CN103280841A - On-grid point confirmation method for intermittent energy sources - Google Patents

Abstract

The invention discloses an on-grid point confirmation method for intermittent energy sources, and belongs to the technical field of electrical power system control. According to the on-grid point confirmation method for the intermittent energy sources, the power flow entropies of a power grid when the intermittent energy sources are accessed to the power grid from different access points are used as measurement indicators, the malconformation of the line power flow is analyzed quantitatively, the access point which enables the power flow entropy of the power grid to be the smallest is used as the optimized on-grid point for the intermittent energy sources, and thus the impact on the power grid after the intermittent energy sources are connected to the power grid is the minimum. At the same time, the existing power flow entropy models are improved, a load ratio is introduced and is used as a penalty coefficient of the power flow entropy, and the impact on the power grid system of the power flow change is reflected accurately.

Description

Method is determined in a kind of also site of intermittent energy source

Technical field

Method is determined in the also site that the present invention relates to a kind of intermittent energy source, belongs to the control technique in power system field.

Background technology

Be that the regenerative resource of representative has characteristics such as intermittence, randomness and uncertainty with wind-force, photovoltaic generation.Along with the regenerative resource permeability constantly increases, they have brought increasing challenge for the safe and reliable operation of electrical network.A series of stabilization of power grids problems such as brought that voltage is stable, frequency stabilization and circuit through-put power are out-of-limit.The wind energy turbine set scale is incorporated into the power networks may influence the reliability of power system operation.Therefore, need planning of science activities and the scale and the operational mode that design wind energy turbine set, take into full account factors such as the restriction of grid structure and ability to transmit electricity thereof and power equipment random fault.Lot of domestic and international research at present all concentrates on and inserts the power distribution network on-site elimination, and intermittent energy source concentrates the operation control research that inserts the voltage levels power transmission network just at the early-stage both at home and abroad, and the research of intermittent energy source and Selection of Net Points is fewer.

Document " based on the complex electric network self-organizing critical state judgment models of trend entropy " has proposed the concept of electric network swim entropy based on entropy theory, the lack of uniformity that distributes in order to quantitative description circuit trend.It has been divided into many minizones with load factor, and to the number of lines randomization in the different loads rate interval, and then has used the formula of entropy.

It is identical that common trend entropy formula has implied the status of each probability interval, and analyzed the confusion degree of system load rate on this basis.It is different to the influence degree of system that yet load factor is in different intervals.Load factor μ _i(1 ,+extent of injury ∞) is obviously than μ for ∈ _i∈ (0,1) is big, and load factor to depart from (0,1) interval more far away, the extent of injury is more big, is necessary this situation is done some processing.

Summary of the invention

Technical problem to be solved by this invention is to overcome the prior art deficiency, provide a kind of also site of intermittent energy source to determine method, utilize and improve the trend entropy as measurement index, from to be selected and site, select optimum and site, the feasible harmful effect minimum of back trend fluctuation to network system that be incorporated into the power networks.

The present invention solves the problems of the technologies described above by the following technical solutions:

Method is determined in a kind of also site of intermittent energy source, is used for selecting optimum also site from a plurality of optional intermittent energy source of electrical network and site; The improvement trend entropy of described electrical network when calculating described intermittent energy source and inserting each optional intermittent energy source and site respectively, and select to make electrical network improvement trend entropy minimum and the site as optimum and the site; The improvement trend entropy of described electrical network calculates according to following formula:

$\tilde{H}=-C\underset{i}{\mathrm{\Σ}}{a}_i{p}_i\ln p_i,$

Wherein,

Expression improves the trend entropy; C is constant; p _iThe interval U of expression load factor _iIn the circuit number account for the ratio of grid bus way; a _iBe the interval U of load factor _iTrend entropy penalty coefficient, determine according to following formula:

$a_i=\left\{\begin{array}{cc}1,& 0\≤{\mathrm{\μ}}_{i,\mathrm{mid}}\≤1\\ {\stackrel{\‾}{\mathrm{\μ}}}_i,& {\mathrm{\μ}}_{i,\mathrm{mid}}>1\end{array}\right.,$

Wherein, μ _{I, mid}Be the interval U of load factor _iMidrange;

Be the interval U of load factor _iIn the mean value of each line load rate.

The present invention improves existing trend entropy model, introduces load factor as the penalty coefficient of trend entropy, though distribute orderly and out-of-limit circuit more for a long time when trend, the value of trend entropy is still very big; Have only when trend both to distribute orderly and out-of-limit number of lines more after a little while, the value of trend entropy just can reduce, and has reflected that more accurately trend changes the influence to network system; The present invention so with improved trend entropy as measurement index, to be selected and site, select to make electrical network improvement trend entropy minimum and the site, thereby make the harmful effect minimum of back trend fluctuation to network system that be incorporated into the power networks.

Description of drawings

Fig. 1 is IEEE39 node system winding diagram in the l-G simulation test.

