CN102214922B - Evaluation system of power network planning scheme - Google Patents

Abstract

The invention discloses an evaluation system of a power network planning scheme, comprising an adequacy evaluation module, a safety evaluation module, a tidal current distribution rationality evaluation module and a short-circuit current rationality evaluation module, wherein the adequacy evaluation module evaluates the capacity of an electric power system to meet electric power and electric energy of a user under the static condition; the safety evaluation module evaluates the capacity of the electric power system to endure sudden disturbance and provide the electric power and the electric energy to the user continuously under a dynamic condition; the tidal current distribution rationality evaluation module estimates size distribution of line loads and load distribution indexes of the whole transmission network; and the short-circuit current rationality evaluation module detects the maximal short-circuit current, thus short-circuit capacity of each station in the system is kept in the range of the rated cutting-off capacity of equipment. The evaluation system provides a basis for selecting the most reasonable planning scheme.

Description

A kind of evaluating system of power network planning scheme

Technical field

The present invention relates to a kind of evaluating system of power network planning scheme.

Background technology

In the world, a large-scale market-oriented reform is being carried out in electric power system, whether the economy of electric power transmission network is reasonable, and whether fail safe meets the demands, and whether transmission capacity, grid structure reach the most excellent vital interests that are all related to different main market players.Along with progressively going deep into of China's interconnected network scale expanding day, " separate the factory and network, surf the Net at a competitive price " reform, the uncertain factor of operation of power networks increases, and the Transmission Expansion Planning in Electric work of China is also faced with huge challenge.

The basic demand of Electric Power Network Planning guarantees that electric energy safe effectively delivers to user exactly, Transmission Expansion Planning in Electric not only will be considered the reliability of Transmission Expansion Planning in Electric, also to consider the reasonability of planning, therefore how determining the satisfaction degree of each programme of quantitative analysis to technical requirement, is current urgent problem.

Summary of the invention

For making up the deficiencies in the prior art, the invention provides a kind of evaluating system of power network planning scheme.

For achieving the above object, the present invention adopts following technical scheme:

An evaluating system for power network planning scheme, it comprises adequacy evaluation module, security assessment module, trend distribution rationality evaluation module and short circuit current reasonable evaluation module; Described adequacy evaluation module estimation is under static conditions, and electric power system meets the ability of user to electric power and electric flux; Described security assessment module is evaluated at electric power system under dynamic condition and withstands Sudden Disturbance, and the ability of electric power and electric flux is provided to user incessantly; Described trend distribution rationality evaluation module utilizes the size distribution of line load and the load Distribution index of whole electric power transmission network to assess; Described short circuit current reasonable evaluation module is carried out the check of maximum short circuit current so that in system the capacity of short circuit of each plant stand all within the scope of the specified connecting-disconnecting function of equipment;

Wherein: adequacy evaluation module estimation relates to trend calculating, accident analysis and eliminates and transships, generates electricity to reschedule, load and cut down and handover operation; Described security assessment module is utilized the transient stability of transient stability fault scanning program to each programme exhaustive examination network to be evaluated, after exhaustive scanning, can show that the number of times of Transient Instability appears in system under given failure collection, and adopt fuzzy evaluation set to be quantified as evaluation index.

Described adequacy evaluation module estimation method is as follows:

Step1: first obtain Future Power System rack data and generating and the prediction data of loading, and the Technical Economic Data of generating equipment;

Step2: in power transmission network, transmission line adopts forced outage model, and adopt non-sequential Monte Carlo simulation select POWER SYSTEM STATE and calculate their probability;

Step3: after POWER SYSTEM STATE is determined, select certain load level of load condition;

Step4: carry out Monte Carlo sampling, by sampled analog network state, and judge whether this network state has circuit to disconnect, as circuit proceeds to step7 continuation execution without disconnecting;

Step5: disconnect and judge whether circuit is still communicated with if any circuit, proceeding in this way step6 carries out, otherwise network is divided into isolated node and major part network, calculate major part network trend and isolated node and lack load, and judge that whether major part network trend transships, and proceeds to step8 in this way;

Step6: revise admittance matrix;

