CN104504620A - Safety economic comprehensive optimization based power grid targeting planning design method - Google Patents

Abstract

By means of a traditional power grid planning method, a capacity expansion scheme optimized in a static-state safety margin is not easily obtained, and the economic benefit with optimized capacity expansion cost is far lower than the benefit with optimized operation cost (namely power generation cost and grid loss). The invention provides a safety economic comprehensive optimization based power grid targeting planning design method. Based on a preliminary research foundation (Chinese patent: power generation and transmission and power grid safety comprehensive optimization based modeling method, CN104103023A), a comprehensive optimization model is utilized and the static-state safety margin is opened to perform optimization; lines and reactive compensation nodes (namely targets) required to be expanded are looked for and 'targeting capacity expansion design' is performed according to the optimized trend and safety margin. An IEEE39 node system calculation example verifies the 'target' finding rationality of the method. By means of the method, the capacity expansion scheme meeting the requirement for power system safety economic optimized operation can be obtained.

Description

Based on the electrical network target planning and designing method of safety economy complex optimum

Technical field

Electric system (electrical network) is planned.

Background technology

Traditional Electric power network planning method is generally according to load and power distribution situation and the method for operation of some, is meeting under safety conditions, is determining rack dilatation scheme and the reactive compensation capacity of better economy.

In economy, traditional Electric power network planning method is main it is considered that electric grid investment cost, considers not enough to operation.In fact, the economy that the economy that electric system (generating and transmission of electricity) runs is invested more than electrical network dilatation is important, because operating cost (cost of electricity-generating and the Transmission Loss) difference continued is much larger than the different cost of investment difference caused of electrical network dilatation bill.So the economy of Electric Power Network Planning more should consider the overall economics of Operation of Electric Systems, this is the financial responsibility of grid company self and the social responsibility as stateowned enterprise.

In security, first Electric Power Network Planning needs to meet static security boundary constraint, i.e. the upper limit of circuit effective power flow and the upper and lower limit of node voltage.Therefore traditional planing method is block the way of secure border to static security, be difficult to obtain the rack dilatation scheme optimized in security domain.

For these problems, based on early-stage Study basis (Chinese invention patent: the modeling method sending out transmission of electricity economy and power grid security complex optimum, CN104103023A), utilize the Integrated Optimization Model that the method obtains, decontrol static security border to be optimized, according to the trend after optimization and security border, find and need the circuit of dilatation and idle node (i.e. target), then carry out the design of dilatation targetedly.

The method can be met the electrical network dilatation scheme of electric system economic security optimizing operation.

Summary of the invention

The present invention's " electrical network target planning and designing method based on safety economy complex optimum ", based on early-stage Study basis (Chinese invention patent: the modeling method sending out transmission of electricity economy and power grid security complex optimum, CN104103023A), utilize this Integrated Optimization Model and decontrol static security border and be optimized; Again according to the trend after optimization and security border, find and need the circuit of dilatation and idle node (i.e. target), and carry out " target dilatation design ".The method can be met the electrical network dilatation scheme of electric system economic security optimizing operation.

Accompanying drawing explanation

Fig. 1 electrical network-mapping elastic network(s) Topological Mapping, (1) electrical network, (2) map elastic network(s)

The equivalence of Fig. 2 electrical network maps elasticity branch road

Fig. 3 transmission line of electricity Equivalent Model

Fig. 4 IEEE39 node system structure

Embodiment

1. the mapping elastic potential energy of electrical network

If L two ends, alternating current circuit node voltage phase differential be θ _l, active power is P _l, reactance is X _l, negligible resistance.Work as U _l1, U _l2when changing little, the merit-angle characteristic of circuit L and single-degree-of-freedom elasticity branch road l stressed-deformation behavior is similar, sets up L and l quantity of state mapping relations as follows

$\left\{\begin{array}{c}{P}_L=F_l\\ {\mathrm{\θ}}_L=x_l\\ k_L=k_l\end{array}\right.---\left(1\right)$