Embodiment

Below in conjunction with accompanying drawing technical scheme of the present invention is elaborated:

Thinking of the present invention is that the trend entropy of electrical network when inserting from different access points with intermittent energy source is as measurement index, the lack of uniformity of quantitative analysis circuit trend, selection makes the access point of electric network swim entropy minimum as intermittent energy source and the site of optimum, thereby makes intermittent energy source the influence minimum of back to electrical network that be incorporated into the power networks; Simultaneously, existing trend entropy model is improved, introduce load factor as the penalty coefficient of trend entropy, reflected that more accurately trend changes the influence to network system.

For the ease of the public understanding technical solution of the present invention, below earlier the substance of existing trend entropy is briefly introduced.

If the meritorious transmission capacity of the maximum of circuit i is

The actual trend of circuit i was P when system moved _i, the load factor μ of circuit i then _iFor:

${\mathrm{\&mu;}}_i=\left|\frac{P_i}{P_i^{\max }}\right|i=\mathrm{1,2},\&CenterDot;\&CenterDot;\&CenterDot;,{\mathrm{<figure-callout\; id="1"\; label="N"\; filenames="130621094630.png"\; state="\{\{state\}\}">N</figure-callout>}}_1$

In the formula: N ₁Be the circuit number.

In order to describe the balanced intensity of circuit trend, we must divide the load factor interval.The step-length of given load factor siding-to-siding block length is Δ U, thus all load factor intervals can be expressed as ((k-1) Δ U, k Δ U] (k ∈ Z), the load factor scope of the concrete value set of k during according to system's actual motion determined.If k ∈ is { k ₁, k ₂..., k _n(n is the number in load factor interval).This n load factor interval is designated as U respectively ₁, U ₂..., U _nUse l _kExpression load factor μ _i∈ U _kThe number of lines, the number of lines randomization in the different loads rate interval is got:

$p_k=\frac{l_k}{\underset{j=1}{\overset{n}{\mathrm{\&Sigma;}}}{l}_j}$

So can get the electric network swim entropy be:

$H=-C\underset{i}{\mathrm{\&Sigma;}}{p}_i\ln p_i$

The status that above-mentioned trend entropy formula has implied each probability interval is identical, and has analyzed the confusion degree of system on this basis.It is different to the influence degree of system that yet load factor is in different intervals.Load factor μ _i(1 ,+extent of injury ∞) is obviously than μ for ∈ _i∈ (0,1) is big, and load factor to depart from (0,1) interval more far away, the extent of injury is more big, is necessary this situation is done some processing.The status in load factor interval is the same in the present invention's supposition [0,1], (1 ,+∞) status in middle load factor interval is dull rises.

Therefore, trend entropy formula just can be modified to:

$\tilde{H}=-C\underset{i}{\mathrm{\&Sigma;}}{a}_i{p}_i\ln p_i$

Wherein,

Expression improves the trend entropy; C is constant; p _iThe interval U of expression load factor _iIn the circuit number account for the ratio of grid bus way; a _iBe the interval U of load factor _iTrend entropy penalty coefficient, determine according to following formula:

$a_i=\left\{\begin{array}{cc}1,& 0\&le;{\mathrm{\&mu;}}_{i,\mathrm{mid}}\&le;1\\ {\stackrel{\&OverBar;}{\mathrm{\&mu;}}}_i,& {\mathrm{\&mu;}}_{i,\mathrm{mid}}>1\end{array}\right.,$

Wherein, μ _{I, mid}Be the interval U of load factor _iMidrange;

Be the interval U of load factor _iIn the mean value of each line load rate.

Here introduce load factor as the penalty coefficient of trend entropy, though distribute orderly and out-of-limit circuit more for a long time when trend, the value of trend entropy is still very big; Have only when trend both to distribute orderly and out-of-limit number of lines more after a little while, the value of trend entropy just can reduce.Therefore, load factor is introduced in the trend distributional analysis that intermittent energy source is incorporated into the power networks, can effectively be remedied the deficiency of common trend entropy, reasonably analyze the operation conditions that intermittent energy source inserts the back system.

Utilize above-mentioned improvement trend entropy model as evaluation index, can from optional intermittent energy source and site, select to the systematic influence minimum improvement trend entropy minimum of electrical network (namely make) and the site, for example can adopt following method:

Insert the intermittent energy source (for example wind energy turbine set, photovoltaic electric field, morning and evening tides electric field etc.) of identical scale from a plurality of and site to be selected respectively and carry out emulation (for example adopting Monte Carlo simulation method commonly used), and utilize above-mentioned improvement trend entropy formula to calculate, obtain intermittent energy source from be incorporated into the power networks a some improvement trend entropy of electrical network when inserting of difference.The size of improving trend entropy numerical value has reflected that intermittent energy source inserts the back to the influence degree of system, the value of improving the trend entropy is more little, and trend distributes just more balanced, and the out-of-limit degree of trend is just more little, system is suffered influences minimum, and namely numerical value is more little more favourable to system.Therefore, choosing the node that improves trend entropy minimum is intermittent energy source and site.