Step7: calculate trend and whether transship;

Step8: have a tidal wave of to flow through to carry and call minimum tangential load function, and overload counting is added to one, record load;

Step9: judge whether Monte Carlo frequency in sampling reaches maximum, proceed in this way step10, continue to carry out otherwise proceed to step4;

Step10: calculate that load under the load level that step8 records is cut down probability and expectation lacks amount of power supply;

Step11: judge whether that load under all load levels cuts down probability and expectation and lack amount of power supply and all calculate completely, as do not calculate the complete step3 that proceeds to and proceed; Otherwise the load that calculates electric power system cuts down probability and expectation lacks amount of power supply.

The variance of each line load rate of utilizing described trend distribution rationality evaluation module reflects in the fluctuation situation of all line load rates, maximum load rate in peak load situation lower network can reflect the ability to bear of network under peak load, and the formula of each corresponding index is defined as:

Maximum load rate=max (l ₁, l ₂... l _n)

Wherein: n is the number of lines, l _ibe i bar line load rate,

mean value for all line load rates.

Described short circuit current reasonable evaluation module utilizes the mean value of each bus three-phase shortcircuit electric current allowance to characterize short circuit current reasonability index, and its expression formula is:

Wherein: m represents total number of node.

Described POWER SYSTEM STATE deterministic process is as follows: the reliability of electric power system determines by electricity generation system, transmission system and load three parts are common, because hypothesis electricity generation system 100% is reliable, so system mode depends on transmission system state and load condition;

(a) deterministic process of transmission system state: transmission line operational failure and the simulation of operation binary states stochastic variable, every one of used for transmission line is simulated at [0,1] interval uniform random number; Suppose that every line failure is separate, makes S _i, F _irepresent respectively state and the probability of malfunction of circuit i, R _ifor [0,1] interval random number that circuit i is generated, circuit i state is:

$S_i=\left\{\begin{array}{cc}0,& 0\&le;R_i\&le;F_i\\ 1,& F_i<R_i\&le;1\end{array}\right.$

S wherein _i=0 representing fault state, S _i=1 represents running status, and when system is comprised of N bar circuit, system transmission system state representation is:

S＝(S ₁，S ₂，...S _N)

(b) deterministic process of load treatment system state: very many owing to affecting the factor of payload, and some is to be difficult to prediction, so be difficult to the exact value of prediction load definitely, use Monte Carlo Analogue Method can simulate the change at random characteristic of load, make evaluation result more objective; The randomness of general load variations is simulated with normal distribution random number, establishes node j load for L _j, and node j load obedience average is μ _j, standard deviation is σ _jnormal distribution:

$L_j~N({\mathrm{\&mu;}}_j,{\mathrm{\&sigma;}}_j^2)$

When system is comprised of M load bus, the load condition of system is:

L＝(L ₁，L ₂，...L _M)

Comprehensive transmission system and system loading two parts, the state of system can be expressed as:

Sys＝(S，L)。

Beneficial effect: native system utilizes adequacy evaluation module under static conditions, has assessed electric power system and has met the ability of user to electric power and electric flux; Utilize security assessment module to assess electric power system under dynamic condition and withstand Sudden Disturbance, and the ability of electric power and electric flux is provided to user incessantly; Utilize trend distribution rationality evaluation module to assess the load Distribution index of the size distribution of line load and whole electric power transmission network; Utilize short circuit current reasonable evaluation module to carry out the check of maximum short circuit current so that in system the capacity of short circuit of each plant stand all within the scope of the specified connecting-disconnecting function of equipment.The present invention provides foundation for selecting the most rational programme.

Accompanying drawing explanation

Fig. 1 is transmission line two states model;

Fig. 2 is adequacy evaluation flow chart;

Fig. 3 is fuzzy evaluation set quantification figure;

Fig. 4 is garver-6 system original net shelf structure schematic diagram;

Fig. 5 is the grid structure schematic diagram of the feasible programme 1 of garver-6 system;

Fig. 6 is the grid structure schematic diagram of the feasible programme 2 of garver-6 system;

Fig. 7 is the grid structure schematic diagram of the feasible programme 3 of garver-6 system;

Fig. 8 is the grid structure schematic diagram of the feasible programme 4 of garver-6 system;

Fig. 9 is the grid structure schematic diagram of the feasible programme 5 of garver-6 system.