In above formula, F _l, x _land k _lbe respectively the acting force of l, elongation and elasticity coefficient; k _lfor the mapping elasticity coefficient of L.Wherein

$\left\{\begin{array}{c}{k}_L=d{P}_L/d{\mathrm{\θ}}_L\\ k_l=d{F}_l/{\mathrm{dx}}_l\end{array}\right.---\left(2\right)$

If the active power of L transmission represents be

$P_L=\frac{U_{L1}{U}_{L2}}{X_L}\sin {\mathrm{\θ}}_L---\left(3\right)$

Then have

$\left\{\begin{array}{c}{k}_L=C\cos {\mathrm{\θ}}_L\\ k_l=C\cos x_l\end{array}\right.---\left(4\right)$

$\left\{\begin{array}{c}{P}_L=k_L\·\tan {\mathrm{\θ}}_L\\ F_l=k_l\·\tan x_l\end{array}\right.---\left(5\right)$

Wherein, according to physical definition, the elastic potential energy of l is

E _l＝∫F _ldx _l(6)

Can obtain

$E_l=F_l\tan \frac{x_l}{2}=k_l\frac{1-\cos x_l}{\cos x_l}=\frac{\cos x_l}{1+\cos x_l}\·\frac{{F_l}^2}{k_l}---\left(7\right)$

According to mapping relations, the mapping elastic potential energy of L is

$E_L=P_L\tan \frac{{\mathrm{\θ}}_L}{2}=k_L\frac{1-\cos {\mathrm{\θ}}_L}{\cos {\mathrm{\θ}}_L}=\frac{\cos {\mathrm{\θ}}_L}{1+\cos {\mathrm{\θ}}_L}\·\frac{{P_L}^2}{k_L}---\left(8\right)$

If θ _lless, L can be mapped as linear elasticity branch road, has

$\left\{\begin{array}{c}{k}_L=k_l\≈1/X_L\\ P_L\≈k_L{\mathrm{\θ}}_L\\ F_l\≈k_l{x}_l\end{array}\right.---\left(9\right)$

$\left\{\begin{array}{c}{E}_l=\frac{1}{2}{F}_l{x}_l=\frac{1}{2}{k}_l{x_l}^2=\frac{{F_l}^2}{{2k}_l}\\ E_L=\frac{1}{2}{P}_L{\mathrm{\θ}}_{\mathrm{ij}}=\frac{1}{2}{k}_L{{\mathrm{\θ}}_{\mathrm{ij}}}^2=\frac{P_L^2}{{2k}_L}\end{array}\right.---\left(10\right)$

If elastic network(s) is made up of n bar branch road, its total potential energy E _{l Σ}meet linear superposition characteristic; The mapping elastic potential E of electrical network _{l Σ}also be like this.Namely

$E_{\mathrm{l\Σ}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{E}_{\mathrm{li}}---\left(11\right)$

$E_{\mathrm{L\Σ}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{E}_{\mathrm{Li}}---\left(12\right)$

Wherein: E _lifor i-th Branch Potential Energy of elastic network(s), E _lifor i-th branch road of electrical network maps elastic potential energy.

The mapping relations of potential energy as shown in the formula

E _{l Σ}=E _{l Σ}(13) 2. electrical network merit-angle security with map the relation of elastic potential energy

According to patent of invention " electrical network-elastic mechanics network topology mapping method " (authorizing publication No.: CN 102227084B), electrical network is mapped to vertically stressed elastic network(s), and keeps the incidence relation of node, branch road constant, as shown in Figure 1.Because branch road is all longitudinal stress, as long as total therefore all equal with total load with potential energy, available 1 elasticity branch road equivalence, in like manner, electrical network also uses a branch road equivalence, as shown in Figure 2.Quantity of state mapping relations are

