CN105048521A - Method for calculating direct current access capability of receiving end power grid with consideration of multiple constraints - Google Patents

Abstract

The invention discloses a method for calculating direct current access capability of a receiving end power grid with consideration of multiple constraints, belonging to the technical field of electric power system and automation thereof. The method for calculating direct current access capability of a receiving end power grid with consideration of multiple constraints comprises: determining an alternative direct current drop point set according to the station address condition of a transformer station, electric power balance and the like; determining newly increased direct current access drop points according to the short circuit capacity of each alternative direct current drop point in the typical mode and the interaction degree between each direct current in the typical mode; and giving the direct current access capability of a receiving end power grid through iteration after integrated consideration of multiple constraints comprising the direct current multi-infeed short circuit ratio, the power grid low ebb peak load regulation capacity, the relative moment of inertia index, the N-1 transient stability and the like. The method for calculating direct current access capability of a receiving end power grid with consideration of multiple constraints is beneficial to guidance of a power grid planning department about reasonable planning of the direct current drop points of the receiving end power grid, and can give the reasonable level for the direct current access capability of the receiving end power grid and reduce the blindness for direct current construction, and can improve the power grid operation control level.

Description

A kind of receiving end electrical network direct current access capability computational methods considering multiple constraint

Technical field

The invention belongs to Power System and its Automation technical field, more precisely, the present invention relates to a kind of receiving end electrical network direct current access capability computational methods considering multiple constraint.

Background technology

High voltage direct current (HVDC) transmission of electricity has become the important form of the interconnected and long-distance and large-capacity power transmission of domestic great Qu with the advantage of its uniqueness, for the large-scale most optimum distribution of resources of China has played important function.Along with the development construction of electrical network, multiple-circuit line transmission line drop point same interchange receiving end electrical network is inevitable, and south electric network and East China Power Grid have developed into typical direct current many feed-ins receiving end electrical network all, and direct current feed-in capacity constantly increases.

In order to instruct power grid construction better and safeguard receiving end electricity net safety stable, a key issue must be researched and solved, namely the ability that receiving end electrical network accepts direct current feed-in power how is assessed, what comprise electrical network to allow the power total amount of feed-in and maximum single feedback of permission to enter capacity how to determine, principle should be followed and select direct current drop point effectively could improve the direct current of receiving end electrical network by power etc.These problems have become key technical problem urgently to be resolved hurrily in bulk power grid planning and design.Affect electrical network direct current a lot of by the factor of power, in the production run of actual electric power, the transient state dynamic stability characteristic, many direct currents alternating current-direct current reciprocal effect characteristic etc. of the voltage stabilization of the low ebb peak modulation capacity of electrical network, the trend evacuation capacity of direct current near region, partial electric grid, system frequency safety, electrical network, all can cause restriction to the direct current access capability of electrical network.

At present about the research of the maximum powered scale of receiving end electrical network direct current is less, mostly Patents is the optimum choice about direct current drop point, and considers that constraint is relatively less.Patent " a kind of system of selection of receiving end electrical network direct current drop point " (application number CN201410239756.1) discloses the system of selection of a kind of direct current drop point, main considers short circuit ratio and steady characteristic two stability indicators and power grid construction cost and via net loss cost two economic indexs temporarily.Different direct current access scheme is considered on the impact in direct-current commutation failure region in the optimization direct current drop point method that patent " a kind of direct current of optimizing concentrates the method for feed-in receiving-end system direct current drop point " (application number CN201310545965.4) proposes.Patent " a kind of multi-feed HVDC system of selection based on many feed-ins short circuit ratio " (authorizing, CN201210081310.1) selects preferably direct current synchronizing point by the calculating to different direct current synchronizing point many feed-ins short circuit ratio, process, analysis.Patent " a kind of computational methods exchanging the powered scale of receiving end electrical network direct current " (application number CN201410104305.7) proposes a kind of computational methods exchanging the powered scale of receiving end electrical network direct current, the method only considers that direct current many feed-ins short circuit ratio retrains, and can not meet operation of power networks control overflow completely.