Embodiment

Below in conjunction with drawings and Examples, the invention will be further described:

The basic demand of Electric Power Network Planning guarantees that electric energy safe effectively delivers to user exactly, so technical indicator is an essential and most important aspect in overall merit.Technical indicator comprises adequacy indexes, safety indexes, trend distribution rationality index and short circuit current reasonability index.Wherein, two indexs of abundant intensity and fail safe are characterizing the reliability of electric power system.

(1) abundant intensity

Abundant intensity refers to be considered the planned outage of element and is reasonably expecting in unplanned stoppage in transit situation, and electric power system maintains the ability of the total electricity needs of continuous supply user and total electric flux.Abundant intensity claims again static reliability, and namely, under static conditions, electric power system meets the ability of user to electric power and electric flux.

The adequacy evaluation of transmission system relates to trend calculating, accident analysis and reschedules, loads and cut down and the corrective measure such as handover operation such as eliminating overload, generating.Generally include the content of following four aspects:

● determine element outage model

Using power transmission network as the main target of paying close attention to, therefore to suppose that other system 100% is reliable, thereby only carry out transmission system adequacy evaluation, transmission system adequacy evaluation is only considered line out of service.

The stoppage in transit pattern of transmission line has the multiple stoppage in transit patterns such as forced outage, planned outage, half forced outage, partial failure.Wherein forced outage can be divided into again can repairing to force and lost efficacy and unrepairable forces inefficacy.The random generation of forced outage and most of forced outage are recoverable.For simplifying, calculate, in Transmission System Reliability Evaluations, conventionally adopt forced outage model, and suppose that transmission line is two states model, as shown in Figure 1:

● selective system state also calculates their probability

System mode can adopt analytic method or Monte Carlo Analogue Method to select.Analytic method adopts Fault enumeration to carry out condition selecting, and generally, the selection of the system failure is to select one by one by certain logic, and when system is comprised of N two state elements, the status number of system is 2 so ⁿtherefore the number of system mode is that increase with system element number is exponential increase, so, for the system that includes a large amount of elements, enumerate all system modes is unpractical on calculating, and a kind of common way is to terminate on certain given level enumerating.Monte Carlo Analogue Method utilizes arbitrary sampling method to carry out condition selecting, according to the difference of random sampling principle, can be divided into again sequential Monte Carlo simulation and non-sequential Monte Carlo simulation, the method amount of calculation does not increase with system scale, has more superiority when calculating large scale system.

Analytic method physical concept is clear, model accuracy is high but be not easy to process large scale system, and Monte Carlo method belongs to statistical test method, simple, intuitive, is easy to by engineers and technicians, grasped and understand, and easily process multiple faults situation, be convenient to process the change at random characteristic of load, China's network capacity constantly increases in recent years simultaneously, and network size is increasing, therefore, herein, adopt non-sequential Monte Carlo simulation selective system state.

The reliability of system determines by electricity generation system, transmission system and load three parts are common, because hypothesis electricity generation system 100% is reliable, so system mode depends on transmission system state and load condition.

(a) transmission line operational failure and the simulation of operation binary states stochastic variable, every one of used for transmission line is simulated at [0,1] interval uniform random number.Suppose that every line failure is separate, makes S _i, F _irepresent respectively state and the probability of malfunction of circuit i, R _ifor [0,1] interval random number that circuit i is generated, circuit i state is:

$S_i=\left\{\begin{array}{cc}0,& 0\&le;R_i\&le;F_i\\ 1,& F_i<R_i\&le;1\end{array}\right.---(1-1)$

S wherein _i=0 representing fault state, S _i=1 represents running status, and when system is comprised of N bar circuit, system transmission system state representation is:

S＝(S ₁，S ₂，...S _N) (1-2)