$\left\{\begin{array}{c}{k}_{\mathrm{leq}}=k_{\mathrm{Leq}}\\ x_{\mathrm{leq}}={\mathrm{\θ}}_{\mathrm{Leq}}\\ F_{\mathrm{\Σ}}=P_{\mathrm{\Σ}}\\ E_{\mathrm{l\Σ}}=E_{\mathrm{L\Σ}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{E}_{\mathrm{li}}=\underset{i=1}{\overset{n}{\mathrm{\Σ}}}{E}_{\mathrm{Li}}\end{array}\right.---\left(14\right)$

Wherein, k _leq, k _leqbe respectively the elasticity coefficient (rigidity) of equivalence and map elasticity coefficient, x _leq, θ _leqbe respectively deformation and the phase differential of equivalence, F _Σ, P _Σbe respectively the total load-bearing of elastic network(s) and the total burden with power of electrical network.

According to announce to apply for a patent " based on mapping the electric network active load-bearing capacity quantitative test index of elastic potential energy " (application publication number: CN 103474993A) known, when total load one timing, from the overall angle of electrical network, E _{l Σ}be approximated to direct ratio with equivalent deformation, be approximated to inverse ratio with equivalent stiffness; From interior angle, when the meritorious distribution of branch road is the most balanced, then E _{l Σ}minimum, namely when meeting

P _L1:P _l2:…:P _Ln＝k _L1:k _L2:…:k _Ln(15)

Then E _{l Σ}approximate minimum.

So, map elastic potential energy both omnidistance overall merit-angle characteristics reflecting electrical network quantitatively, meet again actual conditions that are harmonious and security, can be used as the quantitative target of electric network security.

3. the transmission of electricity economy of power transmission network and the relation of mapping elastic potential energy

Transmission of electricity economy can be measured by network loss, and network loss is less, then economy of transmitting electricity is better.

Analyze the general rule found in an electrical network Practical Project: if the impedance ratio of circuit is close in major network, network loss △ P _Σwith mapping elastic potential energy E _{l Σ}approximate with becoming, and be all tending towards minimum when meritorious distribution is the most balanced.

1) △ P _Σ, E _{l Σ}approximate to be analyzed as follows with taxis:

If circuit i both end voltage is end power is P _li+ jQ _li, impedance is R _i+ jX _i, susceptance is B _i, ignore conductance, Π shape Equivalent Model as shown in Figure 3.If △ is P _ifor the active loss of circuit i, then

${\mathrm{\ΔP}}_i=\frac{{P_i}^2+Q_i^2}{U_{i2}^2}{R}_i=\frac{P_{\mathrm{Li}}^2+{(Q_{\mathrm{Li}}-B{U}_{i2}^2/2)}^2}{U_{i2}^2}{R}_i---\left(16\right)$

In trunk power transmission network, if reactive-load compensation is comparatively strong, node voltage amplitude all remains near reference value, then Q _li< < P _li; If ignore conductance again, then multi-line power transmission loss is approximately

${\mathrm{\&Delta;P}}_i\&ap;P_{\mathrm{Li}}^2{R}_i---\left(17\right)$

Therefore network loss is approximately

$\mathrm{\&Delta;}{P}_{\mathrm{\&Sigma;}}\&ap;\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{P}_{\mathrm{Li}}^2{R}_i---\left(18\right)$

Consider the nonlinear characteristic at circuit merit-angle, adopt Nonlinear Mapping, according to civilian Chinese style (18), (4), (8), network loss is

$\mathrm{\&Delta;}{P}_{\mathrm{\&Sigma;}}\&ap;\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{P}_{\mathrm{Li}}^2\frac{\cos {\mathrm{\&theta;}}_{\mathrm{Li}}}{k_{\mathrm{Li}}}\&CenterDot;\frac{R_i}{X_i}\&ap;\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}(1+\cos {\mathrm{\&theta;}}_{\mathrm{Li}})E_{\mathrm{Li}}\&CenterDot;\frac{R_i}{X_i}---\left(19\right)$

In major network, general circuit two ends phase angle difference is little.In order to satisfied static reserve factor, generator built-in potential static limit merit angle to its supply load is farthest 56.4 °, comprising the phase angle difference of generator inner rotor angle, major network middle line and distribution line.For IEEE39 node system regular run mode, line Phases angle is about 10 ° to the maximum.From formula (19): the Main Factors of network loss change is the mapping elastic potential energy of circuit.

