CN105761161A - AC and DC power distribution network power supply mode evaluation method - Google Patents

Abstract

The invention relates to an AC and DC power distribution network power supply mode and an evaluation method. According to features of the AC and DC power distribution network, a typical AC and DC power distribution network topology structure is built, evaluation indexes are built respectively from five aspects of technical benefits, economic benefits, social benefits, environmental benefits and the practicality, an entropy weight fuzzy comprehensive evaluation method is then adopted, and a relative superiority and inferiority rank for the typical AC and DC power distribution network power supply mode is obtained according to the evaluation indexes. The method comprises the following steps: (1) a network topology in the typical power distribution network power supply mode is built; (2) an AC and DC hybrid power distribution network evaluation index system is built; and (3) a fuzzy entropy weight evaluation method is adopted to evaluate the typical power supply mode. Compared with the prior art, the method of the invention has the following advantages that an AC and DC power distribution network design and evaluation method for the system is provided, and effective guidance is provided for transformation of the existing distribution network and planning and design of a future AC and DC power distribution network.

Description

A kind of alternating current-direct current power distribution network powering mode evaluation methodology

Technical field

The present invention relates to a kind of alternating current-direct current power distribution network powering mode and evaluation methodology.Feature according to alternating current-direct current power distribution network, set up typical case's alternating current-direct current power distribution network topological structure, evaluation index is set up respectively from technical benefit, economy benefit, social benefit, environmental benefit and five aspects of practicality, adopt again based on entropy weight fuzzy synthetic appraisement method, draw the relative superior or inferior sequence of typical case's alternating current-direct current power distribution network powering mode according to evaluation index.

Background technology

Development along with Power Electronic Technique, compared to pure AC distribution net, direct current supply has certain advantage in many aspects, and such as, it has quality of power supply height, transmission capacity is big, reliability is high, system structure is simple, economy and the advantage such as electric energy loss is low.Correspondingly, the powering mode of distribution network, except traditional Alternating Current Power Supply, occurs in that again day is concerned and the DC distribution net paid attention to and the common Three models such as alternating current-direct current mixing power distribution network in succession.How according to the character of load and construction features, therefrom select the power distribution network electric power-feeding structure pattern that mixed economy technical benefits is best, for the construction of power distribution network and run significant.

DC power-supply system and alternating current-direct current mixed power supply system are relative to the ac power supply system of comparative maturity, all still at an early stage in worldwide, but are subject to the attention of engineering circles and researcher gradually.The current relative merits of existing scholar's economically relative analysis AC distribution net, DC distribution net and alternating current-direct current mixing power distribution network, the feasibility of the ring-type of DC distribution net and two ends topological structure from the Reliability Discussion of key equipment.Research is not yet had to carry out comprehensively comprehensively analyzing and evaluating from alternating current-direct current power distribution network different angles to the AC distribution net containing distributed power source and energy storage device, DC distribution net and alternating current-direct current mixing power distribution network.

Summary of the invention

The present invention is directed to the deficiencies in the prior art, set up the evaluation index powering mode to typical distribution net respectively from technical, economy, social, the feature of environmental protection and five aspects of practicality and be evaluated, it is determined that best power distribution network powering mode.

Technical scheme is as follows:

A kind of alternating current-direct current power distribution network powering mode evaluation methodology, it is characterised in that described method comprises the steps:

(1) network topology under power distribution network typical case's powering mode is set up；

(2) alternating current-direct current mixing power distribution network evaluation index system is set up；

(3) adopt Based on Entropy evaluation methodology that typical case's powering mode is evaluated.

Further, in described step (1), set up the network topology type under power distribution network typical case's powering mode and include alternating current-direct current power distribution network radial network topological structure, DC distribution net radial network topological structure, alternating current-direct current mixing power distribution network radial network topological structure, alternating current-direct current mixing power distribution network both end power supplying network topology structure and alternating current-direct current mixing power distribution network ring network topology structure.

Further, to set up alternating current-direct current mixing power distribution network evaluation index system specific as follows for described step (2):

Step one: establishing techniques evaluation index system, specifically includes herein below:

(1) network harmonic electric current content ratio α:

For AC network, network harmonic electric current content ratio is defined as the meansigma methods of the different total harmonic current content ratio of node, it may be assumed that

${\mathrm{\α}}_{AC}=\frac{\underset{i=1}{\overset{N_{AC}}{\Σ}}{I}_{h,i}^{AC}/I_{0,i}^{AC}}{N_{AC}}---\left(1\right)$

In formula,For the fundamental current virtual value of AC network i-th node,For total harmonic current virtual value of AC network i-th node, N_ACFor the number of AC network node,For AC network i-th node kth (k >=0) subharmonic current virtual value；

For DC network, network harmonic electric current content ratio defines:

${\mathrm{\α}}_{DC}=\frac{\underset{i=1}{\overset{N_{DC}}{\Σ}}{I}_{h,i}^{DC}/I_{0,i}^{DC}}{N_{DC}}---\left(2\right)$

In formula,For the fundamental current virtual value of DC network i-th node,For total harmonic current virtual value of DC network i-th node, N_DCFor the number of DC network node,For DC network i-th node kth (k >=0) subharmonic current virtual value；

(2) network average voltage aberration rate ξ_avg: electric power distribution network average voltage aberration rate represents with the meansigma methods of different voltage node voltage distortion rate, it may be assumed that

${\mathrm{\ξ}}_{avg}=\frac{\underset{i=1}{\overset{N_V}{\Σ}}{\mathrm{\ξ}}_i}{N_V}---\left(3\right)$

In formula, N_VFor the nodes of the DC network of AC network, ξ_iFor the voltage distortion rate of node i, can represent with the percent of the root-mean-square value of this node each harmonic voltage with the ratio of fundamental voltage virtual value, it may be assumed that

${\mathrm{\ξ}}_i=\sqrt{\frac{U_{i,2}^2+U_{i,3}^2+U_{i,4}^2+\mathrm{...}+U_{i,n}^2}{U_{i,1}^2}}\×100\%---\left(4\right)$

In formula, U_i,2,U_i,3,…,U_i,nRepresent each harmonic voltage of node i；For AC network, U_i,1Represent the fundametal compoment of node i, and for DC network, U_i,1Represent the DC component of node i；

(3) amplitude, ao U on average drops in network voltage temporarily:

It is network voltage on average temporary range of decrease degree by the mean value definition of temporary for each node voltage range of decrease degree；

For AC network, the voltage dip amplitude of arbitrary node represents with rated voltage root-mean-square value with the root-mean-square value dropping voltage temporarily, it may be assumed that

${\mathrm{\ΔU}}_{AC}=\frac{\underset{i=1}{\overset{N_{AC}}{\Σ}}{U}_{i-rms1}/U_{i-rms2}}{N_{AC}}---\left(5\right)$

In formula, U_i-rms1The virtual value of voltage, U drop temporarily for node i_i-rms2For node i rated voltage virtual value；

For DC network, arbitrary node is defined as the ratio dropping busbar voltage temporarily with specified busbar voltage, it may be assumed that

${\mathrm{\ΔU}}_{DC}=\frac{\underset{i=1}{\overset{N_{DC}}{\Σ}}{U}_{i-dc}/U_{i-dc}}{N_{DC}}---\left(6\right)$

In formula, U_i-dcFor node i, busbar voltage, U drop temporarily_i-dcSpecified busbar voltage for node i；

(4) the average departure degree d of network voltage:

For AC network, the average departure degree of network voltage is defined as the meansigma methods of each node voltage irrelevance；

For AC network:

$d_{AC}=\frac{\underset{i=1}{\overset{N_{AC}}{\Σ}}{d}_{AC,i}}{N_{AC}}---\left(7\right)$

In formula, d_AC,iVoltage deviation degree for AC network node:

$d_{AC,i}=\frac{(U_{rated-ac,i}-U_{load-ac,i})}{U_{rated-ac,i}}\×100\%---\left(8\right)$

In formula, U_rated-acFor the rated voltage of AC network node i, U_load-acVirtual voltage during load is accessed for AC network node i；

For DC network:

$d_{DC}=\frac{\underset{i=1}{\overset{N_{DC}}{\Σ}}{d}_{DC,i}}{N_{DC}}---\left(9\right)$

In formula, d_DC,iVoltage deviation degree for DC network node i:

$d_{DC,i}=\frac{(U_{rated-dc,i}-U_{load-dc,i})}{U_{rated-dc,i}}\×100\%---\left(10\right)$

In formula, U_rated-dc,iFor DC network node i rated voltage, U_load-dcVirtual voltage during load is accessed for DC network node i；

(5) network line loss Δ P:

Network line loss is defined as each line loss sum:

$\mathrm{\Δ}P=\underset{l=1}{\overset{N_L}{\Σ}}(P_{from,l}-P_{to,l})---\left(11\right)$

In formula, P_from,P_toRespectively l article of direct current of power distribution network or alternating current circuit head end and end active power；N_LFor power distribution network direct current and alternating current circuit sum；

(6) network average line pressure drop Δ U^L:

The meansigma methods that network average line pressure drop is defined as in network all line drops；

For AC distribution net:

${\mathrm{\ΔU}}_{AC}^L=\frac{\underset{l=1}{\overset{N_{ACL}}{\Σ}}{\mathrm{\ΔU}}_{AC,l}}{N_{ACL}}---\left(12\right)$

${\mathrm{\ΔU}}_{AC,l}\≈\frac{P_{AC}{R}_{AC}+Q_{AC}{X}_{AC}}{U_{AC}}---\left(13\right)$

In formula, P_AC、Q_ACRespectively line end active power and reactive power；R_AC、X_ACRespectively line equivalent resistance and equivalent reactance；U_ACFor line end node voltage virtual value；N_ACLFor alternating current circuit sum；

For DC distribution net, network average line pressure drop is defined as:

${\mathrm{\ΔU}}_{DC}^L=\frac{\underset{l=1}{\overset{N_{DCL}}{\Σ}}{\mathrm{\ΔU}}_{DC,l}}{N_{DCL}}---\left(14\right)$

${\mathrm{\ΔU}}_{DC,l}\≈\frac{P_{DC}{R}_{DC}}{U_{DC}}---\left(15\right)$

In formula, P_DCFor DC line end active power；R_DCEquivalent resistance for direct current cables；U_DCFor DC line endpoint node voltage；N_DCLFor DC line sum；

(7) the temporary frequency reducing of network voltage time N_F: the voltage dip frequency refers to the number of times that in certain time, voltage dip occurs, and its numerical value is more high then more high on the frequent degree of the impact of sensitive load, and the voltage dip frequency method of estimation based on user satisfaction is as follows:

$N_F=\underset{l=1}{\overset{N_L}{\Σ}}{\mathrm{\δ}}_l{L}_l---\left(16\right)$

In formula, δ_l、L_lRespectively the fault rate of l article of circuit and this circuit are in the length in dissatisfied region；

(8) the stability K of network bus voltage_V: the average stability of all nodes in this index expression network, adopt maximum loadability as the voltage stability margin of system, adopt power margin index K_VReflect the power [11] of node:

$K_V=\frac{\underset{i=1}{\overset{N_V}{\Σ}}{K}_{V,i}}{N_V}---\left(17\right)$

$K_{V,i}=\frac{P_{cr,i}-P_{o,i}}{P_{o,i}}---\left(18\right)$

In formula, P_cr,iPower limit for node i；P_o,iOperation power for node i；Due to the problem that DC network is absent from busbar voltage stability, it is believed that K_V=1；

(9) " N-1 " can turn for rate:

" N-1 " can turn the rate of confession and refer to that power distribution network is when losing 1 element, turns the ratio accounting for total load for load:

${\mathrm{\α}}_{N-1}=\frac{\underset{i=1}{\overset{N_V}{\Σ}}{P}_{rec1,i}}{\underset{i=1}{\overset{N_V}{\Σ}}{P}_{load,i}}\×100\%---\left(19\right)$

In formula, P_rec1,iFor there is the load power of " N-1 " fault posterior nodal point i；P_load,iLoad power for the front nodal point i that breaks down；

(10) " N-2 " can turn for rate:

" N-2 " can turn the rate of confession and refer to that power distribution network is when losing 2 elements, turns the ratio accounting for total load for load:

${\mathrm{\α}}_{N-2}=\frac{\underset{i=1}{\overset{N_V}{\Σ}}{P}_{rec2,i}}{\underset{i=1}{\overset{N_V}{\Σ}}{P}_{load,i}}\×100\%---\left(20\right)$

In formula, P_rec2,iFor there is the load power of " N-2 " fault posterior nodal point i；

(11) line efficiency γ_E:

Refer to when electrical network is in peak load running status, the ratio of apparatus of load and equipment rated capacity, it is mainly used in quantifying the loading condition of equipment in electrical network:

${\mathrm{\γ}}_E=\underset{1\≤l\≤N_L}{min}{\mathrm{\γ}}_{L,l}---\left(21\right)$

${\mathrm{\γ}}_{L,l}=\frac{P_{from,l}}{P_{L,l}^{\max }}---\left(22\right)$

In formula, γ_L,lIt is the load factor of l article of circuit, the i.e. utilization rate of l article of circuit；Maximum transfer capacity for circuit；

(12) power autonomous user's ratio such as distributed power generation, energy storage: this index expression distributed power source and energy storage device generated energy be the ratio in institute's power consumption in customer charge, defines as follows:

$D_d=\frac{W_{dis-sto}}{W_{load}}\×100\%---\left(23\right)$

In formula, W_dis-stoThe electricity (kW h) of customer charge is supplied for distributed power source and energy storage device；W_loadFor customer charge power consumption (kW h)；

Step 2: set up Reliability Evaluation system, specifically include herein below:

(8) mean failure rate frequency of power cut in SAIFI: one year total frequency of power cut divided by total number of users (secondary/user's year)；

$SAIFI=\frac{\underset{j=1}{\overset{N_C}{\Σ}}{N}_j^{US}}{N_C}---\left(24\right)$

In formula, N_CFor total number of users；For the frequency of power cut in user j 1 year；

(9) user's System average interruption duration average power off time of each user in SAIDI: a year；

$SAIDI=\frac{\underset{j=1}{\overset{N_C}{\Σ}}{T}_j}{N_C}---\left(25\right)$

In formula, T_jTotal time is continued for having a power failure in user j 1 year；

(10) the power supply reliability power supply hourage that in ASAI: a year, the hourage that do not have a power failure of user requires altogether divided by user；

$ASAI=\frac{T_h\×N_C-\underset{j=1}{\overset{N_C}{\Σ}}{T}_j}{T_h\×N_C}---\left(26\right)$

In formula, T_hRepresent stipulated time domestic demand electricity hourage, for instance within 1 year, be unit, general T_h=8760；

(11) system total electricity deficiency index ENS: system in 1 year because having a power failure and causing the total electric quantity loss of user；

$ENS=\underset{i=1}{\overset{N_C}{\Σ}}{E}_{loss,i}---\left(27\right)$

In formula, E_loss,iFor user's electric quantity loss that i & lt power failure causes；

(12) average power off time CAIDI: the System average interruption duration of fault outage every time；

$CAIDI=\frac{\underset{j=1}{\overset{N_C}{\Σ}}{T}_j}{\underset{j=1}{\overset{N_C}{\Σ}}{N}_j^{US}}---\left(28\right)$

Above-mentioned power supply reliability index all according to the fault rate of power distribution network distinct device, can adopt Monte Carlo simulation method to be calculated；

(13) the continued power time CT of specific investment cost

The reflection of this index increases or keeps in repair the investment of the circuit/distributed power source/energy storage device contribution to reliability newly, newly-increased or maintenance of equipment all can reduce the fault rate of relevant device, therefore this refers to that target value is more big, then it represents that the contribution degree improving distribution network reliability is more big；This index has an appreciable impact for the radial electrical distribution net providing high power supply reliability relatively low, and less for power distribution network contribution degree that reliability is higher；

$C_T=\underset{1\≤i\≤N_{EC}}{min}\frac{T_h\×A_{SAI,i}}{C_{R,i}}---\left(29\right)$

In formula, N_ECFor the device type sum in network；A_SAI,iThe power supply reliability of power distribution network after representing newly-increased or safeguarding the i-th kind equipment；C_R,iRepresent newly-increased or maintenance the i-th kind equipment cost:

C_R,i=N_AM,i·(a_EC,i+w_EC,i)(30)

In formula, N_AM,iFor newly-increased or maintenance device type sum；a_EC,iIt it is the unit price of the i-th kind equipment；w_EC,iIt is the unit maintenance cost of the i-th kind equipment, when renewal of the equipment, makes w_EC,i=0, when maintenance of equipment, make a_EC,i=0；

(14) the power supply capacity index GP of specific investment cost

This index expression increases the investment of the transformator/circuit/distributed power source/energy storage device contribution degree to power distribution network power supply capacity newly, and the value of this index is more big, it was shown that specific investment cost is more notable to the raising of power distribution network power supply capacity；

$G_P=\underset{1\≤i\≤N_{EC}}{min}\frac{C_{P,i}}{C_{I,i}}---\left(31\right)$

In formula, C_P,iRepresent the minima of every kind equipment rated capacity sum after increasing i kind equipment:

$C_{P,i}=\underset{1\≤i\≤N_{EC}}{min}\underset{k=1}{\overset{N_{EC,i}}{\Σ}}{P}_{i,k}^{\max }---\left(32\right)$

In formula, N_EC,iIt it is the sum of the i-th kind equipment；It it is the rated capacity of kth equipment in the i-th kind equipment；

C_I,iRepresent the cost of investment of newly-increased i-th kind equipment:

C_I,i=N_add,ia_EC,i(33)

In formula, N_add,iRepresent the quantity being increased by the i-th kind equipment；

The step 3 of the present invention: set up economic evaluation index system, specifically include herein below

(5) equipment investment cost index S_AC/DC

The equipment investment of distribution network planning construction specifically includes that direct current cables and ac cable investment, user's side inverter and commutator investment, exchange, commutator transformer investment^,, exchange, dc circuit breaker investment, middle pressure current conversion station (VSC) investment etc.；

For AC network, not including middle pressure current conversion station in equipment investment, user side does not include contravariant equipment, and the computational methods of equipment investment are as follows:

$S_{AC/DC}=\underset{i=1}{\overset{N_{Eac}}{\Σ}}{N}_{ac,i}{a}_{ac,i}.---\left(34\right)$

In formula, N_Eac,iIt is the number of units of i-th kind of alternating current equipment, a_Eac,iFor the unit price of in AC network i-th kind of equipment, N_EacRequired alternating current equipment type sum is built for AC network；

For DC network, network does not have AC transformer, user side do not have the rectifying installation, equipment investment computational methods to be:

$S_{AC/DC}=\underset{i=1}{\overset{N_{Edc}}{\Σ}}{N}_{dc,i}{a}_{dc,i}---\left(35\right)$

In formula, N_Edc,iIt is the number of units of i-th kind of DC equipment, a_Edc,iFor the unit price of in DC network i-th kind of equipment, N_EdcRequired alternating current equipment type sum is built for DC network；

For alternating current-direct current mixing power distribution network, computational methods ibid, simply include all of key equipment；

(6) equipment depreciation expense D_C:

$D_C=\underset{i=1}{\overset{N_{EC}}{\Σ}}{D}_{C_i}---\left(36\right)$

In formula,It is the yearly depreciation charge of the i-th kind equipment:

$D_{C_i}=S_{B,i}\·r_{C,i}---\left(37\right)$

In formula, S_B,iIt is the i-th kind equipment initial investment, r_C,iIt is the yearly depreciation of the i-th kind equipment, r_C,i=(1-λ_i)/N_Y, λ_iIt is the net salvage of the i-th kind equipment, N_YIt it is the depreciable life of the i-th kind equipment；

(7) effective power supply rate E of specific investment cost_R

This index reflects the investment of the newly-increased transformator/circuit/distributed power source/energy storage device/reactive power compensator percentage contribution to reducing distribution network line loss, E_RValue is more big, it was shown that invest the effect to reducing line loss more obvious；

$E_R=\underset{1\≤i\≤N_{EC}}{min}\frac{{\mathrm{\ΔA}}_i\%}{C_{I,i}}---\left(38\right)$

${\mathrm{\ΔA}}_i\%=\frac{{\mathrm{\ΔW}}_i}{W_S}\×100\%---\left(39\right)$

In formula, Δ A_i% is the line loss per unit after newly-increased i-th kind equipment；ΔW_iThe variable quantity (kW h) of line loss during more non-newly added equipment after expression newly added equipment；W_STotal delivery (kW h) of all power supplys (containing energy storage device) before representing non-newly added equipment；For DC network, reactive-load compensation equipment number of units is 0；

(8) specific investment cost greatest expected electricity sales amount E_P

This index is reflected under specific investment cost, and power distribution network can be supplied to the maximum electricity of user in 1 year, this refers to that target value is more big, and specific investment cost is to E_PContribution degree more high；

$E_P=\frac{E_{max}}{C_E}---\left(40\right)$

In formula, C_EFor electrical network gross investment, $C_E=S_{AC/DC}+D_C++\underset{k=1}{\overset{N_{add,i}}{\Σ}}(C_{R,i}+C_{I,i}+C_{L,i}),$ Reflect the investment corresponding to influence factor such as power supply capacity, power supply reliability, line loss, i.e. cost；E_maxFor electrical network greatest expected electricity sales amount:

$E_{max}=T_h\×N_C\×A_{SAI}\×\underset{j=1}{\overset{N_C}{\Σ}}{P}_{load,j}---\left(41\right)$

In formula, P_load,jAverage active power for user j；

The step 4 of the present invention: set up social evaluation index system, specifically include herein below

With user, the comprehensive score of satisfaction of electrical network is reflected the social benefit of power distribution network, the present invention ask for the process of index adopts herein expert to point mode, every kind of powering mode is carried out to dividing with the angle of user satisfaction；From power supply quality, Standard Service, consultancy service, the electricity charge are paid, 5 aspects of Service Management are evaluated, the full marks of every aspect are 100 points, minimum are divided into 0 point, and analog subscriber is averaged after 5 aspects are given a mark, pass through membership function, meansigma methods is carried out as user satisfaction after obfuscation, further according to the weight of each user, obtains the comprehensive score of user satisfaction:

$G_C=\underset{j=1}{\overset{N_C}{\Σ}}{\mathrm{\ω}}_{C,j}{f}_{C,j}---\left(42\right)$

In formula, ω_C,jFor user's j satisfaction weight, f_C,jFor fuzzy membership angle value；

The step 5 of the present invention: set up feature of environmental protection evaluation index system, specifically include herein below

(3) carbon emission reduction amount: thermal power generation sends the discharge capacity of carbon dioxide that corresponding green energy resource generated energy discharges, is generally adopted following formula and calculates:

$E_{c{o}_2}=0.4\mathrm{kg}/\mathrm{kwh}*2.493*W_g---\left(43\right)$

In formula, W_gFor green energy resource generated energy, unit (kW h)；

(4) clean energy resource permeability P_E: this index is used for reflecting the ratio that the renewable energy power generation amounts such as water energy, wind energy, solar energy in power distribution network account for gross generation, and computing formula is as follows:

$P_E=\frac{W_E}{W_{sum}}\×100\%---\left(44\right)$

In formula, W_ERepresent clean energy resource generated energy (kW h)；W_sumFor gross generation (kW h).

Further, described step (3) adopts the concrete grammar that typical case's powering mode is evaluated by Based on Entropy evaluation methodology as follows:

Step 1 determines assessment indicator system and Comment gathers

On the basis establishing index system, if Comment gathers is V={v₁,v₂,v₃,v₄,v₅}={ is outstanding, well, medium, qualified, poor }.In Comment gathers, each value represents a certain powering mode scheme index degree of membership to this comment.

Step 2 Evaluations matrix standardization

The Evaluations matrix of m scheme to be evaluated can be obtained by evaluation indice:

$C^{\′}=\left[\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ .\\ U_m\end{array}\right]=\left[\begin{array}{cccc}{c}_{11}^{\′}& c_{12}^{\′}& ...& c_{1n}^{\′}\\ c_{21}^{\′}& c_{22}^{\′}& ...& c_{2n}^{\′}\\ & ...& ...& \\ c_{m1}^{\′}& c_{m2}^{\′}& ...& c_{mn}^{\′}\end{array}\right]$

In formula, c '_ij=u_ij(i=1,2 ... m；J=1,2 ... n).

The entropy weight of step 3 agriculture products and comprehensive weight collection thereof

By normalized matrix C=[c_ij]_m×nCalculate entropy and the entropy weight of its evaluation index according to the following formula:

$H_j=-k\underset{i=1}{\overset{m}{\Σ}}{f}_{ij}{\mathrm{lnf}}_{ij},(j=1,2,...n)$

In formula, k=1/lnm,0≤H_j≤ 1, and specify to work as f_ijF when=0_ijlnf_ij=0.Correspondingly, the entropy weight of jth index is defined as:

${\mathrm{\ω}}_j=\frac{1-H_j}{n-\underset{j=1}{\overset{n}{\Σ}}{H}_j}$

In formula, 0≤ω_j≤ 1 andThe entropy weight sets that thus can obtain n evaluation index is ω={ ω₁,ω₂,…,ω_n}.The expert's subjectivity weight assuming n evaluation index is λ={ λ₁,λ₂,…λ_n, its combination with entropy weight and the comprehensive weight that obtains is:

$a_j=({\mathrm{\ω}}_j+{\mathrm{\μ\λ}}_j)/\underset{j=1}{\overset{n}{\Σ}}({\mathrm{\ω}}_j+{\mathrm{\μ\λ}}_j)$