Summary of the invention

The object of the invention is: the ability accepting direct current feed-in in order to assess receiving end electrical network, improving alternating current-direct current series-parallel connection bulk power grid operation and management level, providing a kind of receiving end electrical network direct current access capability computational methods considering multiple constraint.The method determines alternative direct current drop point set according to substation location condition, power balance etc., according to the reciprocation degree between the capacity of short circuit of alternative direct current drop point each under typical way and each direct current, determine newly-increased direct current access drop point, consider direct current many feed-ins short circuit ratio, electrical network low ebb peak modulation capacity, relatively rotate the multi-constraint condition such as inertia index, N-1 transient stability, iteration provides the direct current access capability of receiving end electrical network.

Specifically, the present invention adopts following technical scheme to realize, and comprises the following steps:

1, consider receiving end electrical network direct current access capability computational methods for multiple constraint, comprise the steps:

1-1) determine rack based on a certain, note has wherein accessed M bar direct current, and the capacity of every bar direct current is respectively P _d,i(i=1,2 ..., M), form typical operation modes, the equal full capacity power transmission of M bar direct current wherein accessed, determines alternative direct current drop point set according to substation location condition, power balance etc., supposes total N number of alternative direct current drop point;

1-2) according to the reciprocation degree between the capacity of short circuit of alternative direct current drop point each under typical way and each direct current, determine newly-increased direct current access drop point, the initial capacity of new access direct current is designated as P _new(P _newrelevant with DC voltage level, ± 500kV is generally 3000MW, and ± 800kV is generally 8000MW, and ± 1000kV is generally 10000MW, and giving tacit consent to initial access capacity in this step is 8000MW).

1-3) utilize 1-2) in obtained direct current drop point, set up new power system operating mode data, original access direct current transmission power remains unchanged, newly-increased D.C. capacity P _new;

1-4) calculate the effective short circuit ratio MESCR of many feed-ins of all M+1 bar direct currents _i(i=1,2 ..., M+1), if the effective short circuit ratio of many feed-ins of all direct currents is all greater than a certain threshold value R _ref(according to pertinent literature, R _refgenerally get 2-2.5), carry out 1-5), otherwise carry out 1-6);

1-5) check electrical network low ebb peak modulation capacity, relatively rotate inertia index, N-1 transient stability, if all satisfy condition, make M=M+1, return 1-1), otherwise carry out 1-8);

1-6) reduce the direct current transmission power P of new access _ad(P _adfor the direct current power adjustment step-length set according to acceptable error, as desirable 100MW), make P _new=P _new-P _ad, form new operational mode, calculate the effective short circuit ratio of many feed-ins of all direct currents, if the effective short circuit ratio of many feed-ins that still there is direct current is less than R _ref, return 1-6), otherwise carry out 1-7);

1-7) check electrical network low ebb peak modulation capacity, relatively rotate inertia index, N-1 transient stability, if meet institute's Constrained, then carry out 1-9), otherwise carry out 1-8)

1-8) reduce the direct current transmission power P of new access _ad, make P _new=P _new-P _ad, form new operational mode, check electrical network low ebb peak modulation capacity, relatively rotate inertia index, N-1 transient stability, if meet institute's Constrained, carry out 1-9), otherwise return 1-8);

Direct current access capability 1-9) calculating receiving end electrical network is

Technique scheme is further characterized in that, described step 1-2) according to the reciprocation degree between the capacity of short circuit of alternative direct current drop point each under typical way and each direct current, determine newly-increased direct current access drop point, its concrete grammar and step as follows:

The effective short circuit ratio MSCR of many feed-ins of the M bar direct current accessed under 2-1) calculating typical way _i(i=1,2 ..., M), remember that the minimum direct current of the effective short circuit ratio of many feed-ins is numbered NUM;

The capacity of short circuit S of N number of alternative direct current drop point under 2-2) calculating typical way _{ac, j}(j=1,2 ..., N), remember that wherein capacity of short circuit maximum is S _acmax, capacity of short circuit minimum value is S _acmin, obtain the capacity of short circuit index S of a jth alternative direct current drop point _j,

$S_j=\frac{S_{\mathrm{ac},j}-S_{\mathrm{ac}\min }}{S_{\mathrm{ac}\max }-S_{\mathrm{ac}\min }},j=\mathrm{1,2},...,N---\left(1\right);$