In order to verify effect of the present invention, be example with New England 10 machines, 39 node test systems, this method is carried out simulating, verifying, system wiring figure sees Fig. 1.Suppose that node 30,32～39 is intermittent energy source and site to be selected.Inserting installed capacity at these nodes successively is that the wind energy turbine set of 2.0pu is with the conventional unit of replacement same capability.Simulated conditions is as follows: 1) wind speed of wind energy turbine set satisfies that scale parameter is 9.0, form parameter is that 2.15 two-parameter Weibull distributes; 2) wind energy turbine set adopts the constant voltage control strategy; 3) Fu He random fluctuation Normal Distribution, wherein load is meritorious and idle is desired value with the original system data respectively, standard deviation is 10% of desired value.

Insert wind energy turbine set at wind farm grid-connected node above-mentioned to be selected respectively, calculate mean value, variance, maximum and the minimum value of the improvement trend entropy of electrical network, common trend entropy, risk index, list in table 1, table 2, table 3 respectively.

Table 1 wind energy turbine set inserts the improvement trend entropy of different nodes

Table 2 wind energy turbine set inserts the common trend entropy of different nodes

Table 3 wind energy turbine set inserts the risk index of different nodes

Risk Theory is the uncertain factor of taking into account system, the theory that will cause the severity of the possibility of disaster and this disaster to combine.The factor of the possibility of the risk indicator assurance accident quantitatively of electric power system and these 2 decision systems reliabilities of seriousness, thus reflection accident more all sidedly is to the influence of whole electric power system.

The distribution situation difference of the trend of different time section for the out-of-limit degree of risk of quantitative response trend, supposes that when trend was not out-of-limit, seriousness was 0, and when out-of-limit, seriousness is corresponding load factor.Therefore, the out-of-limit risk index of definition trend is:

$\mathrm{Risk}=\underset{i\&Element;{\mathrm{\&Omega;}}_{\mathrm{over}}}{\mathrm{\&Sigma;}}{\mathrm{\&mu;}}_i{p}_i$

In the formula: Ω _OverSet for out-of-limit circuit.

Following formula has reflected the degree of risk that trend is out-of-limit, and when out-of-limit number of lines is more many, out-of-limit degree is more big, and risk index is more big; When not having circuit out-of-limit, risk index is zero.

The mean value that improves trend entropy, common trend entropy, risk index putting in order from small to large listed in table 4.

Each index of table 4 puts in order

As can be seen from Table 4, the ordering trend of improving trend entropy and common trend entropy is roughly the same, but change has taken place in the ordering of part of nodes.For example, node 32 and 39 ordering.As can be seen from Table 3, the out-of-limit risk index of the trend of node 39 is more much bigger than node 32, and the out-of-limit degree of trend of this explanation node 32 is smaller, and the out-of-limit degree of node 39 trends is more serious.Therefore, the improvement trend entropy of node 32 is littler than node 39, has also just overcome the deficiency of common trend entropy.Every index of improving the trend entropy during wind energy turbine set access node 32 in the observation table 1 can find, its average, variance, these several of maximums are all smaller.Therefore 32 pairs of systems of wind energy turbine set access node influence minimum, corresponding operation and maintenance cost also can significantly reduce.

Claims (3)

1. method is determined in the also site of an intermittent energy source, is used for selecting optimum also site from a plurality of optional intermittent energy source of electrical network and site; It is characterized in that, the improvement trend entropy of described electrical network when calculating described intermittent energy source and inserting each optional intermittent energy source and site respectively, and select to make electrical network improvement trend entropy minimum and the site as optimum and the site; The improvement trend entropy of described electrical network calculates according to following formula:

$\tilde{H}=-C\underset{i}{\mathrm{\&Sigma;}}{a}_i{p}_i\ln p_i,$

Wherein,

Expression improves the trend entropy; C is constant; p _iThe interval U of expression load factor _iIn the circuit number account for the ratio of grid bus way; a _iBe the interval U of load factor _iTrend entropy penalty coefficient, determine according to following formula:

$a_i=\left\{\begin{array}{cc}1,& 0\&le;{\mathrm{\&mu;}}_{i,\mathrm{mid}}\&le;1\\ {\stackrel{\&OverBar;}{\mathrm{\&mu;}}}_i,& {\mathrm{\&mu;}}_{i,\mathrm{mid}}>1\end{array}\right.,$

Wherein, μ _{I, mid}Be the interval U of load factor _iMidrange;

Be the interval U of load factor _iIn the mean value of each line load rate.

2. method is determined in the also site of intermittent energy source according to claim 1, it is characterized in that the value of described constant C is ln10.

According to claim 1 intermittent energy source and the site determine method, it is characterized in that the improvement trend entropy of described electrical network when calculating described intermittent energy source and inserting each optional intermittent energy source and site respectively adopts the Monte Carlo simulation method.

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