(b) load in reliability assessment is processed.Owing to affecting, the factor of payload is very many, and some is to be difficult to prediction, so be difficult to the exact value of prediction load definitely, uses Monte Carlo Analogue Method can simulate the change at random characteristic of load, makes evaluation result more objective.The randomness of general load variations is simulated with normal distribution random number, establishes node j load for L _j, and node j load obedience average is μ _j, standard deviation is σ _jnormal distribution:

$L_j~N({\mathrm{\&mu;}}_j,{\mathrm{\&sigma;}}_j^2)---(1-3)$

When system is comprised of M load bus, the load condition of system is:

L＝(L ₁，L ₂，...L _M) (1-4)

Comprehensive transmission system and system loading two parts, the state of system can be expressed as:

Sys＝(S，L) (1-5)

● forecast accident analysis and corrective action

After system mode is determined, just need to system carry out accident analysis with recognition system whether in malfunction.The object of transmission system forecast accident analysis is Line Flow and the busbar voltage of calculating after one or more line out of service, to identify, whether causes that circuit overload, voltage out-of-limit, bus isolate or system is separated into the problems such as isolated island.When line out of service causes system problem, just need to eliminate system restriction by corrective action and disobey limit, the simultaneously the least possible load of avoiding is cut down.

The method of forecast accident analysis mainly contains AC power flow method and DC power flow algorithm.Owing to need to the system mode of magnanimity being carried out to accident analysis, in order to reduce amount of calculation, often adopt the DC power flow analytic approach to carry out accident analysis, in DC power flow algorithm, omitted all relevant to reactive power amount, for the assessment of programme, this is an acceptable Rational Simplification.

When line fault causes system problem, generally by generating, reschedule measure and proofread and correct to eliminate system problem, the reduction that simultaneously makes to load is minimum, is expressed as the minimum load shedding model based on DC power flow, and its mathematic(al) representation is:

$\min \underset{i\&Element;\mathrm{ND}}{\mathrm{\&Sigma;}}{C}_i$

S.t.

P(Sys)＝A(Sys)(PG-PD+C)

$\underset{i\&Element;\mathrm{NG}}{\mathrm{\&Sigma;}}{\mathrm{PG}}_i+\underset{i\&Element;\mathrm{ND}}{\mathrm{\&Sigma;}}{C}_i=\underset{i\&Element;\mathrm{ND}}{\mathrm{\&Sigma;}}{\mathrm{PD}}_i---(1-6)$

${\mathrm{PG}}_i^{\min }\&le;{\mathrm{PG}}_i\&le;{\mathrm{PG}}_i^{\max }(i\&Element;\mathrm{NG})$

0≤C _i≤PD _i(i∈ND)

$\left|P_k\left(\mathrm{Sys}\right)\right|\&le;P_k^{\max }(k\&Element;L)$

● computed reliability index

If minimum load reduction is not 0 under state Sys, this state is thrashing state.When the quantity of random sampling is enough large, the sampling frequency of state Sys can be used as its probability without inclined to one side estimation.Suppose the number of times that m (Sys) occurs in random sampling for state Sys, M is random sampling numbers, and the probability of state Sys is:

$P\left(\mathrm{Sys}\right)=\frac{m\left(\mathrm{Sys}\right)}{M}---(1-7)$

The index system of adequacy evaluation, basic index comprises probability, frequency, duration and desired value 4 classes, and the complexity of calculating according to index is chosen the index that probability and desired value index are evaluated as programme abundant intensity, and computing formula is:

(a) load is cut down probability (probability of load curtailments)

$\mathrm{PLC}=\underset{i=1}{\overset{\mathrm{NL}}{\mathrm{\&Sigma;}}}\left(\underset{\mathrm{Sys}\&Element;F_i}{\mathrm{\&Sigma;}}P\left(\mathrm{Sys}\right)\right)\frac{T_i}{T}---(1-8)$

NL is load condition number, F _ifor the set of thrashing state under load condition i, T _ibe the time span of load level i, T is (h) during total time of load curve.

(b) expectation lacks amount of power supply EENS (during MWh/) (expected energy not supplied)

$\mathrm{EENS}=\underset{i=1}{\overset{\mathrm{NL}}{\mathrm{\&Sigma;}}}(\underset{s\&Element;F_i}{\mathrm{\&Sigma;}}P\left(\mathrm{Sys}\right)*C\left(\mathrm{Sys}\right))*T_i---(1-9)$

Wherein C (Sys) is the load reduction of system under state Sys.