If phasing degree, branch road two ends is less, linear elasticity branch road can be mapped as, all can obtain by above formula or by formula (18), (9) and (10)

$\mathrm{\&Delta;}{P}_{\mathrm{\&Sigma;}}\&ap;\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{P}_{\mathrm{Li}}^2\frac{1}{k_{\mathrm{Li}}}\&CenterDot;\frac{R_i}{X_i}\&ap;\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}2E_{\mathrm{Li}}\&CenterDot;\frac{R_i}{X_i}---\left(20\right)$

In actual major network, the impedance ratio of the high-tension overhead line of employing is substantially close, all at an order of magnitude.If the R of all branch roads in electrical network _i/ X _i≈ a, a are constant, can be obtained by formula (20)

△ P _Σ≈ 2aE _{l Σ}(21) visible, keep good at grid nodes voltage, and line impedance is than when being more or less the same, the mapping elastic potential energy E of electrical network _{l Σ}with network loss △ P _Σapproximate with becoming.

2) prove again below: if load is all constant, and line impedance is than close, △ P _Σand E _{l Σ}when meritorious distribution is the most balanced with being tending towards minimum.Prove as follows:

Build following Lagrange function

$f=\mathrm{\&Delta;}{P}_{\mathrm{\&Sigma;}}-\mathrm{\&lambda;}(\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}{P}_{\mathrm{Li}}-P_{\mathrm{\&Sigma;}})---\left(22\right)$

Wherein, λ is certain constant.△ P _Σthe condition that there is extreme value is that above formula is to P _lipartial derivative be zero, namely

$\frac{\&PartialD;f}{\&PartialD;P_{\mathrm{Li}}}=\frac{\&PartialD;\mathrm{\&Delta;}{P}_{\mathrm{\&Sigma;}}}{\&PartialD;P_{\mathrm{Li}}}-\mathrm{\&lambda;}\frac{\&PartialD;}{\&PartialD;P_{\mathrm{Li}}}(\underset{i}{\overset{n}{\mathrm{\&Sigma;}}}{P}_{\mathrm{Li}}-P_{\mathrm{\&Sigma;}})=0---\left(23\right)$

Therefore have

$\frac{\&PartialD;\mathrm{\&Delta;}{P}_{\mathrm{\&Sigma;}}}{\&PartialD;P_{\mathrm{Li}}}-\mathrm{\&lambda;}(1-0)=0---\left(24\right)$

Formula (19) is substituted into above formula, can obtain

$\frac{{2a}_i{P}_{\mathrm{Li}}}{K_{\mathrm{Li}}}=\mathrm{\&lambda;}---\left(25\right)$

If R _i/ X _i≈ a, arrives formula (15) can be obtained fom the above equation.When namely meeting formula (15), △ P _Σbe approximately extreme value.Unique by the known minimal value of actual conditions, therefore be approximately minimum value.Analyzed from Section 2: when meeting formula (15), then the mapping elastic potential energy E of electrical network _{l Σ}minimum.So, △ P _Σand E _{l Σ}when meritorious distribution is the most balanced with being tending towards minimum.Card is finished.

Can gaining enlightenment from the rule found: when generating electricity, if the impedance ratio of major network circuit is close, exerted oneself by the meritorious of reasonable distribution unit, reducing the mapping elastic potential energy of major network, generally can improve the security of electrical network and the economy of transmission of electricity simultaneously.