2-3) to jth alternative direct current drop point, the equivalent impedance Z between the drop point calculating itself and original access direct current _{eq, mn}(m, n=1,2 ..., M, M+1; M+1 represents in the jth direct current that direct current drop point newly an accesses numbering), calculate new access direct current to the influence degree index A of original access direct current according to equivalent impedance and direct current access capacity _j, new access direct current is to the influence degree index B of the weakest direct current _j, all direct currents that accessed are to the new influence degree index C accessing direct current _j, shown in it is calculated as follows,

$\left\{\begin{array}{c}{A}_{j,\mathrm{eq}}=\underset{i=1}{\overset{M}{\mathrm{\Σ}}}\frac{\left|Z_{\mathrm{eq},i(M+1)}\right|P_{\mathrm{new}}}{\left|Z_{\mathrm{eq},\mathrm{ii}}\right|P_{d,i}}\\ B_{j,\mathrm{eq}}=\frac{\left|Z_{\mathrm{eq},\left(\mathrm{NUM}\right)(M+1)}\right|P_{\mathrm{new}}}{\left|Z_{\mathrm{eq},\left(\mathrm{NUM}\right)\left(\mathrm{NUM}\right)}\right|P_{d,i}}\\ C_{j,\mathrm{eq}}=\underset{i=1}{\overset{M}{\mathrm{\Σ}}}\frac{\left|Z_{\mathrm{eq},(M+1)i}\right|P_{d,i}}{\left|Z_{\mathrm{eq},(M+1)(M+1)}\right|P_{\mathrm{new}}}\end{array}\right.---\left(2\right)$

To all N number of alternative direct current drop points, note

A _max＝max{A _1,eq,A _2,eq,...,A _N,eq,}，A _min＝min{A _1,eq,A _2,eq,...,A _N,eq,}

B _max＝max{B _1,eq,B _2,eq,...,B _N,eq,}，B _min＝min{B _1,eq,B _2,eq,...,B _N,eq,}

C _max＝max{C _1,eq,C _2,eq,...,C _N,eq,}，C _min＝min{C _1,eq,C _2,eq,...,C _N,eq,}

Carry out standardization to index can obtain,

$\left\{\begin{array}{c}{A}_j=\frac{A_{\max }-A_{j,\mathrm{eq}}}{A_{\max }-A_{j,\min }}\\ B_j=\frac{B_{\max }-B_{j,\mathrm{eq}}}{B_{\max }-B_{j,\min }}\\ C_j=\frac{C_{\max }-C_{j,\mathrm{eq}}}{C_{\max }-C_{j,\min }}\end{array}\right.---\left(3\right)$

2-4) calculate and obtain when selecting jth alternative direct current drop point, influence each other between new access direct current and each direct current of original access level index

$I_j=\frac{1}{3}(A_j+B_j+C_j)---\left(4\right)$

Direct current drop point selective goal under 2-5) adopting linear weighted function summation approach to obtain a jth alternative direct current drop point,

LD _j＝λ ₁S _j+λ ₂I _j(5)

Wherein weight coefficient meets λ ₁+ λ ₂the constraint of=1, can adopt the method such as capacitive equipments, ranking method to obtain, and for the purpose of simple, can make λ ₁=λ ₂=0.5, the maximum drop point of selective goal value is as newly-increased direct current drop point.

Technique scheme is further characterized in that, described step 1-5) lieutenant colonel's nuclear power net low ebb peak modulation capacity, relatively rotate inertia index, N-1 transient stability, its concrete grammar and step as follows:

5-1) check electrical network low ebb peak modulation capacity and adopt following index,

η _tr＝P _Ltr-P _Gmin-P _Gfc+P _Gps-P _Dtr-P _Grn(6)

Wherein η _trfor electrical network low ebb peak regulation nargin, if η _tr>=0 illustrates that electrical network low ebb peak modulation capacity meets constraint, η _tr< 0 illustrates that electrical network low ebb peak modulation capacity does not meet constraint, P _ltrfor the low ebb load of electrical network, P _gminfor the conventional thermoelectricity of the whole network, water power consider that the minimum start of peak modulation capacity is exerted oneself, P _gfcthe situation of exerting oneself (mainly comprising the nuclear power, water power etc. that do not participate in peak regulation to exert oneself) is forced, P for the whole network _gpsthe peak regulation that can provide for hydroenergy storage station supports, P _dtrfor the power transmission power of direct current under base load (is considered the practical operation situation of current electrical network direct current, can be made $P_{\mathrm{Dtr}}=P_{\mathrm{new}}+\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{P}_{\mathrm{Di}}$ )。

