of equation is divided into two expression matrixs, and the first half is designated as matrix I, and last is designated as matrix A;

By formula 2) middle A matrix inversion:

Wherein: subscript i represents node serial number, scope is 1 to n;

Order:

$A^{-1}=\frac{1}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_i}\·\left(\begin{array}{cc}B& E\end{array}\right)---4);$

Wherein E is unit column vector, then:

$\begin{array}{c}I=\frac{1}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_i}\·\left(\begin{array}{cc}B& E\end{array}\right)\left(\begin{array}{c}{I}_{\mathrm{LD}}\\ {\stackrel{\·}{V}}_0-{\stackrel{\·}{V}}_n\end{array}\right)\\ =\frac{1}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_i}\·{\mathrm{BI}}_{\mathrm{LD}}+\frac{{\stackrel{\·}{V}}_0-{\stackrel{\·}{V}}_n}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_i}\·E\end{array}---5);$

Formula 5) column vector for being made up of low-pressure side line current on the left of equal sign, the Section 1 on the right side of last equal sign is node equivalent primary current current component on the line, and Section 2 is constant and unit column vector product;

The calculating of B, low-pressure side line current common current component comprises:

All low-pressure side line currents all have a common current component; This current component be path both end voltage difference with path impedance and ratio, reflect the current component by this line transmission; Suppose that transformer voltage ratio is k, low-pressure side i-th branch impedance is designated as z _iL, by this current component reduction to high-pressure side:

${\stackrel{\·}{I}}_{\text{L}}^H=\frac{{\stackrel{\·}{V}}_A-{\stackrel{\·}{V}}_B}{k^2\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_{\mathrm{iL}}}---6);$

Wherein: expression 5) part on the right of equation above Section 1 score line, expression 5) part on the right of equation above Section 2 score line, its physical significance is the matrix of node voltage composition;

The calculating of the current component of C, high-pressure side transmission comprises:

The branch impedance of i-th, high-pressure side is designated as z _iH, the current component transmitted by high-pressure side is:

${\stackrel{\·}{I}}_H=\frac{{\stackrel{\·}{V}}_A-{\stackrel{\·}{V}}_B}{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{z}_{\mathrm{iH}}}---7);$

The calculating of D, electromagnetic looped network diverting coefficient comprises:

Definition electromagnetic looped network diverting coefficient is:

$\mathrm{\β}=\frac{{\stackrel{\·}{I}}_L^H}{{\stackrel{\·}{I}}_H}=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{z}_{\mathrm{iH}}}{k^2\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_{\mathrm{iL}}}---8);$

Referred to as:

$\mathrm{\β}=\frac{z_H}{k^2\·z_L}---9);$

Wherein: z _hrepresent all branch impedances in high-pressure side and; z _lrepresent low-pressure side all branch impedances and.

Further, the parsing of power distribution network electromagnetic looped network impedance comprises the parsing of the parsing of the electromagnetic looped network impedance of accidental conditions and the electromagnetic looped network impedance of accident operating condition.

Further, the parsing of the electromagnetic looped network impedance of accidental conditions comprises:

(1) all branch impedance sum z in high-pressure side _hduring → ∞, β is maximum for electromagnetic looped network diverting coefficient, that is:

$\mathrm{\β}=\underset{z_H\→\∞}{\lim }\frac{z_H}{k^2\·z_L}---10);$

High-pressure side branch road by electromagnetic looped network be diverted to the electric current of low-pressure side branch road maximum time, the impact of electromagnetic looped network on low-pressure side Branch Power Flow is the most serious;

(2) all branch impedance sum z of low-pressure side _lduring → ∞, electromagnetic looped network diverting coefficient β=0, namely the branch road electric current that is diverted to low-pressure side branch road by electromagnetic looped network in high-pressure side is minimum, and the impact of electromagnetic looped network on low-pressure side Branch Power Flow is minimum; Now, the through-put power on low-pressure side branch road is the own power of low-pressure side load;

(3) when all branch impedance sums in high-pressure side are determined, and all branch impedances of low-pressure side and be z _ltime ∈ (0, ∞), electromagnetic looped network diverting coefficient β and all branch impedances of low-pressure side and z _lclosely related, namely low-pressure side all branch impedances sum is less, and the impact of electromagnetic looped network on low-pressure side Branch Power Flow is larger; Otherwise, all branch impedance sum z of low-pressure side _llarger, the impact of electromagnetic looped network on low-pressure side Branch Power Flow is less;

When power distribution network adopts operation with closed ring mode, under accidental conditions, low-pressure side circuit can not transship because of operation with closed ring, and high-pressure side circuit will cause transmission power significantly to reduce because of forming electromagnetic looped network with low-pressure side circuit.