4., transmission of electricity economy and safety comprehensive Optimized model

Traditional generating economical optimum model owing to not comprising the electric network security index of quantification in target, therefore cannot be optimized electric network security.Traditional generating economical optimum model is generally

Objective function:

$\min f_G=\underset{i=1}{\overset{n_g}{\mathrm{\&Sigma;}}}(a_i{P}_{\mathrm{Gi}}^2+b_i{P}_{\mathrm{Gi}}+c_i)---\left(26\right)$

Constraint condition:

1) trend equality constraint

$B_{\mathrm{ii}}{\mathrm{\&theta;}}_i+\underset{\underset{j\&NotEqual;s}{\mathrm{jwi}}}{\mathrm{\&Sigma;}}{B}_{\mathrm{ij}}{\mathrm{\&theta;}}_j-P_{\mathrm{Gi}}+P_{\mathrm{Di}}=0,i\&Element;S_B---\left(27\right)$

Or $\left\{\begin{array}{c}{P}_{\mathrm{Gi}}-P_{\mathrm{Di}}=U_i\underset{j\&Element;i}{\mathrm{\&Sigma;}}{U}_j(G_{\mathrm{ij}}\cos {\mathrm{\&theta;}}_{\mathrm{ij}}+B_{\mathrm{ij}}\sin {\mathrm{\&theta;}}_{\mathrm{ij}})\\ Q_{\mathrm{Gi}}-Q_{\mathrm{Di}}=U_i\underset{j\&Element;i}{\mathrm{\&Sigma;}}{U}_i(G_{\mathrm{ij}}\sin {\mathrm{\&theta;}}_{\mathrm{ij}}-B_{\mathrm{ij}}\cos {\mathrm{\&theta;}}_{\mathrm{ij}})\end{array}\right.---\left(28\right)$

2) the meritorious bound constraint of exerting oneself of unit

P _Gimin≤P _Gi≤P _Gimaxi∈S _G(29)

3) circuit effective power flow constraint

P _i≤P _imaxi∈S _L(30)

4) node voltage amplitude bound constraint

U _imin≤U _i≤U _imaxi∈S _B(31)

Wherein: f _gfor total power production cost; a _i, b _i, c _ifor the economic parameters of unit i; B _iiand B _ijbe respectively self-admittance and transadmittance; P _girepresent meritorious the exerting oneself of unit i; P _di, Q _difor the load of node i; P _giminand P _gimaxbe respectively the meritorious upper and lower limit of exerting oneself of unit; P _imaxfor the meritorious upper limit of circuit i; U _i, U _jfor the voltage magnitude of node i, j; U _imin, U _imaxbe respectively node i voltage magnitude upper and lower limit; S _b, S _land S _gthe node comprised for system, circuit and unit set.

Have for making model send out, transmission of electricity economy and the function of electric network security complex optimum, in objective function, superpose the mapping elastic potential energy index of major network, and weighting, to reach the effect of complex optimum.Change into by formula (26)

minf＝α·f _G+β·μ·E _LΣ(32)

Wherein: α, β are the weight factor of the two, can arrange according to the actual conditions of different electrical network, and meet alpha+beta=1; 0≤α≤1; 0≤β≤1.Due to f ₁, f ₂there is different dimensions and the order of magnitude, so f ₂be multiplied by coefficient μ, make the two or variation range have comparability.

It should be noted that, the actual conditions of each electrical network are different, and as payload and distribution, source-net coordination degree, stressing in degree etc. at economics of power generation and electric network security, therefore the value of α, β is also different, is empirical value.

Compare traditional generating economical optimum model, this Integrated Optimization Model also has the optimizational function of transmission of electricity economy and electric network security, and only has 2 target indicator components.