5-2) check that to relatively rotate inertia index as follows,

$H_{\mathrm{dc}}=\frac{H_{\mathrm{actotal}}}{P_{\mathrm{dctotal}}}---\left(7\right)$

Wherein H _actotalrepresent total moment of inertia of AC system, P _dctotalrepresent total transmission capacity of all direct currents, namely work as H _dc>=C _hthink that relatively rotating inertia meets constraint, H _dc< C _hthink that relatively rotating inertia does not meet constraint, C _hbe the threshold value provided safely according to system frequency, generally get 2-3s.

Beneficial effect of the present invention is as follows: along with the development of electrical network scale, and the capacity of receiving end electrical network feed-in direct current is increasing, and direct current, while transmitting electric power for electrical network, solving shortage of electric power situation, also controls the new challenge brought to operation of power networks.Electrical production run unit more and more pays close attention to electrical network, and maximum that the ability of direct current can be received to have is much, electrical network receives how many DC operation comparatively economical, the present invention considers the multiple constraints in operation of power networks, solution for this problem provides a kind of method, contribute to fully realizing direct current and access the impact that electrical network is caused, make rational planning for, reduce direct current unchecked construction, improve operation of power networks economic benefit, reduce operation risk.

Accompanying drawing explanation

Fig. 1 is the flow chart of the inventive method;

Fig. 2 is the flow chart that in Fig. 1, step 2 selects direct current drop point.

Embodiment

With reference to the accompanying drawings the present invention is described in further detail.

What in Fig. 1, step 1 described is determine rack based on a certain, and note has wherein accessed M bar direct current, and the capacity of every bar direct current is respectively P _d,i(i=1,2 ..., M), form typical operation modes, the equal full capacity power transmission of M bar direct current wherein accessed, determines alternative direct current drop point set according to substation location condition, power balance etc., supposes total N number of alternative direct current drop point;

What in Fig. 1, step 2 described is according to the reciprocation degree between the capacity of short circuit of alternative direct current drop point each under typical way and each direct current, determines newly-increased direct current access drop point, and the initial capacity of new access direct current is designated as P _new(P _newrelevant with DC voltage level, ± 500kV is generally 3000MW, and ± 800kV is generally 8000MW, and ± 1000kV is generally 10000MW, and giving tacit consent to initial access capacity in this step is 8000MW).

What in Fig. 1, step 3 described is utilize in step 2 to have obtained direct current drop point, sets up new power system operating mode data, has accessed direct current transmission power and remained unchanged, newly-increased D.C. capacity P _new;

That in Fig. 1, step 4 describes is the effective short circuit ratio MESCR of many feed-ins calculating all M+1 bar direct currents _i(i=1,2 ..., M+1), if the effective short circuit ratio of many feed-ins of all direct currents is all greater than a certain threshold value R _ref(according to pertinent literature, R _refgenerally get 2-2.5), carry out step 5, otherwise carry out step 6;

What in Fig. 1, step 5 described is check electrical network low ebb peak modulation capacity, relatively rotates inertia index, N-1 transient stability, if all satisfy condition, makes M=M+1, returns step 1, otherwise carry out step 8;

That in Fig. 1, step 6 describes is the direct current transmission power P reducing new access _ad(P _adfor the direct current power adjustment step-length set according to acceptable error, as desirable 100MW), make P _new=P _new-P _ad, form new operational mode, calculate the effective short circuit ratio of many feed-ins of all direct currents, if the effective short circuit ratio of many feed-ins that still there is direct current is less than R _ref, return step 6, otherwise carry out step 7;

What in Fig. 1, step 7 described is check electrical network low ebb peak modulation capacity, relatively rotates inertia index, N-1 transient stability, if meet institute's Constrained, then carry out step 9, otherwise carry out step 8;

That in Fig. 1, step 8 describes is the direct current transmission power P reducing new access _ad, make P _new=P _new-P _ad, form new operational mode, check electrical network low ebb peak modulation capacity, relatively rotate inertia index, N-1 transient stability, if meet institute's Constrained, carry out step 9, otherwise return step 8;

What in Fig. 1, step 9 described is the direct current access capability calculating receiving end electrical network is $P_{\mathrm{inGrid}}=P_{\mathrm{new}}+\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{P}_{\mathrm{Di}}.$