Further, the electromagnetic looped network Impedance of accident operating condition comprises:

Under the electromagnetic looped network ruuning situation of high-pressure side, when any high-pressure side circuit is out of service because of fault, and high-pressure side electromagnetic looped network by All other routes still keep be communicated with time, electromagnetic looped network diverting coefficient β is 0.01, and medium voltage distribution network normally runs unaffected;

Under extreme accident operating condition, if many high-tension lines because of fault out of service, destroy the connectedness of high-voltage electromagnetic looped network, now, all branch impedances in high-pressure side and z _h→ ∞, then electromagnetic looped network diverting coefficient β reaches maximum, and the trend of former high-pressure side circuit transfers to medium voltage side circuit in a large number, causes medium voltage side circuit overload; Now, disconnect medium voltage side electromagnetic looped network, avoid the electric current of medium voltage side power distribution network sharply to increase, cause protection act and the loop dead electricity at medium voltage side circuit two ends.

Compared with the prior art, the beneficial effect that the present invention reaches is:

The present invention sets up power distribution network electromagnetic looped network Impedance model (1) accurately can calculate each branch current distribution situation of power distribution network; (2) impact that normally runs power distribution network of quantitative analysis electromagnetic looped network, is conducive to reasonable arrangement and scientific utilization power distribution network electromagnetic loop-net operation mode; (3) quantitative analysis electromagnetic looped network is on the impact of distribution network failure operating mode, is conducive to arranging defencive function targetedly, takes counter-measure; (4) for the selection of Distribution Network Equipment type selecting and device parameter provides reference data; (5) for power distribution network economic security operation study provides technical support.

Accompanying drawing explanation

Fig. 1 is the Impedance model schematic of electromagnetic looped network provided by the invention;

Fig. 2 is that low-pressure side line impedance provided by the invention resolves schematic diagram;

Fig. 3 is the flow chart of power distribution network electromagnetic looped network Impedance method provided by the invention;

Fig. 4 is that high voltage distribution network provided by the invention breaks down and prepares tripping circuit both sides switch schematic diagrames.

Embodiment

Below in conjunction with accompanying drawing, the specific embodiment of the present invention is described in further detail.

The invention provides a kind of power distribution network electromagnetic looped network Impedance method, flow chart as shown in Figure 3, comprise carry out successively set up power distribution network electromagnetic looped network impedance model and determine power distribution network transmission current two steps.

One, set up power distribution network electromagnetic looped network impedance model to comprise: set up power distribution network electromagnetic looped network Impedance basic model and set up power distribution network electromagnetic looped network Impedance low-pressure side circuit model;

Set up power distribution network electromagnetic looped network Impedance basic model as shown in Figure 1.Power distribution network electromagnetic looped network Impedance basic model comprises: the branch road on the electromagnetic coupled path of electromagnetic looped network, electromagnetic looped network main ring and node, and the equivalent primary current of each node; Wherein: the phasor sum of setting each node load electric current (flow out the sense of current as just) and flowing to line current outside path is called the equivalent primary current of this node; The minimum ring comprising electromagnetic looped network electromagnetic coupled path is called main ring.The branch road on the electromagnetic coupled path of electromagnetic looped network, electromagnetic looped network main ring and node is comprised in Impedance model shown in basic model Fig. 4, and the equivalent primary current etc. of each node.The Impedance of electromagnetic looped network only carries out for main ring.

Described power distribution network electromagnetic looped network Impedance low-pressure side circuit model of setting up extracts low-pressure side circuit model from electromagnetic looped network two ends transformer low voltage side outlet, as shown in Figure 2.

Two, determine that power distribution network transmission current comprises: main ring electric current and load current calculate, and low-pressure side line current common current component calculates, the current component transmitted by high-pressure side is calculated and electromagnetic looped network diverting coefficient calculates;

A, described main ring electric current and load current calculate respectively with comprising formula 1) to formula 5) represent:

The relation of main ring electric current and load current is such as formula 1) shown in:

Wherein: wherein: z ₁, z ₂, z ₃... z _nrespectively represent node 0 and 1,1 and 2,2 and 3 ... .n-1 the line impedance and between n; represent respectively node 1,2,3 ... .n main ring electric current, wherein, what regulation flowed into node is just, what flow out node is negative; represent respectively node 1,2,3 ... .n load current, wherein, what regulation flowed into node is just, what flow out node is negative.