In formula, a_jFor the comprehensive weight of jth evaluation index, μ is the subjective weight relative efficiency property coefficient for objective entropy weight, and the span of μ is set as 0.3 < μ < 3；If μ=1, represent that subjectiveness and objectiveness weight participates among comprehensive weight with identical weight.After being calculated, obtain by aggregative indicator weight vectors after comprehensive of the entropy weight of evaluation index and expert's subjectivity weight.Therefore deduce that comprehensive weight collection A={a₁,a₂,…,a_n, wherein

The fuzzy evaluating matrix of step 4 structural scheme

For m scheme to be evaluated, the evaluation indice after i-th draft norm is C_i={ c_i1,c_i2,…c_in, the membership function of V can be calculated by it by its jth index the fuzzy subset evaluated on collection V, and membership function herein is isosceles triangle membership function:

$r_{ij}\left(v_k\right)=\left\{\begin{array}{cc}\frac{c_{ij}-p_k}{q_k-p_k}& p_k\&le;c_{ij}\&le;q_k\\ \frac{s_k-c_{ij}}{s_k-q_k}& q_k\&le;c_{ij}\&le;d_k\\ 0& \end{array}\right.$

Wherein r_ij(v_k) for the jth index of i-th scheme relative to comment v_kDegree of membership, p_k,q_k,s_kFor corresponding to v_kConstant, owing to evaluation index is normalized, then take corresponding value according to 5 comments, now take q₁=0, q₂=0.25, q₃=0.5, q₄=0.75, q₅=1；For ensureing each index

At least can obtaining the degree of membership of four comments, taking isosceles triangle base is 1.6；

Thus, the fuzzy evaluating matrix that can draw i-th scheme is:

$R_i=\left[\begin{array}{cccc}{r}_{i1}\left(v_1\right)& r_{i1}\left(v_2\right)& \mathrm{...}& r_{i1}\left(v_5\right)\\ r_{i2}\left(v_1\right)& r_{i2}\left(v_2\right)& \mathrm{...}& r_{i2}\left(v_5\right)\\ & \mathrm{...}& \mathrm{...}& \\ r_{in}\left(v_1\right)& r_{in}\left(v_2\right)& \mathrm{...}& r_{in}\left(v_5\right)\end{array}\right],(i=1,2,\mathrm{...}m)$

Step 5 asks for overall merit fuzzy subset

The overall merit collection B of i-th scheme_iFor the fuzzy subset on V, calculated by following formula:

B_i=A ο R={b_i1,b_i2,b_i3,b_i4,b_i5}

Wherein A is comprehensive weight collection, R_iFor the fuzzy evaluating matrix of i-th scheme, operator ο adopts M (,+) model, then have:

$b_{ik}=\underset{j=1}{\overset{n}{\&Sigma;}}{a}_j\&CenterDot;r_{ij}\left(v_k\right),(k=1,2,3,4,5)$

To B_iIt is normalized:

${\hat{b}}_{ik}=b_{ik}/\underset{k=1}{\overset{5}{\&Sigma;}}{b}_{ik},(k=1,2,3,4,5)$

The fuzzy overall evaluation result that can obtain i-th scheme is:

${\hat{B}}_i=\{{\hat{b}}_{i1},{\hat{b}}_{i2},{\hat{b}}_{i3},{\hat{b}}_{i4},{\hat{b}}_{i5}\}$

Wherein,For the i-th scheme degree of membership relative to comment k, represent that scheme i to what extent can be described by comment k.

Step 6 utilizes fuzzy overall evaluation result that scheme is ranked up

The selection further that fuzzy overall evaluation result is network topology provides many useful informations, utilizes its information m scheme to be evaluated can be classified or be sorted.Give a score value to each comment of evaluation result and quantified, collection of can markingThe then comprehensive score of scheme iAfterwards can according to Z_iSize is ranked up.

The beneficial effects of the present invention is: compared with prior art, the invention have the advantages that the system of proposing for alternating current-direct current Distribution system design and evaluation methodology, can provide for the planning and designing of existing distribution network transform and following alternating current-direct current distribution network and effectively instruct.

Accompanying drawing explanation

Fig. 1 is the overview flow chart of the present invention.

Fig. 2 AC distribution net radial network topological structure.

Fig. 3 DC distribution net radial network topological structure.

Fig. 4 alternating current-direct current mixing power distribution network radial network topological structure.

Fig. 5 alternating current-direct current mixing power distribution network both end power supplying network topology structure.

Fig. 6 alternating current-direct current mixing power distribution network ring network topology structure.

Fig. 7 comments index valency system.

The technical evaluation index of Fig. 8.

Fig. 9 Reliability Evaluation index.

Figure 10 economic evaluation index.

The social evaluation index of Figure 11.

Figure 12 feature of environmental protection evaluation index.

Detailed description of the invention

Below in conjunction with accompanying drawing, the present invention is further elaborated.

The present invention relates to a kind of city low-voltage AC/DC distribution system planning method, specifically include that

Step one, the network topology set up under power distribution network typical case's powering mode；

Step 2, set up alternating current-direct current mixing power distribution network evaluation index system；

Typical case's powering mode is evaluated by step 3, employing Based on Entropy evaluation methodology.

Each step content is described below in detail:

The step one of the present invention:

Set up the network topology type under power distribution network typical case's powering mode and include alternating current-direct current power distribution network radial network topological structure (Fig. 1), DC distribution net radial network topological structure (Fig. 2), alternating current-direct current mixing power distribution network radial network topological structure (Fig. 3), alternating current-direct current mixing power distribution network both end power supplying network topology structure (Fig. 4), alternating current-direct current mixing power distribution network ring network topology structure (Fig. 5):

Radial AC distribution net shown in Fig. 1 is conventional powering mode, again it is powered after rectified equipment rectification is needed for DC load, the DC source such as photovoltaic generation and energy storage device passes through grid-connected inverters, there is conversion efficiency problem, and the alternating current power supply direct grid-connecteds such as wind-power electricity generation, can at utmost improve wind-powered electricity generation utilization rate；The bus of different electric pressures is coupled by transformator, and network structure is simple, and construction cost is low, but its power supply reliability is relatively low.

Radial DC distribution net shown in Fig. 2, all carries out direct current supply, the DC source direct grid-connected such as photovoltaic generation and energy storage device, can save a large amount of switch-over unit, and the alternating current power supplys such as wind-power electricity generation need to be grid-connected by commutator for all of DC load；The bus of different electric pressures can be coupled by commutator transformer, and then it need to be powered through contravariant equipment for AC load, and network transmission capacity is relatively big, and via net loss is less.

Radial alternating current-direct current mixing power distribution network shown in Fig. 3, the DC source such as photovoltaic generation and energy storage device is directly accessed DC network；Adopting AC network to power for AC load, the alternating current power supply such as wind-power electricity generation is directly accessed AC network, can be prevented effectively from rectification and power conversion losses that inversion produces；Adopting DC network to power for DC load, mixing distribution net work structure is simple, but its construction cost increases relatively.

Two ends shown in Fig. 4 power alternating current-direct current mixing power distribution network adopt dual power supply, the alternating current power supplys such as the DC source such as photovoltaic generation and energy storage device is directly accessed AC line, wind-power electricity generation are directly accessed AC line；Two ends powering mode provides Liang Tiao supply line for load, article one, serve as theme road, article one, it is extension wire, when line failure makes line switching tripping operation have a power failure, after Fault Isolation, its on-load is all or part of can be may proceed to power for load by extension wire through interconnection switch, compared with radial AC/DC network, there is higher power supply reliability and higher construction cost.

The mixing power distribution network of ring-type alternating current-direct current shown in Fig. 5, alternating current-direct current load is identical with two ends power supply mode with the access way of distribution power, compared with radial and two ends supply network, network power supply reliability improves further, wherein DC network part is circulus and ring-type operation, AC portion is circulus but open loop operation, and its construction cost is also higher accordingly.

The step 2 of the present invention:

Establish the big macroscopic evaluation system of power distribution network evaluation index five as shown in Figure 6:

Comprising again several Microscopic Indexes systems in five macro-indicators systems, below figure 7 is to shown in Figure 11:

The step 3 of the present invention: adopt Based on Entropy evaluation methodology that typical case's powering mode is evaluated, including following step:

Step 1 determines assessment indicator system and Comment gathers

On the basis establishing index system, if Comment gathers is V={v₁,v₂,v₃,v₄,v₅}={ is outstanding, well, medium, qualified, poor }.In Comment gathers, each value represents a certain powering mode scheme index degree of membership to this comment.