In Fig. 1, step 2 is according to the reciprocation degree between the capacity of short circuit of alternative direct current drop point each under typical way and each direct current, and determine newly-increased direct current access drop point, its concrete grammar and step composition graphs 2 are described:

That in Fig. 2, step 2-1 describes is the effective short circuit ratio MSCR of many feed-ins calculating the M bar direct current accessed under typical way _i(i=1,2 ..., M), remember that the minimum direct current of the effective short circuit ratio of many feed-ins is numbered NUM;

That in Fig. 2, step 2-2 describes is the capacity of short circuit S calculating N number of alternative direct current drop point under typical way _{ac, j}(j=1,2 ..., N), remember that wherein capacity of short circuit maximum is S _acmax, capacity of short circuit minimum value is S _acmin, obtain the capacity of short circuit index S of a jth alternative direct current drop point _j,

$S_j=\frac{S_{\mathrm{ac},j}-S_{\mathrm{ac}\min }}{S_{\mathrm{ac}\max }-S_{\mathrm{ac}\min }},j=\mathrm{1,2},...,N---\left(1\right);$

What in Fig. 2, step 2-3 described is to jth alternative direct current drop point, calculate itself and accessed direct current drop point between equivalent impedance Z _{eq, mn}(m, n=1,2 ..., M, M+1; M+1 represents in the jth direct current that direct current drop point newly an accesses numbering), calculate new access direct current to all influence degree index A having accessed direct current according to equivalent impedance and direct current access capacity _j, new access direct current is to the influence degree index B of the weakest direct current _j, all direct currents that accessed are to the new influence degree index C accessing direct current _j, shown in it is calculated as follows,

$\left\{\begin{array}{c}{A}_{j,\mathrm{eq}}=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{\left|Z_{\mathrm{eq},i(M+1)}\right|P_{\mathrm{new}}}{\left|Z_{\mathrm{eq},\mathrm{ii}}\right|P_{d,i}}\\ B_{j,\mathrm{eq}}=\frac{\left|Z_{\mathrm{eq},\left(\mathrm{NUM}\right)(M+1)}\right|P_{\mathrm{new}}}{\left|Z_{\mathrm{eq},\left(\mathrm{NUM}\right)\left(\mathrm{NUM}\right)}\right|P_{d,i}}\\ C_{j,\mathrm{eq}}=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{\left|Z_{\mathrm{eq},(M+1)i}\right|P_{d,i}}{\left|Z_{\mathrm{eq},(M+1)(M+1)}\right|P_{\mathrm{new}}}\end{array}\right.---\left(2\right)$

To all N number of alternative direct current drop points, note

A _max＝max{A _1,eq,A _2,eq,...,A _N,eq,}，A _min＝min{A _1,eq,A _2,eq,...,A _N,eq,}

B _max＝max{B _1,eq,B _2,eq,...,B _N,eq,}，B _min＝min{B _1,eq,B _2,eq,...,B _N,eq,}

C _max＝max{C _1,eq,C _2,eq,...,C _N,eq,}，C _min＝min{C _1,eq,C _2,eq,...,C _N,eq,}

Carry out standardization to index can obtain,

$\left\{\begin{array}{c}{A}_j=\frac{A_{\max }-A_{j,\mathrm{eq}}}{A_{\max }-A_{j,\min }}\\ B_j=\frac{B_{\max }-B_{j,\mathrm{eq}}}{B_{\max }-B_{j,\min }}\\ C_j=\frac{C_{\max }-C_{j,\mathrm{eq}}}{C_{\max }-C_{j,\min }}\end{array}\right.---\left(3\right)$

What in Fig. 2, step 2-4 described is calculates and obtains when selecting jth alternative direct current drop point, new access direct current and accessed the level index that to influence each other between each direct current

$I_j=\frac{1}{3}(A_j+B_j+C_j)---\left(4\right)$

The direct current drop point selective goal that what in Fig. 2, step 2-5 described is under adopting linear weighted function summation approach to obtain a jth alternative direct current drop point,

LD _j＝λ ₁S _j+λ ₂I _j(5)

Wherein weight coefficient meets λ ₁+ λ ₂the constraint of=1, can adopt the method such as capacitive equipments, ranking method to obtain, and for the purpose of simple, can make λ ₁=λ ₂=0.5, the maximum drop point of selective goal value is as newly-increased direct current drop point.