Referred to as:

$\mathrm{AI}=\left(\begin{array}{c}{I}_{\mathrm{LD}}\\ {\stackrel{\·}{V}}_0-{\stackrel{\·}{V}}_n\end{array}\right)---2);$

Wherein: formula 1) two matrixes on the equal sign left side are designated as A and I respectively, and the matrix on the right of equation is divided into two expression matrixs, and the first half is designated as matrix I, and last is designated as matrix A;

By formula 2) middle A matrix inversion:

Wherein: subscript i represents node serial number, scope is 1 to n;

Order:

$A^{-1}=\frac{1}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_i}\·\left(\begin{array}{cc}B& E\end{array}\right)---4);$

Wherein E is unit column vector, then:

$\begin{array}{c}I=\frac{1}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_i}\·\left(\begin{array}{cc}B& E\end{array}\right)\left(\begin{array}{c}{I}_{\mathrm{LD}}\\ {\stackrel{\·}{V}}_0-{\stackrel{\·}{V}}_n\end{array}\right)\\ =\frac{1}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_i}\·{\mathrm{BI}}_{\mathrm{LD}}+\frac{{\stackrel{\·}{V}}_0-{\stackrel{\·}{V}}_n}{\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_i}\·E\end{array}---5);$

Formula 5) column vector for being made up of low-pressure side line current on the left of first equal sign, the Section 1 on the right side of last equal sign is node equivalent primary current current component on the line, and Section 2 is constant and unit column vector product;

B, low-pressure side line current common current component calculate and comprise:

All low-pressure side line currents all have a common current component; This current component be path both end voltage difference with path impedance and ratio, reflect the current component by this line transmission; Suppose that transformer voltage ratio is k, low-pressure side i-th branch impedance is designated as z _iL, by this current component reduction to high-pressure side:

${\stackrel{\·}{I}}_{\text{L}}^H=\frac{{\stackrel{\·}{V}}_A-{\stackrel{\·}{V}}_B}{k^2\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_{\mathrm{iL}}}---6);$

Wherein: expression 5) part on the right of equation above Section 1 score line, expression 5) part on the right of equation above Section 2 score line, its physical significance is the matrix of node voltage composition.

C, the current component transmitted by high-pressure side are calculated and comprise:

The branch impedance of i-th, high-pressure side is designated as z _iH, the current component transmitted by high-pressure side is:

${\stackrel{\·}{I}}_H=\frac{{\stackrel{\·}{V}}_A-{\stackrel{\·}{V}}_B}{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{z}_{\mathrm{iH}}}---7);$

D, electromagnetic looped network diverting coefficient calculate and comprise:

Definition electromagnetic looped network diverting coefficient is:

$\mathrm{\β}=\frac{{\stackrel{\·}{I}}_L^H}{{\stackrel{\·}{I}}_H}=\frac{\underset{i=1}{\overset{m}{\mathrm{\Σ}}}{z}_{\mathrm{iH}}}{k^2\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{z}_{\mathrm{iL}}}---8);$

Referred to as:

$\mathrm{\β}=\frac{z_H}{k^2\·z_L}---9);$

Wherein: z _hrepresent all branch impedances in high-pressure side and; z _lrepresent low-pressure side all branch impedances and.

Electromagnetic looped network diverting coefficient describes the ratio of parallel line through-put power, and the reflection low-pressure side of electromagnetic looped network and high-pressure side parallel shunt are transmitted electricity effect.According to formula 9) known, the diverting coefficient of electromagnetic looped network and the impedance of high and low pressure branch road and ratio closely related, have nothing to do with the payload of high and low pressure side and distribute.

Embodiment

Below in conjunction with specific embodiment, technical scheme of the present invention is described in further detail.

The electromagnetic looped network Impedance of accidental conditions and the electromagnetic looped network Impedance of accident operating condition is comprised during power distribution network electromagnetic looped network Impedance.

1, accidental conditions analysis:

(1) as high pressure branch impedance and z _hduring → ∞, diverting coefficient β is maximum, namely

$\mathrm{\β}=\underset{z_H\→\∞}{\lim }\frac{z_H}{k^2\·z_L}---10);$

Now, the electric current that high-pressure side branch road is diverted to low-pressure side branch road by electromagnetic looped network is maximum, and the impact of electromagnetic looped network on low-pressure side Branch Power Flow is also the most serious.