The content of comprehensive above each side, the calculation flow chart of transmission system abundant intensity as shown in Figure 2:

(2) fail safe

Fail safe refers to that electric power system bears the disturbance of unexpected generation, such as suddenly-applied short circuit or the short circuit of not expecting or lose the ability of the phenomenons such as system element.Fail safe also claims dynamic reliability, and under dynamic condition, electric power system withstands Sudden Disturbance, and the ability of electric power and electric flux is provided to user incessantly.

The object of safety evaluation is to estimate the ability to bear of electric power system to catastrophic failure, the method of safety evaluation has certainty assessment and probabilistic assessment, various countries, at planning and design of power system and in service, prevailingly all adopt deterministic computational methods in the world at present.The evaluation of certainty power system stability refers under the condition of given NETWORK STRUCTURE PRESERVING POWER SYSTEM, parameter, disturbance type and scene, uses deterministic Mathematical Modeling, evaluates electric power system and whether keeps stable.Certainty transient stability calculates following supposition and regulation:

1. supposition short trouble is metallicity;

2. do not consider the effect of DC component in short circuit current and suppose that generator unit stator resistance is zero;

3. press the equivalence model of selecting generating set to provisioning request, and think that rotary speed of generator group is near rated value;

4. given relaying protection operate time, the time of reclosing and automatic safety device can be determined given or as calculated.

Transient stability computing module in Based on Power System Analysis Software Package PSASP can be good at simulating various faults perturbation scheme and stabilizing measures, therefore utilizes PSASP synthesizer to carry out transient stability calculating herein.But because amount of calculation is huge, therefore utilize the transient stability of Visual FoxPro language compilation transient stability fault scanning program to each programme exhaustive examination network to be evaluated.

After exhaustive scanning, can show that the number of times of Transient Instability appears in system under given failure collection, and adopt fuzzy evaluation set to be quantified as evaluation index, the assignment of fuzzy evaluation set is shown in 3:

(3) trend distribution rationality

Reasonably trend distribution is the basis of grid health economical operation.Trend distribution rationality can utilize the size distribution of line load and the load Distribution index of whole electric power transmission network to reflect.If the heavy-loaded line way of network is too much, the investment shortcoming of this network is described, need to strengthen investment construction to alleviate circuit operation level, strengthen light power handling capabilities, meet the needs of load growth utmost point scheduling in breakdown state, the residue transmission line capability of system is not enough; And if light-loaded circuit is too much, explanation residue transmission line capability is large, and network scheduling ability is strong, but also explanation investment is too leading accordingly, causes the wasting of resources, and the two is not that we wish to see.A while rational grid structure, should not that some line load utilances are very low, and other circuit is approaching, meet, there is " network bottleneck " in explanation in this case, therefore utilize the variance of each line load rate to reflect in the fluctuation situation of all line load rates, called after load balancing degrees index.The maximum load rate of this external peak load situation lower network can reflect the ability to bear of network under peak load.The formula of each corresponding index is defined as:

Maximum load rate=max (l ₁, l ₂... l _n) (1-13)

Wherein n is the number of lines, l _ibe i bar line load rate,

mean value for all line load rates.

(4) short circuit current reasonability

Along with the expansion of electrical network scale and the growth of installed capacity, the short circuit current level of system constantly increases, the increase of short circuit current will bring hidden danger to the safe operation of equipment, must adopt replacing operational mode or the more measure of large capcity breaker of changing to reduce its impact.Therefore, power network planning scheme assessment need to be carried out the check of maximum short circuit current so that in system the capacity of short circuit of each plant stand all within the scope of the specified connecting-disconnecting function of equipment.Adopt the mean value of each bus three-phase shortcircuit electric current allowance to characterize short circuit current reasonability index herein, its expression formula is:

Embodiment:

Adopt garver-6 system herein, its original net shelf structure as shown in Figure 4.The grid structure of 5 feasible programmes of this system is respectively as shown in Fig. 5～9.