Although the present invention with preferred embodiment openly as above, embodiment is not of the present invention for limiting.Without departing from the spirit and scope of the invention, any equivalence change done or retouching, belong to the protection range of the present invention equally.Therefore the content that protection scope of the present invention should define with the claim of the application is standard.

Claims (3)

1. consider receiving end electrical network direct current access capability computational methods for multiple constraint, it is characterized in that, comprise the steps:

Step one: determine rack based on a certain, note has wherein accessed M bar direct current, and the capacity of every bar direct current is respectively P _d,i, wherein, i=1,2 ..., M, form typical operation modes, the equal full capacity power transmission of M bar direct current wherein accessed, determines alternative direct current drop point set according to substation location condition, power balance etc., supposes total N number of alternative direct current drop point;

Step 2: according to the reciprocation degree between the capacity of short circuit of alternative direct current drop point each under typical way and each direct current, determines newly-increased direct current access drop point, and the initial capacity of new access direct current is designated as P _new.

Step 3: utilize in step 2 and obtained direct current drop point, sets up new power system operating mode data, and original direct current transmission power remains unchanged, newly-increased D.C. capacity P _new;

Step 4: the effective short circuit ratio MESCR of many feed-ins calculating all M+1 bar direct currents _i, wherein, i=1,2 ..., M+1, if the effective short circuit ratio of many feed-ins of all direct currents is all greater than a certain threshold value R _ref, carry out step 5, otherwise carry out step 6;

Step 5: check electrical network low ebb peak modulation capacity, relatively rotate inertia index, N-1 transient stability, if all satisfy condition, make M=M+1, return step one, otherwise carry out step 8;

Step 6: the direct current transmission power P reducing new access _ad, P _adfor the direct current power adjustment step-length set according to acceptable error, make P _new=P _new-P _ad, form new operational mode, calculate the effective short circuit ratio of many feed-ins of all direct currents, if the effective short circuit ratio of many feed-ins that still there is direct current is less than R _ref, return step 6, otherwise carry out step 7;

Step 7: check electrical network low ebb peak modulation capacity, relatively rotate inertia index, N-1 transient stability, if meet institute's Constrained, then carry out step 9, otherwise carry out step 8;

Step 8: the direct current transmission power P reducing new access _ad, make P _new=P _new-P _ad, form new operational mode, check electrical network low ebb peak modulation capacity, relatively rotate inertia index, N-1 transient stability, if meet institute's Constrained, carry out step 9, otherwise return step 8;

Step 9: the direct current access capability calculating receiving end electrical network is

2. a kind of receiving end electrical network direct current access capability computational methods considering multiple constraint according to claim 1, it is characterized in that, according to the reciprocation degree between the capacity of short circuit of alternative direct current drop point each under typical way and each direct current in described step 2, determine newly-increased direct current access drop point, its concrete grammar and step as follows:

Step 2-1: the effective short circuit ratio MESCR of many feed-ins of the M bar direct current accessed under calculating typical way _i, wherein, i=1,2 ..., M, remembers that the minimum direct current of the effective short circuit ratio of many feed-ins is numbered NUM;

Step 2-2: the capacity of short circuit S of N number of alternative direct current drop point under calculating typical way _{ac, j}, wherein, j=1,2 ..., N, remembers that wherein capacity of short circuit maximum is S _acmax, capacity of short circuit minimum value is S _acmin, obtain the capacity of short circuit index S of a jth alternative direct current drop point _j,

$S_j=\frac{S_{\mathrm{ac},j}-S_{\mathrm{ac}\min }}{S_{\mathrm{ac}\max }-S_{\mathrm{ac}\min }},(j=\mathrm{1,2},...,N)---\left(1\right);$

Step 2-3: to jth alternative direct current drop point, the equivalent impedance Z between the drop point calculating itself and original access direct current _{eq, mn}, wherein, m, n=1,2 ..., M, M+1, M+1 represent in the jth direct current that direct current drop point newly an accesses numbering, calculate new access direct current to all influence degree index A having accessed direct current according to equivalent impedance and direct current access capacity _j, new access direct current is to the influence degree index B of the weakest direct current _j, all direct currents that accessed are to the new influence degree index C accessing direct current _j, shown in it is calculated as follows,