(2) as low-pressure side branch impedance and z _lduring → ∞, diverting coefficient β=0, namely the high pressure branch road electric current that is diverted to low pressure branch road by electromagnetic looped network is minimum, and electromagnetic looped network is also minimum on the impact of low pressure Branch Power Flow.Now, the through-put power on low pressure branch road is low-voltage load own power.

(3) when high-pressure side branch impedance with determine, and low-pressure side branch impedance and be z _ltime ∈ (0, ∞), diverting coefficient β and low-pressure side impedance sum z _lclosely related.Low-pressure side impedance sum is less, and the impact of electromagnetic looped network on low pressure Branch Power Flow is larger.Otherwise, low-pressure side impedance sum z _llarger, the impact of electromagnetic looped network on low pressure Branch Power Flow is less.

From formula 9), the maximum of diverting coefficient β depends on high pressure branch impedance, transformer voltage ratio and low pressure branch impedance.For power transmission network, because the impedance perunit value of different electric pressure (such as 500kV/220kV) circuit is close, transformer voltage ratio is less (about about 2 times) also, and therefore, the maximum of diverting coefficient β is larger.During normal operation, the impact of electromagnetic looped network on system cloud gray model is larger.Compared with high-tension line, the resistance value of the low-pressure side circuit of power distribution network is large, and high and low pressure electric pressure differs greatly, and transformer voltage ratio large (about about 10 times), the maximum of diverting coefficient β is less.For the electromagnetic looped network that 110kV high voltage distribution network and 10kV medium voltage distribution network are formed, generally,

$\left\{\begin{array}{c}{k}^2>10\×10\\ z_L>z_H\end{array}\right.---11);$

Now, the span of diverting coefficient β is (0,0.01), and when normally running, the shunting action of electromagnetic looped network to high-tension line is little.

More than analyze known, when power distribution network adopts operation with closed ring mode, under normal operating conditions, low-voltage circuit can not transship because of operation with closed ring, and high-tension line also will cause transmission power significantly to reduce because of forming electromagnetic looped network with low-voltage circuit.

2, accident operating condition analysis:

For the electromagnetic looped network that 110kV high voltage distribution network and 10kV medium voltage distribution network are formed, in the loop-net operation situation of high-pressure side, when any high-tension line is out of service because of fault, and high-pressure side looped network by All other routes still keep be communicated with time, diverting coefficient β is about 0.01, and medium voltage distribution network normally runs substantially unaffected.

But, in extreme circumstances, if many high-tension lines because of fault out of service, destroy the connectedness of high pressure ring, now, high pressure branch impedance and z _h→ ∞, then diverting coefficient β reaches maximum, and the trend of former high-tension line transfers to medium-voltage line in a large number, causes medium-voltage line to transship.Now, consider from the angle of electric power netting safe running, must responsible measures be taked, pressure ring net in disconnection, avoid the electric current of medium voltage distribution network sharply to increase, cause protection act and the loop dead electricity at medium-voltage line two ends.

3, " cut off-excise " Fault Control technical Analysis:

Take " cutting off-excision " chain loop network control technology of cut-offfing can prevent above-mentioned phenomenon from occurring.This technology is divided into two steps: the first step first unties the medium-voltage distribution mesh portions of electromagnetic looped network, and second step is excision fault high-tension line.After the operation of the execution first step, because electromagnetic looped network is destroyed, low-pressure side branch impedance and z _l→ ∞, diverting coefficient β=0, low pressure branch road only transmits low-voltage load own power, no longer transmits other power.After second step excision fault high-tension line, because electromagnetic looped network is destroyed, high-voltage transmission power can not be there is again and shift in a large number to low-voltage circuit, thus cause low-pressure side circuit overload trip phenomenon.Therefore, this method significantly can reduce the load loss of medium voltage distribution network.

For Fig. 4, high voltage distribution network in electromagnetic looped network breaks down and prepares tripping circuit both sides switch (as A and B in Fig. 4) before causing electromagnetic looped network to unlink, according to trend and load optimal principle, first the intelligent switch (as intelligent switch in Fig. 4) in the middle of medium voltage side closed loop is disconnected, realize first carrying out electromagnetic looped network from medium voltage distribution network to unlink, and make every effort to the load balance as far as possible of the both sides feeder line after open loop operation, can two schemes be taked.