5. based on the electrical network target planning and designing method of economic security complex optimum

Because the mapping elastic potential energy in objective function is less, branch road is meritorious more balanced, branch road is meritorious be more not easy out-of-limit.In addition, according to transmission line of electricity Equivalent Model, the voltage amplitude value difference at branch road two ends is

$U_{i1}-U_{i2}\&ap;\frac{P_i{R}_i+Q_i{X}_i}{U_{i2}}---\left(33\right)$

R in general circuit _i< < X _i.Formula (33) is visible, when circuit active load rate is more balanced and reactive-load compensation is better, and P _ir and Q _ix _iall little, branch road both end voltage difference in magnitude is little, therefore node voltage is not easy out-of-limit.

So when grid structure is better, reactive power compensation planning is comparatively strong and source-net is coordinated better, circuit is gained merit and node voltage is not easy out-of-limit.

Therefore according to this feature, propose the target planning and designing method of electrical network:

1) in Integrated Optimization Model, decontrol security boundary constraint, namely omit formula (30), (31), hold mode (32), (27) or (28), (29);

2) complex optimum decontroling security border is carried out, the trend after being optimized;

3) gain merit the branch road in Optimal Power Flow P _iIop, node voltage U _iIopwith corresponding safe edge dividing value P _imax, U _iminand U _imaxcompare one by one, with out-of-limit or approach the circuit of secure border and node for target, carry out the target planning and design of electrical network;

4) if the circuit active-power P after optimizing _ijIop>P _ijmaxor approach P _ijmax, then show that this circuit needs dilatation, or the electrical network of the secondary voltage level connecting this circuit needs dilatation;

5) if the node voltage U after optimizing _iIop<U _iminor approach U _imin, then show that this node reactive compensation capacity needs dilatation;

6) if if the node voltage U after optimizing _iIop>U _imaxor approach U _imax, then show that this node need set up parallel reactance.

6. sample calculation analysis

As shown in Figure 4, its median generatrix 31 is balance node to IEEE39 node system structure, and generator operation economic parameters is as shown in table 1.

Decontrol secure border constraint condition, namely omit formula (30), (31), form Integrated Optimization Model by formula (32), (28), (29); For making total power production cost f ₁with the mapping elastic potential energy E of electrical network _{l Σ}there is comparability, get μ=25; Successively decrease according to α, the rule that β increases progressively, 5 groups of weights of target setting function; Adopt quadratic programming optimized algorithm, under obtaining 5 kinds of generation modes, the meritorious of each unit is exerted oneself, as table 2.Carry out complex optimum after decontroling security constraint, in the Optimal Power Flow obtained, only have circuit 2-3 power out-of-limit, as shown in table 3.

Table 1 unit operation economic parameters

Table 2 unit is gained merit output distribution

Circuit 2-3 active power after secure border complex optimum decontroled by table 3

Sample calculation analysis is as follows:

1) table 3 is visible, and after complex optimum (scheme 3,4) and safety-optimized (scheme 5), circuit 2-3's is meritorious out-of-limit, shows that this circuit is the dilatation target in 39 node systems.

2) table 3 is visible, and during circuit 2-3 meritorious out-of-limit, circuit merit angle is just just more than 4 °.In 39 node systems, the load of node 3 is actually the electrical network total load of secondary voltage level, the active power of circuit 2-3 and merit arm of angle dividing value little, show that the electrical network of the secondary voltage level of connected node 3 is also dilatation target, urgent need carries out circuit dilatation, strengthens static security.

7. conclusion

Tradition Electric power network planning method is in economy, main it is considered that electric grid investment cost optimization, consider not enough to the method for operation, operating cost (cost of electricity-generating and the Transmission Loss) difference continued is much larger than the different cost of investment difference caused of electrical network dilatation bill.In security, only require and meet boundary constraint, be difficult to obtain the rack dilatation scheme that security is optimized.

For these problems, based on early-stage Study basis (Chinese invention patent: the modeling method sending out transmission of electricity economy and power grid security complex optimum, CN104103023A), utilize this Integrated Optimization Model and decontrol static security border and be optimized, according to the trend after optimization and security border, can find and need the circuit of dilatation and idle node (i.e. target), and carry out the design of dilatation targetedly.