Step 2 Evaluations matrix standardization

The Evaluations matrix of m scheme to be evaluated can be obtained by evaluation indice:

$C^{\&prime;}=\left[\begin{array}{c}{U}_1\\ U_2\\ .\\ .\\ .\\ U_m\end{array}\right]=\left[\begin{array}{cccc}{c}_{11}^{\&prime;}& c_{12}^{\&prime;}& ...& c_{1n}^{\&prime;}\\ c_{21}^{\&prime;}& c_{22}^{\&prime;}& ...& c_{2n}^{\&prime;}\\ & ...& ...& \\ c_{m1}^{\&prime;}& c_{m2}^{\&prime;}& ...& c_{mn}^{\&prime;}\end{array}\right]$

In formula, c '_ij=u_ij(i=1,2 ... m；J=1,2 ... n).

The entropy weight of step 3 agriculture products and comprehensive weight collection thereof

By normalized matrix C=[c_ij]_m×nCalculate entropy and the entropy weight of its evaluation index according to the following formula:

$H_j=-k\underset{i=1}{\overset{m}{\&Sigma;}}{f}_{ij}{\mathrm{lnf}}_j,(j=1,2,...n)$

In formula, k=1/lnm,0≤H_j≤ 1, and specify to work as f_ijF when=0_ijlnf_ij=0.Correspondingly, the entropy weight of jth index is defined as:

${\mathrm{\&omega;}}_j=\frac{1-H_j}{n-\underset{j=1}{\overset{n}{\&Sigma;}}{H}_j}$

In formula, 0≤ω_j≤ 1 andThe entropy weight sets that thus can obtain n evaluation index is ω={ ω₁,ω₂,…,ω_n}.The expert's subjectivity weight assuming n evaluation index is λ={ λ₁,λ₂,…λ_n, its combination with entropy weight and the comprehensive weight that obtains is:

$a_j=({\mathrm{\&omega;}}_j+{\mathrm{\&mu;\&lambda;}}_j)/\underset{j=1}{\overset{n}{\&Sigma;}}({\mathrm{\&omega;}}_j+{\mathrm{\&mu;\&lambda;}}_j)$

In formula, a_jFor the comprehensive weight of jth evaluation index, μ is the subjective weight relative efficiency property coefficient for objective entropy weight, and the span of μ is set as 0.3 < μ < 3；If μ=1, represent that subjectiveness and objectiveness weight participates among comprehensive weight with identical weight.After being calculated, obtain by aggregative indicator weight vectors after comprehensive of the entropy weight of evaluation index and expert's subjectivity weight.Therefore deduce that comprehensive weight collection A={a₁,a₂,…,a_n, wherein

The fuzzy evaluating matrix of step 4 structural scheme

For m scheme to be evaluated, the evaluation indice after i-th draft norm is C_i={ c_i1,c_i2,…c_in, the membership function of V can be calculated by it by its jth index the fuzzy subset evaluated on collection V, and membership function herein is isosceles triangle membership function:

$r_{ij}\left(v_k\right)=\left\{\begin{array}{cc}\frac{c_{ij}-p_k}{q_k-p_k}& p_k\&le;c_{ij}\&le;q_k\\ \frac{s_k-c_{ij}}{s_k-q_k}& q_k\&le;c_{ij}\&le;d_k\\ 0& \end{array}\right.$

Wherein r_ij(v_k) for the jth index of i-th scheme relative to comment v_kDegree of membership, p_k,q_k,s_kFor corresponding to v_kConstant, owing to evaluation index is normalized, then take corresponding value according to 5 comments, now take q₁=0, q₂=0.25, q₃=0.5, q₄=0.75, q₅=1；For ensureing that each index at least can obtain the degree of membership of four comments, taking isosceles triangle base is 1.6；

Thus, the fuzzy evaluating matrix that can draw i-th scheme is:

$R_i=\left[\begin{array}{cccc}{r}_{i1}\left(v_1\right)& r_{i1}\left(v_2\right)& \mathrm{...}& r_{i1}\left(v_5\right)\\ r_{i2}\left(v_1\right)& r_{i2}\left(v_2\right)& \mathrm{...}& r_{i2}\left(v_5\right)\\ & \mathrm{...}& \mathrm{...}& \\ r_{in}\left(v_1\right)& r_{in}\left(v_2\right)& \mathrm{...}& r_{in}\left(v_5\right)\end{array}\right],(i=1,2,\mathrm{...}m)$

Step 5 asks for overall merit fuzzy subset

The overall merit collection B of i-th scheme_iFor the fuzzy subset on V, calculated by following formula:

B_i=A ο R={b_i1,b_i2,b_i3,b_i4,b_i5}

Wherein A is comprehensive weight collection, R_iFor the fuzzy evaluating matrix of i-th scheme, operator ο adopts M (,+) model, then have:

$b_{ik}=\underset{j=1}{\overset{n}{\&Sigma;}}{a}_j\&CenterDot;r_{ij}\left(v_k\right),(k=1,2,3,4,5)$

To B_iIt is normalized:

${\hat{b}}_{ik}=b_{ik}/\underset{k=1}{\overset{5}{\&Sigma;}}{b}_{ik},(k=1,2,3,4,5)$

The fuzzy overall evaluation result that can obtain i-th scheme is:

${\hat{B}}_i=\{{\hat{b}}_{i1},{\hat{b}}_{i2},{\hat{b}}_{i3},{\hat{b}}_{i4},{\hat{b}}_{i5}\}$

Wherein,For the i-th scheme degree of membership relative to comment k, represent that scheme i to what extent can be described by comment k.

Step 6 utilizes fuzzy overall evaluation result that scheme is ranked up

The selection further that fuzzy overall evaluation result is network topology provides many useful informations, utilizes its information m scheme to be evaluated can be classified or be sorted.Give a score value to each comment of evaluation result and quantified, collection of can markingThen scheme i's is comprehensive

ScoreAfterwards can according to Z_iSize is ranked up.

Embodiment:

The typical distribution net powering mode (Fig. 1-Fig. 5) that the present invention sets up is evaluation object.Distribution network load numerical value adopts exchange, direct current and alternating current-direct current mixing power distribution network loadtype in table 1.

Table 1 exchanges, direct current and alternating current-direct current mixing power distribution network loadtype

Obtaining each index value in index system by PSCAD emulation as shown in table 2, each index subjectivity weight is provided by expert, and objective weight adopts entropy weight weight, and comprehensive weight is respectively accounted for 0.5 weighting obtained by subjective weight and objective weight, and result is as shown in table 3.Table 2 alternating current-direct current hybrid simulation index value

Table 3 alternating current-direct current hybrid simulation index subjectivity weight

Comprehensive weight is brought in Triangleshape grade of membership function, what can obtain each alternating current-direct current mixing evaluation scheme is finally divided into 70.2,67.8,69.1,69.6,70.1, namely the assessment result quality of AC/DC network is followed successively by full direct current optimum, alternating current-direct current mixing looply connected power supply, alternating current-direct current mixing bidirectional power supply, alternating current-direct current mixing bidirectional power supply, alternating current-direct current mixing single-ended power is successively by excellent to bad, and full exchange is worst.Although it is shown that key equipment cost is higher in dc distribution network, but when DC load large percentage, no matter being that DC distribution net is respectively provided with greater advantage in line loss, the power supply reliability quality of power supply, environmental benefit etc..Although alternating current-direct current mixing distribution network has the advantage of AC and DC distribution network concurrently, but due to the complexity of its topological structure, cost of investment is of a relatively high, but its comprehensive benefit is better than AC distribution net.

Claims (4)

1. an alternating current-direct current power distribution network powering mode evaluation methodology, it is characterised in that described method comprises the steps:

(1) network topology under power distribution network typical case's powering mode is set up；

(2) alternating current-direct current mixing power distribution network evaluation index system is set up；

(3) adopt Based on Entropy evaluation methodology that typical case's powering mode is evaluated.

2. a kind of alternating current-direct current power distribution network powering mode evaluation methodology according to claim 1, it is characterised in that:

In described step (1), set up the network topology type under power distribution network typical case's powering mode and include alternating current-direct current power distribution network radial network topological structure, DC distribution net radial network topological structure, alternating current-direct current mixing power distribution network radial network topological structure, alternating current-direct current mixing power distribution network both end power supplying network topology structure and alternating current-direct current mixing power distribution network ring network topology structure.