(1) two intelligent switch uncoupling loop scheme.When electromagnetic looped network unlinks, system sends trip command, to reduce load loss as far as possible to two adjacent intelligent switchs simultaneously.

(2) two configuration intelligent switch scheme.Needs carry out magnet ring net unlink time, according to load balancing principle, some two configuration intelligent switchs in the medium voltage distribution network of tripping operation with closed ring, and the circuit of tripping simultaneously.

Power distribution network Impedance model provided by the invention and computational methods, can analyze electromagnetic looped network and normally run power distribution network and the impact of fault condition, analyzes power distribution network electromagnetic loop-net operation mode.Power distribution network electromagnetic loop-net operation mode affects distribution line to a certain extent and gives full play to ability to transmit electricity, but, reasonable arrangement and utilize electromagnetic looped network operational mode also to a certain degree can improve power distribution network utilance, reduce network loss etc.The power distribution network of loop design will form multi-form high and low pressure electromagnetic looped network when operation with closed ring mode, and obvious with power transmission network electromagnetic looped network difference.Adopt Impedance method first, set up power distribution network electromagnetic looped network Impedance model, accurately can calculate each branch current distribution situation of power distribution network, analyze electromagnetic looped network and power distribution network is normally run and the impact of fault condition, and propose the scheme controlling fault effects.Above-mentioned achievement in research is conducive to reasonable arrangement and scientific utilization power distribution network electromagnetic loop-net operation mode.

Finally should be noted that: above embodiment is only in order to illustrate that technical scheme of the present invention is not intended to limit, although with reference to above-described embodiment to invention has been detailed description, those of ordinary skill in the field are to be understood that: still can modify to the specific embodiment of the present invention or equivalent replacement, and not departing from any amendment of spirit and scope of the invention or equivalent replacement, it all should be encompassed in the middle of right of the present invention.

Claims (8)

1. a power distribution network electromagnetic looped network Impedance method, is characterized in that, described method comprises: step (1) sets up power distribution network electromagnetic looped network impedance model; Power distribution network transmission current is determined with step (2).

2. power distribution network electromagnetic looped network Impedance method as claimed in claim 1, it is characterized in that, described step (1) comprising: set up power distribution network electromagnetic looped network Impedance model and power distribution network electromagnetic looped network Impedance low-pressure side circuit model.

3. power distribution network electromagnetic looped network Impedance method as claimed in claim 2, it is characterized in that, described power distribution network electromagnetic looped network Impedance model comprises: the branch road on the electromagnetic coupled path of electromagnetic looped network, electromagnetic looped network main ring and node, and the equivalent primary current of node;

Wherein node load electric current and the phasor sum flowing to line current outside path are the equivalent primary current of this node; The minimum ring comprising electromagnetic looped network electromagnetic coupled path is main ring; Power distribution network electromagnetic looped network Impedance model comprises: the branch road on the electromagnetic coupled path of electromagnetic looped network, electromagnetic looped network main ring and node, and the equivalent primary current of node; The Impedance electromagnetic looped network main ring of electromagnetic looped network.

4. power distribution network electromagnetic looped network Impedance method as claimed in claim 2, is characterized in that, setting up power distribution network electromagnetic looped network Impedance low-pressure side circuit model is the impedance Mathematical Modeling extracting low-pressure side circuit from electromagnetic looped network two ends transformer low voltage side outlet.

5. power distribution network electromagnetic looped network Impedance method as claimed in claim 1, it is characterized in that, in described step (2), determine that power distribution network transmission current comprises: the calculating of main ring electric current and load current, the calculating of low-pressure side line current common current component, the calculating of current component of high-pressure side transmission and the calculating of electromagnetic looped network diverting coefficient;

The calculating of A, described main ring electric current and load current is respectively with comprising formula 1) to formula 5) represent:

Wherein: z ₁, z ₂, z ₃z _nrespectively represent node 0 and 1,1 and 2,2 and 3 ... .n-1 the line impedance and between n; represent respectively node 1,2, the main ring electric current of 3 ... .n, wherein, what regulation flowed into node just be, outflow node be negative; represent respectively node 1,2, the load current of 3 ... .n, wherein, what regulation flowed into node just be, outflow node be negative;

By formula 1) referred to as:

Wherein: formula 1) two matrixes on the equal sign left side are designated as A and I respectively, and the matrix on the right of equation is divided into two expression matrixs, and the first half is designated as matrix I, and last is designated as matrix A;

By formula 2) middle A matrix inversion:

Wherein: subscript i represents node serial number, scope is 1 to n;

Order:

Wherein E is unit column vector, then:

Formula 5) column vector for being made up of low-pressure side line current on the left of equal sign, the Section 1 on the right side of last equal sign is node equivalent primary current current component on the line, and Section 2 is constant and unit column vector product;

The calculating of B, low-pressure side line current common current component comprises:

All low-pressure side line currents all have a common current component; This current component be path both end voltage difference with path impedance and ratio, reflect the current component by this line transmission; Suppose that transformer voltage ratio is k, low-pressure side i-th branch impedance is designated as z _iL, by this current component reduction to high-pressure side:

Wherein: expression 5) part on the right of equation above Section 1 score line, expression 5) part on the right of equation above Section 2 score line, its physical significance is the matrix of node voltage composition;

The calculating of the current component of C, high-pressure side transmission comprises:

The branch impedance of i-th, high-pressure side is designated as z _iH, the current component transmitted by high-pressure side is:

The calculating of D, electromagnetic looped network diverting coefficient comprises:

Definition electromagnetic looped network diverting coefficient is:

Referred to as:

Wherein: z _hrepresent all branch impedances in high-pressure side and; z _lrepresent low-pressure side all branch impedances and.

6. power distribution network electromagnetic looped network Impedance method as claimed in claim 1, it is characterized in that, the parsing of power distribution network electromagnetic looped network impedance comprises the parsing of the parsing of the electromagnetic looped network impedance of accidental conditions and the electromagnetic looped network impedance of accident operating condition.

7. power distribution network electromagnetic looped network Impedance method as claimed in claim 6, it is characterized in that, the parsing of the electromagnetic looped network impedance of accidental conditions comprises:

(1) all branch impedance sum z in high-pressure side _hduring → ∞, β is maximum for electromagnetic looped network diverting coefficient, that is:

High-pressure side branch road by electromagnetic looped network be diverted to the electric current of low-pressure side branch road maximum time, the impact of electromagnetic looped network on low-pressure side Branch Power Flow is the most serious;

(2) all branch impedance sum z of low-pressure side _lduring → ∞, electromagnetic looped network diverting coefficient β=0, namely the branch road electric current that is diverted to low-pressure side branch road by electromagnetic looped network in high-pressure side is minimum, and the impact of electromagnetic looped network on low-pressure side Branch Power Flow is minimum; Now, the through-put power on low-pressure side branch road is the own power of low-pressure side load;

(3) when all branch impedance sums in high-pressure side are determined, and all branch impedances of low-pressure side and be z _ltime ∈ (0, ∞), electromagnetic looped network diverting coefficient β and all branch impedances of low-pressure side and z _lclosely related, namely low-pressure side all branch impedances sum is less, and the impact of electromagnetic looped network on low-pressure side Branch Power Flow is larger; Otherwise, all branch impedance sum z of low-pressure side _llarger, the impact of electromagnetic looped network on low-pressure side Branch Power Flow is less;

When power distribution network adopts operation with closed ring mode, under accidental conditions, low-pressure side circuit can not transship because of operation with closed ring, and high-pressure side circuit will cause transmission power significantly to reduce because of forming electromagnetic looped network with low-pressure side circuit.

8. power distribution network electromagnetic looped network Impedance method as claimed in claim 6, it is characterized in that, the electromagnetic looped network Impedance of accident operating condition comprises:

Under the electromagnetic looped network ruuning situation of high-pressure side, when any high-pressure side circuit is out of service because of fault, and high-pressure side electromagnetic looped network by All other routes still keep be communicated with time, electromagnetic looped network diverting coefficient β is 0.01, and medium voltage distribution network normally runs unaffected;

Under extreme accident operating condition, if many high-tension lines because of fault out of service, destroy the connectedness of high-voltage electromagnetic looped network, now, all branch impedances in high-pressure side and z _h→ ∞, then electromagnetic looped network diverting coefficient β reaches maximum, and the trend of former high-pressure side circuit transfers to medium voltage side circuit in a large number, causes medium voltage side circuit overload; Now, disconnect medium voltage side electromagnetic looped network, avoid the electric current of medium voltage side power distribution network sharply to increase, cause protection act and the loop dead electricity at medium voltage side circuit two ends.