Each node load adopts random normal distribution, and each node load and node generating maximum output data are as shown in table 1:

Table 1garver-6 system generating and load data

Node number	Load average (MW)	Standard deviation	Node maximum generation exert oneself (MW)
				1	84	8	110

2	253	25	0
				3	40	4	220
4	170	17	0
				5	253	25	0
6	0	0	735

It is 0.0001 that abundant intensity is got all line outage probability in calculating, utilize the stochastic behaviour of Monte Carlo Analogue Method simulation load, the load curve duration is 8760h, and adopt the minimum load shedding model based on DC power flow to carry out accident analysis, according to the flow chart of adequacy evaluation shown in Fig. 2, write matlab calculation procedure, calculate each scheme load and cut down probability and expect to lack power supply value year.

In order to carry out fail safe scanning, for garver-6 system has been supplemented system generator parameter, and in synthesizer PSASP, set up each programme basic database, the larger load of the system of getting 900MW tests, and each node generated output and load value are in Table 2.

The generating of table 2 node and load value

Node number	Generated output (MW)	Load value (MW)
			1	110	95
2	0	285
			3	220	45
4	0	190
			5	0	285
6	570	0

The fault type that carries out considering when transient stability scanning is calculated is in Table 3, and transient stability measure adopts the machine measure of cutting.After considering stabilizing measures, exhaustive scans each scheme, and Transient Instability situation does not all appear in each scheme, and therefore, it is 1 that each scheme comment value is all composed.

Table 3 transient stability calculates the fault type of considering

According to the PSASP database of setting up, utilize the trend in synthesizer to calculate and short circuit calculation function, can draw meritorious trend value and each busbar short-circuit current value of each circuit, respectively as shown in table 4 and table 5, in this example, set load factor >=0.9 for heavy-haul line, load factor≤0.1 is light-loaded circuit, according to formula (1-10)～(1-14), calculates trend distribute each index and short circuit current reasonability.

Each branch road of each scheme of table 4 trend value of gaining merit

Each busbar short-circuit current value of each scheme of table 5

Bus name	Scheme 1 (kA)	Scheme 2 (kA)	Scheme 3 (kA)	Scheme 4 (kA)	Scheme 5 (kA)
						b1	9.9946	9.9952	9.9976	9.9971	10.0057
b2	10.068	10.0658	10.0634	10.0635	10.0637
						b3	10.0156	10.0207	10.024	10.0364	10.0191
b4	10.0229	10.0233	10.0228	10.0232	10.0397
						b5	9.9969	10.0154	10.0139	10.0118	10.0061
b6	10.0867	10.0877	10.0882	10.089	10.0864

As shown in table 6 according to calculating above each evaluation index value:

Each programme desired value of table 6garver-6 example

Claims (5)

1. an evaluating system for power network planning scheme, is characterized in that, it comprises adequacy evaluation module, security assessment module, trend distribution rationality evaluation module and short circuit current reasonable evaluation module; Described adequacy evaluation module estimation is under static conditions, and electric power system meets the ability of user to electric power and electric flux; Described security assessment module is evaluated at electric power system under dynamic condition and withstands Sudden Disturbance, and the ability of electric power and electric flux is provided to user incessantly; Described trend distribution rationality evaluation module utilizes the size distribution of line load and the load Distribution index of whole electric power transmission network to assess; Described short circuit current reasonable evaluation module is carried out the check of maximum short circuit current so that in system the capacity of short circuit of each plant stand all within the scope of the specified connecting-disconnecting function of equipment;

Wherein: adequacy evaluation module estimation relates to trend calculating, accident analysis and eliminates and transships, generates electricity to reschedule, load and cut down and handover operation; Described security assessment module is utilized the transient stability of transient stability fault scanning program to each programme exhaustive examination network to be evaluated, after exhaustive scanning, can show that the number of times of Transient Instability appears in system under given failure collection, and adopt fuzzy evaluation set to be quantified as evaluation index;

The assignment of described fuzzy evaluation set is [1,0.75,0.5,0.25,10 ^-5].