3. a kind of alternating current-direct current power distribution network powering mode evaluation methodology according to claim 1, it is characterised in that it is specific as follows that described step (2) sets up alternating current-direct current mixing power distribution network evaluation index system:

Step one: establishing techniques evaluation index system, specifically includes herein below:

(1) network harmonic electric current content ratio α:

For AC network, network harmonic electric current content ratio is defined as the meansigma methods of the different total harmonic current content ratio of node, it may be assumed that

${\mathrm{\&alpha;}}_{AC}=\frac{\underset{i=1}{\overset{N_{AC}}{\&Sigma;}}{I}_{h,i}^{AC}/I_{0,i}^{AC}}{N_{AC}}---\left(1\right)$

In formula,For the fundamental current virtual value of AC network i-th node,For total harmonic current virtual value of AC network i-th node, N_ACFor the number of AC network node, For AC network i-th node kth (k >=0) subharmonic current virtual value；

For DC network, network harmonic electric current content ratio defines:

${\mathrm{\&alpha;}}_{DC}=\frac{\underset{i=1}{\overset{N_{DC}}{\&Sigma;}}{I}_{h,i}^{DC}/I_{0,i}^{DC}}{N_{DC}}---\left(2\right)$

In formula,For the fundamental current virtual value of DC network i-th node,For total harmonic current virtual value of DC network i-th node, N_DCFor the number of DC network node, For DC network i-th node kth (k >=0) subharmonic current virtual value；

(2) network average voltage aberration rate ξ_avg: electric power distribution network average voltage aberration rate represents with the meansigma methods of different voltage node voltage distortion rate, it may be assumed that

${\mathrm{\&xi;}}_{avg}=\frac{\underset{i=1}{\overset{N_V}{\&Sigma;}}{\mathrm{\&xi;}}_i}{N_V}\left(3\right)$

In formula, N_VFor the nodes of the DC network of AC network, ξ_iFor the voltage distortion rate of node i, can represent with the percent of the root-mean-square value of this node each harmonic voltage with the ratio of fundamental voltage virtual value, it may be assumed that

${\mathrm{\&xi;}}_i=\sqrt{\frac{U_{i,2}^2+U_{i,3}^2+U_{i,4}^2+\mathrm{...}+U_{i,n}^2}{U_{i,1}^2}}\&times;100\%---\left(4\right)$

In formula, U_i,2,U_i,3,…,U_i,nRepresent each harmonic voltage of node i；For AC network, U_i,1Represent the fundametal compoment of node i, and for DC network, U_i,1Represent the DC component of node i；

(3) amplitude, ao U on average drops in network voltage temporarily:

It is network voltage on average temporary range of decrease degree by the mean value definition of temporary for each node voltage range of decrease degree；

For AC network, the voltage dip amplitude of arbitrary node represents with rated voltage root-mean-square value with the root-mean-square value dropping voltage temporarily, it may be assumed that

${\mathrm{\&Delta;U}}_{AC}=\frac{\underset{i=1}{\overset{N_{AC}}{\&Sigma;}}{U}_{i-rms1}/U_{i-rms2}}{N_{AC}}---\left(5\right)$

In formula, U_i-rms1The virtual value of voltage, U drop temporarily for node i_i-rms2For node i rated voltage virtual value；

For DC network, arbitrary node is defined as the ratio dropping busbar voltage temporarily with specified busbar voltage, it may be assumed that

${\mathrm{\&Delta;U}}_{DC}=\frac{\underset{i=1}{\overset{N_{DC}}{\&Sigma;}}{U}_{i-dc}/U_{i-dc}}{N_{DC}}---\left(6\right)$

In formula, U_i-dcFor node i, busbar voltage, U drop temporarily_i-dcSpecified busbar voltage for node i；

(4) the average departure degree d of network voltage:

For AC network, the average departure degree of network voltage is defined as the meansigma methods of each node voltage irrelevance；

For AC network:

$d_{AC}=\frac{\underset{i=1}{\overset{N_{AC}}{\&Sigma;}}{d}_{AC,i}}{N_{AC}}---\left(7\right)$

In formula, d_AC,iVoltage deviation degree for AC network node:

$d_{AC,i}=\frac{(U_{rated-ac,i}-U_{load-ac,i})}{U_{rated-ac,i}}\&times;100\%---\left(8\right)$

In formula, U_rated-acFor the rated voltage of AC network node i, U_load-acVirtual voltage during load is accessed for AC network node i；

For DC network:

$d_{DC}=\frac{\underset{i=1}{\overset{N_{DC}}{\&Sigma;}}{d}_{DC,i}}{N_{DC}}---\left(9\right)$

In formula, d_DC,iVoltage deviation degree for DC network node i:

$d_{DC,i}=\frac{(U_{rated-dc,i}-U_{load-dc,i})}{U_{rated-dc,i}}\&times;100\%---\left(10\right)$

In formula, U_rated-dc,iFor DC network node i rated voltage, U_load-dcVirtual voltage during load is accessed for DC network node i；

(5) network line loss Δ P:

Network line loss is defined as each line loss sum:

$\mathrm{\&Delta;}P=\underset{l=1}{\overset{N_L}{\&Sigma;}}(P_{from,l}-P_{to,l})---\left(11\right)$

In formula, P_from,P_toRespectively l article of direct current of power distribution network or alternating current circuit head end and end active power；N_LFor power distribution network direct current and alternating current circuit sum；

(6) network average line pressure drop Δ U^L:

The meansigma methods that network average line pressure drop is defined as in network all line drops；

For AC distribution net:

${\mathrm{\&Delta;U}}_{AC}^L=\frac{\underset{l=1}{\overset{N_{ACL}}{\&Sigma;}}{\mathrm{\&Delta;U}}_{AC,l}}{N_{ACL}}---\left(12\right)$

${\mathrm{\&Delta;U}}_{AC,l}\&ap;\frac{P_{AC}{R}_{AC}+Q_{AC}{X}_{AC}}{U_{AC}}---\left(13\right)$

In formula, P_AC、Q_ACRespectively line end active power and reactive power；R_AC、X_ACRespectively line equivalent resistance and equivalent reactance；U_ACFor line end node voltage virtual value；N_ACLFor alternating current circuit sum；

For DC distribution net, network average line pressure drop is defined as:

${\mathrm{\&Delta;U}}_{DC}^L=\frac{\underset{l=1}{\overset{N_{DCL}}{\&Sigma;}}{\mathrm{\&Delta;U}}_{DC,l}}{N_{DCL}}---\left(14\right)$

${\mathrm{\&Delta;U}}_{DC,l}\&ap;\frac{P_{DC}{R}_{DC}}{U_{DC}}---\left(15\right)$

In formula, P_DCFor DC line end active power；R_DCEquivalent resistance for direct current cables；U_DCFor DC line endpoint node voltage；N_DCLFor DC line sum；

(7) the temporary frequency reducing of network voltage time N_F: the voltage dip frequency refers to the number of times that in certain time, voltage dip occurs, and its numerical value is more high then more high on the frequent degree of the impact of sensitive load, and the voltage dip frequency method of estimation based on user satisfaction is as follows:

$N_F=\underset{l=1}{\overset{N_L}{\&Sigma;}}{\mathrm{\&delta;}}_l{L}_l---\left(16\right)$

In formula, δ_l、L_lRespectively the fault rate of l article of circuit and this circuit are in the length in dissatisfied region；

(8) the stability K of network bus voltage_V: the average stability of all nodes in this index expression network, adopt maximum loadability as the voltage stability margin of system, adopt power margin index K_VReflect the power [11] of node:

$K_V=\frac{\underset{i=1}{\overset{N_V}{\&Sigma;}}{K}_{V,i}}{N_V}---\left(17\right)$

$K_{V,i}=\frac{P_{cr,i}-P_{o,i}}{P_{o,i}}---\left(18\right)$

In formula, P_cr,iPower limit for node i；P_o,iOperation power for node i；Due to the problem that DC network is absent from busbar voltage stability, it is believed that K_V=1；

(9) " N-1 " can turn for rate:

" N-1 " can turn the rate of confession and refer to that power distribution network is when losing 1 element, turns the ratio accounting for total load for load:

${\mathrm{\&alpha;}}_{N-1}=\frac{\underset{i=1}{\overset{N_V}{\&Sigma;}}{P}_{rec1,i}}{\underset{i=1}{\overset{N_V}{\&Sigma;}}{P}_{load,i}}\&times;100\%---\left(19\right)$

In formula, P_rec1,iFor there is the load power of " N-1 " fault posterior nodal point i；P_load,iLoad power for the front nodal point i that breaks down；

(10) " N-2 " can turn for rate:

" N-2 " can turn the rate of confession and refer to that power distribution network is when losing 2 elements, turns the ratio accounting for total load for load:

${\mathrm{\&alpha;}}_{N-2}=\frac{\underset{i=1}{\overset{N_V}{\&Sigma;}}{P}_{rec2,i}}{\underset{i=1}{\overset{N_V}{\&Sigma;}}{P}_{load,i}}\&times;100\%---\left(20\right)$

In formula, P_rec2,iFor there is the load power of " N-2 " fault posterior nodal point i；

(11) line efficiency γ_E:

Refer to when electrical network is in peak load running status, the ratio of apparatus of load and equipment rated capacity, it is mainly used in quantifying the loading condition of equipment in electrical network:

${\mathrm{\&gamma;}}_E=\underset{1\&le;l\&le;N_L}{min}{\mathrm{\&gamma;}}_{L,l}---\left(21\right)$

${\mathrm{\&gamma;}}_{L,l}=\frac{P_{from,l}}{P_{L,l}^{\max }}---\left(22\right)$

In formula, γ_L,lIt is the load factor of l article of circuit, the i.e. utilization rate of l article of circuit；Maximum transfer capacity for circuit；

(12) power autonomous user's ratio such as distributed power generation, energy storage: this index expression distributed power source and energy storage device generated energy be the ratio in institute's power consumption in customer charge, defines as follows:

$D_d=\frac{W_{dis-sto}}{W_{load}}\&times;100\%---\left(23\right)$

In formula, W_dis-stoThe electricity (kW h) of customer charge is supplied for distributed power source and energy storage device；W_loadFor customer charge power consumption (kW h)；

Step 2: set up Reliability Evaluation system, specifically include herein below:

(1) mean failure rate frequency of power cut in SAIFI: one year total frequency of power cut divided by total number of users (secondary/user's year)；

$SAIFI=\frac{\underset{j=1}{\overset{N_C}{\&Sigma;}}{N}_j^{US}}{N_C}---\left(24\right)$

In formula, N_CFor total number of users；For the frequency of power cut in user j 1 year；

(2) user's System average interruption duration average power off time of each user in SAIDI: a year；

$SAIDI=\frac{\underset{j=1}{\overset{N_C}{\&Sigma;}}{T}_j}{N_C}---\left(25\right)$

In formula, T_jTotal time is continued for having a power failure in user j 1 year；

(3) the power supply reliability power supply hourage that in ASAI: a year, the hourage that do not have a power failure of user requires altogether divided by user；

$ASAI=\frac{T_h\&times;N_C-\underset{j=1}{\overset{N_C}{\&Sigma;}}{T}_j}{T_h\&times;N_C}---\left(26\right)$

In formula, T_hRepresent stipulated time domestic demand electricity hourage, for instance within 1 year, be unit, general T_h=8760；

(4) system total electricity deficiency index ENS: system in 1 year because having a power failure and causing the total electric quantity loss of user；

$ENS=\underset{i=1}{\overset{N_C}{\&Sigma;}}{E}_{loss,i}---\left(27\right)$

In formula, E_loss,iFor user's electric quantity loss that i & lt power failure causes；

(5) average power off time CAIDI: the System average interruption duration of fault outage every time；

$CAIDI=\frac{\underset{j=1}{\overset{N_C}{\&Sigma;}}{T}_j}{\underset{j=1}{\overset{N_C}{\&Sigma;}}{N}_j^{US}}---\left(28\right)$

Above-mentioned power supply reliability index all according to the fault rate of power distribution network distinct device, can adopt Monte Carlo simulation method to be calculated；

(6) the continued power time CT of specific investment cost

The reflection of this index increases or keeps in repair the investment of the circuit/distributed power source/energy storage device contribution to reliability newly, newly-increased or maintenance of equipment all can reduce the fault rate of relevant device, therefore this refers to that target value is more big, then it represents that the contribution degree improving distribution network reliability is more big；This index has an appreciable impact for the radial electrical distribution net providing high power supply reliability relatively low, and less for power distribution network contribution degree that reliability is higher；

$C_T=\underset{1\&le;i\&le;N_{EC}}{min}\frac{T_h\&times;A_{SAI,i}}{C_{R,i}}---\left(29\right)$

In formula, N_ECFor the device type sum in network；A_SAI,iThe power supply reliability of power distribution network after representing newly-increased or safeguarding the i-th kind equipment；C_R,iRepresent newly-increased or maintenance the i-th kind equipment cost:

C_R,i=N_AM,i·(a_EC,i+w_EC,i)(30)

In formula, N_AM,iFor newly-increased or maintenance device type sum；a_EC,iIt it is the unit price of the i-th kind equipment；w_EC,iIt is the unit maintenance cost of the i-th kind equipment, when renewal of the equipment, makes w_EC,i=0, when maintenance of equipment, make a_EC,i=0；

(7) the power supply capacity index GP of specific investment cost

This index expression increases the investment of the transformator/circuit/distributed power source/energy storage device contribution degree to power distribution network power supply capacity newly, and the value of this index is more big, it was shown that specific investment cost is more notable to the raising of power distribution network power supply capacity；

$G_P=\underset{1\&le;i\&le;N_{EC}}{min}\frac{C_{P,i}}{C_{I,i}}---\left(31\right)$

In formula, C_P,iRepresent the minima of every kind equipment rated capacity sum after increasing i kind equipment:

$C_{P,i}=\underset{1\&le;i\&le;N_{EC}}{min}\underset{k=1}{\overset{N_{EC,i}}{\&Sigma;}}{P}_{i,k}^{\max }---\left(32\right)$

In formula, N_EC,iIt it is the sum of the i-th kind equipment；It it is the rated capacity of kth equipment in the i-th kind equipment；

C_I,iRepresent the cost of investment of newly-increased i-th kind equipment:

C_I,i=N_add,ia_EC,i(33)

In formula, N_add,iRepresent the quantity being increased by the i-th kind equipment；

The step 3 of the present invention: set up economic evaluation index system, specifically include herein below

(1) equipment investment cost index S_AC/DC

The equipment investment of distribution network planning construction specifically includes that direct current cables and ac cable investment, user's side inverter and commutator investment, exchange, commutator transformer investment^,, exchange, dc circuit breaker investment, middle pressure current conversion station (VSC) investment etc.；

For AC network, not including middle pressure current conversion station in equipment investment, user side does not include contravariant equipment, and the computational methods of equipment investment are as follows:

$S_{AC/DC}=\underset{i=1}{\overset{N_{Eac}}{\&Sigma;}}{N}_{ac,i}{a}_{ac,i}.---\left(34\right)$

In formula, N_Eac,iIt is the number of units of i-th kind of alternating current equipment, a_Eac,iFor the unit price of in AC network i-th kind of equipment, N_EacRequired alternating current equipment type sum is built for AC network；

For DC network, network does not have AC transformer, user side do not have the rectifying installation, equipment investment computational methods to be:

$S_{AC/DC}=\underset{i=1}{\overset{N_{Edc}}{\&Sigma;}}{N}_{dc,i}{a}_{dc,i}---\left(35\right)$

In formula, N_Edc,iIt is the number of units of i-th kind of DC equipment, a_Edc,iFor the unit price of in DC network i-th kind of equipment, N_EdcRequired alternating current equipment type sum is built for DC network；

For alternating current-direct current mixing power distribution network, computational methods ibid, simply include all of key equipment；

(2) equipment depreciation expense D_C:

$D_C=\underset{i=1}{\overset{N_{EC}}{\&Sigma;}}{D}_{C_i}---\left(36\right)$

In formula,It is the yearly depreciation charge of the i-th kind equipment:

$D_{C_i}=S_{B,i}\&CenterDot;r_{C,i}---\left(37\right)$

In formula, S_B,iIt is the i-th kind equipment initial investment, r_C,iIt is the yearly depreciation of the i-th kind equipment, r_C,i=(1-λ_i)/N_Y, λ_iIt is the net salvage of the i-th kind equipment, N_YIt it is the depreciable life of the i-th kind equipment；

(3) effective power supply rate E of specific investment cost_R

This index reflects the investment of the newly-increased transformator/circuit/distributed power source/energy storage device/reactive power compensator percentage contribution to reducing distribution network line loss, E_RValue is more big, it was shown that invest the effect to reducing line loss more obvious；

$E_R=\underset{1\&le;i\&le;N_{EC}}{min}\frac{{\mathrm{\&Delta;A}}_i\%}{C_{I,i}}---\left(38\right)$

${\mathrm{\&Delta;A}}_i\%=\frac{{\mathrm{\&Delta;W}}_i}{W_S}\&times;100\%---\left(39\right)$

In formula, Δ A_i% is the line loss per unit after newly-increased i-th kind equipment；ΔW_iThe variable quantity (kW h) of line loss during more non-newly added equipment after expression newly added equipment；W_STotal delivery (kW h) of all power supplys (containing energy storage device) before representing non-newly added equipment；For DC network, reactive-load compensation equipment number of units is 0；

(4) specific investment cost greatest expected electricity sales amount E_P

This index is reflected under specific investment cost, and power distribution network can be supplied to the maximum electricity of user in 1 year, this refers to that target value is more big, and specific investment cost is to E_PContribution degree more high；

$E_P=\frac{E_{\max }}{C_E}---\left(40\right)$

In formula, C_EFor electrical network gross investment, $C_E=S_{AC/DC}+D_C++\underset{k=1}{\overset{N_{add,i}}{\&Sigma;}}(C_{R,i}+C_{I,i}+C_{L,i}),$ Reflect the investment corresponding to influence factor such as power supply capacity, power supply reliability, line loss, i.e. cost；E_maxFor electrical network greatest expected electricity sales amount:

$E_{max}=T_h\&times;N_C\&times;A_{SAI}\&times;\underset{j=1}{\overset{N_C}{\&Sigma;}}{P}_{load,j}---\left(41\right)$

In formula, P_load,jAverage active power for user j；

The step 4 of the present invention: set up social evaluation index system, specifically include herein below

With user, the comprehensive score of satisfaction of electrical network is reflected the social benefit of power distribution network, the present invention ask for the process of index adopts herein expert to point mode, every kind of powering mode is carried out to dividing with the angle of user satisfaction；From power supply quality, Standard Service, consultancy service, the electricity charge are paid, 5 aspects of Service Management are evaluated, the full marks of every aspect are 100 points, minimum are divided into 0 point, and analog subscriber is averaged after 5 aspects are given a mark, pass through membership function, meansigma methods is carried out as user satisfaction after obfuscation, further according to the weight of each user, obtains the comprehensive score of user satisfaction:

$G_C=\underset{j=1}{\overset{N_C}{\&Sigma;}}{\mathrm{\&omega;}}_{C,j}{f}_{C,j}---\left(42\right)$

In formula, ω_C,jFor user's j satisfaction weight, f_C,jFor fuzzy membership angle value；

The step 5 of the present invention: set up feature of environmental protection evaluation index system, specifically include herein below

(1) carbon emission reduction amount: thermal power generation sends the discharge capacity of carbon dioxide that corresponding green energy resource generated energy discharges, is generally adopted following formula and calculates:

$E_{{\mathrm{co}}_2}=0.4kg/kwh*2.493*W_g---\left(43\right)$

In formula, W_gFor green energy resource generated energy, unit (kW h)；

(2) clean energy resource permeability P_E: this index is used for reflecting the ratio that the renewable energy power generation amounts such as water energy, wind energy, solar energy in power distribution network account for gross generation, and computing formula is as follows:

$P_E=\frac{W_E}{W_{sum}}\&times;100\%---\left(44\right)$

In formula, W_ERepresent clean energy resource generated energy (kW h)；W_sumFor gross generation (kW h).

4. a kind of alternating current-direct current power distribution network powering mode evaluation methodology according to claim 1, it is characterised in that described step (3) adopts the concrete grammar that typical case's powering mode is evaluated by Based on Entropy evaluation methodology as follows:

Step 1 determines assessment indicator system and Comment gathers

On the basis establishing index system, if Comment gathers is V={v₁,v₂,v₃,v₄,v₅}={ is outstanding, well, medium, qualified, poor }；In Comment gathers, each value represents a certain powering mode scheme index degree of membership to this comment；

Step 2 Evaluations matrix standardization

The Evaluations matrix of m scheme to be evaluated can be obtained by evaluation indice:

$C^{\&prime;}=\left[\begin{array}{c}{U}_1\\ U_2\\ \&CenterDot;\\ \&CenterDot;\\ \&CenterDot;\\ U_m\end{array}\right]=\left[\begin{array}{cccc}{c}_{\mathrm{11}}^{\&prime;}& c_{\mathrm{12}}^{\&prime;}& ...& c_{\mathrm{1n}}^{\&prime;}\\ c_{\mathrm{21}}^{\&prime;}& c_{22}^{\&prime;}& ...& c_{2n}^{\&prime;}\\ & ...& ...& \\ c_{\mathrm{m1}}^{\&prime;}& c_{\mathrm{m2}}^{\&prime;}& ...& c_{mn}^{\&prime;}\end{array}\right]$

In formula, c '_ij=u_ij(i=1,2 ... m；J=1,2 ... n)；

The entropy weight of step 3 agriculture products and comprehensive weight collection thereof

By normalized matrix C=[c_ij]_m×nCalculate entropy and the entropy weight of its evaluation index according to the following formula:

$H_j=-k\underset{i=1}{\overset{m}{\&Sigma;}}{f}_{ij}{\inf }_{ij},(j=1,2,...n)$

In formula, k=1/lnm,0≤H_j≤ 1, and specify to work as f_ijF when=0_ijlnf_ij=0；Correspondingly, the entropy weight of jth index is defined as:

${\mathrm{\&omega;}}_j=\frac{1-H_j}{n-\underset{j=1}{\overset{n}{\&Sigma;}}{H}_j}$

In formula, 0≤ω_j≤ 1 andThe entropy weight sets that thus can obtain n evaluation index is ω={ ω₁,ω₂,…,ω_n}；The expert's subjectivity weight assuming n evaluation index is λ={ λ₁,λ₂,…λ_n, its combination with entropy weight and the comprehensive weight that obtains is:

$a_j=({\mathrm{\&omega;}}_j+{\mathrm{\&mu;\&lambda;}}_j)/\underset{j=1}{\overset{n}{\&Sigma;}}({\mathrm{\&omega;}}_j+{\mathrm{\&mu;\&lambda;}}_j)$

In formula, a_jFor the comprehensive weight of jth evaluation index, μ is the subjective weight relative efficiency property coefficient for objective entropy weight, and the span of μ is set as 0.3 < μ < 3；If μ=1, represent that subjectiveness and objectiveness weight participates among comprehensive weight with identical weight；After being calculated, obtain by aggregative indicator weight vectors after comprehensive of the entropy weight of evaluation index and expert's subjectivity weight；Therefore deduce that comprehensive weight collection A={a₁,a₂,…,a_n, wherein

The fuzzy evaluating matrix of step 4 structural scheme

For m scheme to be evaluated, the evaluation indice after i-th draft norm is C_i={ c_i1,c_i2,…c_in, the membership function of V can be calculated by it by its jth index the fuzzy subset evaluated on collection V, and membership function herein is isosceles triangle membership function:

$r_{ij}\left(v_k\right)=\left\{\begin{array}{cc}\frac{c_{ij}-p_k}{q_k-p_k}& p_k\&le;c_{ij}\&le;q_k\\ \frac{s_k-c_{ij}}{s_k-q_k}& q_k\&le;c_{ij}\&le;d_k\\ 0& \end{array}\right.$

Wherein r_ij(v_k) for the jth index of i-th scheme relative to comment v_kDegree of membership, p_k,q_k,s_kFor corresponding to v_kConstant, owing to evaluation index is normalized, then take corresponding value according to 5 comments, now take q₁=0, q₂=0.25, q₃=0.5, q₄=0.75, q₅=1；For ensureing that each index at least can obtain the degree of membership of four comments, taking isosceles triangle base is 1.6；

Thus, the fuzzy evaluating matrix that can draw i-th scheme is:

$R_i=\left[\begin{array}{cccc}{r}_{i1}\left(v_1\right)& r_{i1}\left(v_2\right)& ...& r_{i1}\left(v_5\right)\\ r_{i2}\left(v_1\right)& r_{i2}\left(v_2\right)& ...& r_{i2}\left(v_5\right)\\ & ...& ...& \\ r_{in}\left(v_1\right)& r_{in}\left(v_2\right)& ...& r_{in}\left(v_5\right)\end{array}\right],(i=1,2,...m)$

Step 5 asks for overall merit fuzzy subset

The overall merit collection B of i-th scheme_iFor the fuzzy subset on V, calculated by following formula:

B_i=A o R={b_i1,b_i2,b_i3,b_i4,b_i5}

Wherein A is comprehensive weight collection, R_iFor the fuzzy evaluating matrix of i-th scheme, operator o adopts M (,+) model, then have:

$b_{ik}=\underset{j=1}{\overset{n}{\&Sigma;}}{a}_j\&CenterDot;r_{ij}\left(v_k\right),(k=1,2,3,4,5)$

To B_iIt is normalized:

${\hat{b}}_{ik}=b_{ik}/\underset{k=1}{\overset{5}{\&Sigma;}}{b}_{ik},(k=1,2,3,4,5)$

The fuzzy overall evaluation result that can obtain i-th scheme is:

${\hat{B}}_i=\{{\hat{b}}_{i1},{\hat{b}}_{i2},{\hat{b}}_{i3},{\hat{b}}_{i4},{\hat{b}}_{i5}\}$

Wherein,For the i-th scheme degree of membership relative to comment k, represent that scheme i to what extent can be described by comment k；

Step 6 utilizes fuzzy overall evaluation result that scheme is ranked up

The selection further that fuzzy overall evaluation result is network topology provides many useful informations, utilizes its information m scheme to be evaluated can be classified or be sorted；Give a score value to each comment of evaluation result and quantified, collection of can markingThe then comprehensive score of scheme iAfterwards can according to Z_iSize is ranked up.