$\left\{\begin{array}{c}{A}_{j,\mathrm{eq}}=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{\left|Z_{\mathrm{eq},i(M+1)}\right|P_{\mathrm{new}}}{\left|Z_{\mathrm{eq},\mathrm{ii}}\right|P_{d,i}}\\ B_{j,\mathrm{eq}}=\frac{\left|Z_{\mathrm{eq},\left(\mathrm{NUM}\right)(M+1)}\right|P_{\mathrm{new}}}{\left|Z_{\mathrm{eq},\left(\mathrm{NUM}\right)\left(\mathrm{NUM}\right)}\right|P_{d,i}}\\ C_{j,\mathrm{eq}}=\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{\left|Z_{\mathrm{eq},(M+1)i}\right|P_{d,i}}{\left|Z_{\mathrm{eq},(M+1)(M+1)}\right|P_{\mathrm{new}}}\end{array}\right.---\left(2\right)$

To all N number of alternative direct current drop points, note

A _max＝max{A _1,eq,A _2,eq,...,A _N,eq,}，A _min＝min{A _1,eq,A _2,eq,...,A _N,eq,}

B _max＝max{B _1,eq,B _2,eq,...,B _N,eq,}，B _min＝min{B _1,eq,B _2,eq,...,B _N,eq,}

C _max＝max{C _1,eq,C _2,eq,...,C _N,eq,}，C _min＝min{C _1,eq,C _2,eq,...,C _N,eq,}

Carry out standardization to index can obtain,

$\left\{\begin{array}{c}{A}_j=\frac{A_{\max }-A_{j,\mathrm{eq}}}{A_{\max }-A_{j,\min }}\\ B_j=\frac{B_{\max }-B_{j,\mathrm{eq}}}{B_{\max }-B_{j,\min }}\\ C_j=\frac{C_{\max }-C_{j,\mathrm{eq}}}{C_{\max }-C_{j,\min }}\end{array}\right.---\left(3\right)$

Step 2-4: calculate and obtain when selecting jth alternative direct current drop point, influence each other between new access direct current and each direct current of original access level index

$I_j=\frac{1}{3}(A_j+B_j+C_j)---\left(4\right)$

Step 2-5: the direct current drop point selective goal under adopting linear weighted function summation approach to obtain a jth alternative direct current drop point,

LD _j＝λ ₁S _j+λ ₂I _j(5)

Wherein weight coefficient meets λ ₁+ λ ₂the constraint of=1, can adopt the method such as capacitive equipments, ranking method to obtain, and the maximum drop point of selective goal value is as newly-increased direct current drop point.

3. a kind of receiving end electrical network direct current access capability computational methods considering multiple constraint according to claim 1, is characterized in that, described step 5 lieutenant colonel nuclear power net low ebb peak modulation capacity, relatively rotate inertia index, and its concrete grammar is as follows:

Step 5-1: check electrical network low ebb peak modulation capacity and adopt following index,

η _tr＝P _Ltr-P _Gmin-P _Gfc+P _Gps-P _Dtr-P _Grn(6)

Wherein η _trfor electrical network low ebb peak regulation nargin, if η _tr>=0 illustrates that electrical network low ebb peak modulation capacity meets constraint, η _tr< 0 illustrates that electrical network low ebb peak modulation capacity does not meet constraint, P _ltrfor the low ebb load of electrical network, P _gminfor the conventional thermoelectricity of the whole network, water power consider that the minimum start of peak modulation capacity is exerted oneself, P _gfcthe situation of exerting oneself is forced, P for the whole network _gpsthe peak regulation that can provide for hydroenergy storage station supports, P _dtrfor the power transmission power of direct current under base load;

Step 5-2: it is as follows that check relatively rotates inertia index,

$H_{\mathrm{dc}}=\frac{H_{\mathrm{actotal}}}{P_{\mathrm{dctotal}}}---\left(7\right)$

Wherein H _actotalrepresent total moment of inertia of AC system, P _dctotalrepresent total transmission capacity of all direct currents, namely work as H _dc>=C _hthink that relatively rotating inertia meets constraint, H _dc< C _hthink that relatively rotating inertia does not meet constraint, C _hit is the threshold value provided safely according to system frequency.