2. the evaluating system of a kind of power network planning scheme as claimed in claim 1, is characterized in that, described adequacy evaluation module estimation method is as follows:

Step1: first obtain Future Power System rack data and generating and the prediction data of loading, and the Technical Economic Data of generating equipment;

Step2: in power transmission network, transmission line adopts forced outage model, and adopt non-sequential Monte Carlo simulation select POWER SYSTEM STATE and calculate their probability;

Step3: after POWER SYSTEM STATE is determined, select certain load level of load condition;

Step4: carry out Monte Carlo sampling, by sampled analog network state, and judge whether this network state has circuit to disconnect, as circuit proceeds to step7 continuation execution without disconnecting;

Step5: disconnect and judge whether circuit is still communicated with if any circuit, proceeding in this way step6 carries out, otherwise network is divided into isolated node and major part network, calculate major part network trend and isolated node and lack load, and judge that whether most of network trend transships, and proceeds to step8 in this way;

Step6: revise admittance matrix;

Step7: calculate trend and whether transship;

Step8: have a tidal wave of to flow through to carry and call minimum tangential load function, and overload counting is added to one, record load;

Step9: judge whether Monte Carlo frequency in sampling reaches maximum, proceed in this way step10, continue to carry out otherwise proceed to step4;

Step10: calculate that load under the load level that step8 records is cut down probability and expectation lacks amount of power supply;

Step11: judge whether that load under all load levels cuts down probability and expectation and lack amount of power supply and all calculate completely, as do not calculate the complete step3 that proceeds to and proceed; Otherwise the load that calculates electric power system cuts down probability and expectation lacks amount of power supply.

3. the evaluating system of a kind of power network planning scheme as claimed in claim 1, it is characterized in that, the variance of each line load rate of utilizing described trend distribution rationality evaluation module reflects in the fluctuation situation of all line load rates, maximum load rate in peak load situation lower network can reflect the ability to bear of network under peak load, and the formula of each corresponding index is defined as:

Maximum load rate=max (l ₁, l ₂... l _n)

Wherein: n is the number of lines, l _ibe i bar line load rate,

mean value for all line load rates.

4. the evaluating system of a kind of power network planning scheme as claimed in claim 1, is characterized in that, described short circuit current reasonable evaluation module utilizes the mean value of each bus three-phase shortcircuit electric current allowance to characterize short circuit current reasonability index, and its expression formula is:

Wherein: m represents total number of node.

5. the evaluating system of a kind of power network planning scheme as claimed in claim 2, it is characterized in that, described POWER SYSTEM STATE deterministic process is as follows: the reliability of electric power system determines by electricity generation system, transmission system and load three parts are common, because hypothesis electricity generation system 100% is reliable, so system mode depends on transmission system state and load condition;

(a) deterministic process of transmission system state: transmission line operational failure and the simulation of operation binary states stochastic variable, every one of used for transmission line is simulated at [0,1] interval uniform random number; Suppose that every line failure is separate, S _i, F _irepresent respectively state and the probability of malfunction of circuit i, R _ifor [0,1] interval random number that circuit i is generated, circuit i state is:

$S_i=\left\{\begin{array}{c}\mathrm{0,0}\&le;R_i\&le;F_i\\ 1,F_i<R_i\&le;1\end{array}\right.$

S wherein _i=0 representing fault state, S _i=1 represents running status, and when system is comprised of N bar circuit, system transmission system state representation is:

S=(S ₁,S ₂,...S _N)

(b) deterministic process of load treatment system state: very many owing to affecting the factor of payload, and some is to be difficult to prediction, so be difficult to the exact value of prediction load definitely, use Monte Carlo Analogue Method can simulate the change at random characteristic of load, make evaluation result more objective; The randomness of general load variations is simulated with normal distribution random number, establishes node j load for L _i, and node j load obedience average is u _j, standard deviation is δ _jnormal distribution:

$L_j~N({\mathrm{\&mu;}}_j,{\mathrm{\&sigma;}}_j^2)$

When system is comprised of M load bus, the load condition of system is:

L=(L ₁,L ₂,...L _M)

Comprehensive transmission system and system loading two parts, the state of system can be expressed as:

Sys＝(S,L)。

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