The method can be met the electrical network dilatation scheme of electric system economic security optimizing operation.

Claims (1)

1., based on an electrical network target planning and designing method for safety economy complex optimum, the method is characterised in that, comprises the steps:

1) build transmission of electricity economy and a power grid security Integrated Optimization Model, objective function is minf=α f _g+ β μ E _{l Σ}, trend equality constraint is $B_{\mathrm{ii}}{\mathrm{\&theta;}}_i+\underset{j\&NotEqual;s}{\underset{\mathrm{jwi}}{\mathrm{\&Sigma;}}}{B}_{\mathrm{ij}}{\mathrm{\&theta;}}_j-P_{\mathrm{Gi}}+P_{\mathrm{Di}}=0$ Or $\left\{\begin{array}{c}{P}_{\mathrm{Gi}}-P_{\mathrm{Gi}}=U_i\underset{j\&Element;i}{\mathrm{\&Sigma;}}{U}_j(G_{\mathrm{ij}}\cos {\mathrm{\&theta;}}_{\mathrm{ij}}+B_{\mathrm{ij}}\sin {\mathrm{\&theta;}}_{\mathrm{ij}})\\ Q_{\mathrm{Gi}}-Q_{\mathrm{Di}}=U_i\underset{j\&Element;i}{\mathrm{\&Sigma;}}{U}_j(G_{\mathrm{ij}}\sin {\mathrm{\&theta;}}_{\mathrm{ij}}-B_{\mathrm{ij}}\cos {\mathrm{\&theta;}}_{\mathrm{ij}})\end{array}\right.,$ The meritorious bound of exerting oneself of unit is constrained to P _gimin≤ P _gi≤ P _gimax, circuit effective power flow is constrained to P _ij≤ P _ijmax, node voltage amplitude bound is constrained to U _imin≤ U _i≤ U _imax;

2) step 1) in, f _gfor connecting the total power production cost of all units of major network, E _{l Σ}for the mapping elastic potential energy of major network, α, β are weight factor, and the actual conditions according to different electrical network are arranged, and meet alpha+beta=1,0≤α≤1,0≤β≤1, coefficient μ makes f _g, μ E _{l Σ}there is the identical order of magnitude;

3) step 1) in, B _iiand B _ijbe respectively self-admittance and transadmittance; P _di, Q _difor the load of node i; P _giminand P _gimaxbe respectively the meritorious upper and lower limit of exerting oneself of unit i; P _imaxfor the meritorious upper limit of circuit i; U _i, U _jfor the voltage magnitude of node i, j; U _imin, U _imaxbe respectively the voltage magnitude upper and lower limit of node i;

4) step 1) in, p _gi, a _i, b _i, c _ibe respectively the meritorious of unit i to exert oneself and economic parameters, E _libe the mapping elastic potential energy of i-th circuit, n _g, n is respectively the quantity of generator and circuit;

5) utilize step 1) in objective function, trend equality constraint and unit output bound constraint carry out complex optimum, be optimized trend;

6) gain merit the branch road in Optimal Power Flow P _iIop, node voltage U _iIopwith corresponding safe edge dividing value P _imax, U _iminand U _imaxcompare one by one, with out-of-limit or approach the circuit of secure border and node for target, carry out the target planning and design of electrical network;

7) if the circuit active-power P after optimizing _ijIopbe greater than or approach P _ijmax, then show that this circuit needs dilatation, or the electrical network of the secondary voltage level connecting this circuit needs dilatation;

8) if the node voltage U after optimizing _iIopbe less than or approach U _imin, then show that this node reactive compensation capacity needs dilatation;

9) if if the node voltage U after optimizing _iIopbe greater than or approach U _imax, then show that this node need set up parallel reactance.