CN101876988A - Chaos searching method of economic load dispatching of electric power system - Google Patents

Abstract

The invention belongs to the field of optimization dispatching, in particular to a chaos searching method of economic load dispatching of an electric power system. Acquired data are processed by using a computer, and the chaos searching method of economic load dispatching of the electric power system with complex constraint condition is formed. In the method, the original interval of variable searching is determined according to physical conditions of the actual electric power system, the important searching space is determined according to the optimal value searched during the optimization, the important searching space and the original searching space are searched simultaneously by different probabilities, and the range of the important searching space is continually reduced. Under the condition of ensuring the global optimizing capability, the optimizing speed can be increased, and the optimizing efficiency is improved. The invention is mainly applied to solving the problems of economic load dispatching and the like of the electric power system.

Description

The chaos searching method of Power System Economic Load Dispatch

Technical field

The invention belongs to Optimization Dispatching and computation optimization field, relate to a kind of chaos optimization method, design a kind of chaos searching method of Power System Economic Load Dispatch especially.

Background technology

Power System Economic Load Dispatch is to make up unit satisfying on the Operation of Electric Systems constraint condition basis, makes cost of electricity-generating minimum.Because of it can obtain the common concern that huge economic benefit and social benefit are subjected to industry under the condition that does not increase any engineering cost.

The classic optimisation algorithm of finding the solution this problem has simple gradient method, linear programming technique, Nonlinear Programming Method, dynamic programming, lagrange's method of multipliers etc.In recent years, methods such as evolutional programming, genetic algorithm, particle cluster algorithm, ant group algorithm, artificial neural network also are applied in the finding the solution of this problem.But because being easy to of existing of this complex nature of the problem and these methods itself is absorbed in defectives such as local extremum, cause the outcome quality of asking not high.Therefore design a kind of high-efficiency search method that addresses this problem and have important use value.

Summary of the invention

Technical matters to be solved by this invention is, designs a kind of chaos searching method of Power System Economic Load Dispatch, especially makes positive contribution effectively handling in the Power System Economic Load Dispatch problem with complicated constraint condition.

The technical solution adopted in the present invention is: a kind of chaos searching method of Power System Economic Load Dispatch, the data of being gathered constitute the chaos searching method of the Power System Economic Load Dispatch with complicated constraint condition by Computer Processing.This method is determined the original search volume of search variables according to the physical conditions of practical power systems, and in this space, repeatedly tentatively search for, be that the focussing search space is determined at the center with current optimum solution again, simultaneously focussing search space and original search volume searched for different probability then.The focussing search spatial dimension is dwindled gradually, and searching probability increases gradually, finally tries to achieve the optimum solution or the satisfactory solution of Power System Economic Load Dispatch.

The objective of the invention is to propose a kind of chaos searching method of Power System Economic Load Dispatch, this method overcomes the existing not high defective of method optimizing efficient, can effectively find the solution the optimization problem of the economy of power plant operation of many units.

Description of drawings

Fig. 1 is the chaos searching method process flow diagram.

Embodiment

Below in conjunction with embodiment and accompanying drawing the present invention is described in further detail.

The optimization purpose of Power System Economic Load Dispatch problem is to satisfy under system's operation constraint condition, the generator output of optimal combination unit, thus making that the total power production cost of system is minimum, its target function is

$F=\min \underset{i=1}{\overset{N_g}{\mathrm{\Σ}}}{F}_i\left(p_i\right)---\left(1\right)$

F is system's expense of always generating electricity in the formula; N _gBe generator sum in the system; p _iIt is i platform generator active power; F _i(p _i) be i platform generator consumption characteristic.For F _i(p _i) with the quadratic function approximate representation be

$F_i\left(p_i\right)=a_i{p}_i^2+b_i{p}_i+c_i---\left(2\right)$

A in the formula _i, b _i, c _iBe parameter.

Power balance constraint condition is

$\underset{i=1}{\overset{N_g}{\mathrm{\Σ}}}{p}_i=p_L+p_D---\left(3\right)$

Generator operation constraint condition is

p _imin＜p _i＜p _imax，i＝1，2.....N _g (4)

P in the formula _DBe system's total load demand; P _LBe the total network loss of system; P _Imin, P _ImaxBe the minimum and the output of maximum active power of i platform generator.The total network loss of system adopts the B Y-factor method Y to calculate, and its relational expression is

p _L＝p ^TB _ggp+p ^TB _g0+B ₀₀ (5)

In the formula, p _L=(p ₁, p ₂..., p _Ng) ^TBe N _gDimension generator active power vector; B _Gg, B _G0, B ₀₀Be the network loss coefficient, i.e. the B coefficient.Wherein, B _GgBe N _g* N _gThe dimension symmetry square matrix; B _G0Be N _gThe dimension column vector; B ₀₀Be constant.

The hot candied phenomenon that when the steam turbine inlet valve is opened suddenly, the occurs pulsation effect that can on the consumption curve of unit, superpose, generation valve point effect.The valve point effect can be expressed as

E _Vi＝|g _isin(h _i(p _i-p _imin))| (6)

E in the formula _ViThe i platform generator consumption characteristic variations that causes for the valve point effect; g _i, h _iBe effect coefficient.

According to different supposed situations, the optimizing function can have three kinds to express situation:

Situation 1: ignore network loss, when ignoring the valve point effect;

$F=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{F}_i\left(p_i\right)+k{|\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{p}_i-p_D|}^2,i=\mathrm{1,2},...,n---\left(7\right)$

Situation 2: ignore network loss, when taking into account the valve point effect;

$F=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{F}_i\left(p_i\right)+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{E}_i+k{|\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_i-P_D|}^2,i=\mathrm{1,2},...n---\left(8\right)$

Situation 3: take into account network loss, when taking into account the valve point effect;

$F=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{F}_i\left(p_i\right)+\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{E}_i+k{|\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{P}_i-P_D-P_S|}^2,i=\mathrm{1,2},...n---\left(9\right)$

K is the penalty function coefficient of constraint condition in the following formula.

At above-mentioned optimization problem, the chaos mechanism that chaos searching method of the present invention adopted is:

y ^k+1＝sin[2/y ^k]，y ^k∈[-1，1]，y ^k≠0 (10)

Produce chaos sequence by this mapping and need satisfy following condition:

(1) initial value of iteration can not be 0;

(2) initial value can not be taken as any one of infinite a plurality of fixed points.

The unification of the described optimizing function of formula (7-9) is designated as:

min?f(x ₁，x ₂，.....x _n)＝minf(x _i)，x _i∈[a _i，b _i]，i＝1，2....n (11)

Chaos searching method step of the present invention is as follows:

A, initialization k=0, r=0,

I=1,2...n.Here k is a Chaos Variable iteration sign, the r search sign of attaching most importance to, x _i ^*Be current optimum solution, current optimal value f ^*Be initialized as a bigger number.

B,

Be mapped to the current search space respectively with Probability p and 1-p

$x_i^k=\left\{\begin{array}{c}{a}_i+y_i^k(b_i-a_i),\mathrm{if}(\mathrm{random}\left(\mathrm{0,1}\right)<p)\\ a_i^r+y_i^k(b_i^r-a_i^r),\mathrm{else}\end{array}\right.---\left(12\right)$

The value of p provides according to focussing search space and former spatial volume magnitude proportion.

$p=\left(\frac{\underset{i=1}{\overset{n}{\mathrm{\&Pi;}}}(b_i^r-a_i^r)}{\underset{i=1}{\overset{n}{\mathrm{\&Pi;}}}(b_i-a_i)}\right)---\left(13\right)$

C, utilize formula (11) to calculate

If

Then

Change steps d then; Otherwise directly change steps d.

d、 k＝k+1。

E, repeating step b, c, d change step f when predetermined number of times.

F, the size of dwindling the focussing search space.

$a_i^{r+1}=x_i^{*}-{\mathrm{\&epsiv;}}^r(b_i^r-a_i^r)---\left(14\right)$

$b_i^{r+1}=x_i^{*}+{\mathrm{\&epsiv;}}^r(b_i^r-a_i^r)---\left(15\right)$

ε wherein ^r=(r/r+1) ²，

g、 $a_i^{r+1}=\max (a_i^r,a_i^{r+1}),$ $b_i^{r+1}=\min (b_i^r,b_i^{r+1}),$ r＝r+1。

H, return step b, till finding optimal value.

Chaotic motion has good ergodicity, but the time that travels through when the search volume is big is longer, causes the optimizing performance to descend.The Chaos Search algorithm that the present invention adopts is searched for luv space and focussing search space simultaneously with different probability, starting stage is big to the luv space searching probability, with dwindling of emphasis point space, gradually with big probabilistic search focussing search space, thereby on the basis that has guaranteed algorithm global optimizing performance, can improve speed of convergence, improve the optimizing performance.

Claims (4)

1. the chaos searching method of a Power System Economic Load Dispatch is characterized in that, the data of being gathered constitute the chaos searching method of the Power System Economic Load Dispatch with complicated constraint condition by Computer Processing.

2. the chaos searching method of Power System Economic Load Dispatch according to claim 1 is characterized in that, this method is determined between the region of initiation of variable search according to the physical conditions of practical power systems.

3. the chaos searching method of Power System Economic Load Dispatch according to claim 1, it is characterized in that, this method is carried out earlier repeatedly initial ranging in global scope, be that the focussing search space is determined at the center with current optimum solution again, simultaneously luv space and emphasis space are searched for different probability then, and the focussing search spatial dimension is dwindled gradually, and searching probability increases gradually.

4. the chaos searching method of Power System Economic Load Dispatch according to claim 1 is characterized in that, plain probability is searched according to determining with the relation of its spatial volume inverse ratio in luv space and emphasis space.

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