CN109193634A - Island operation of power networks optimization method and system based on multiterminal flexible direct current - Google Patents
Island operation of power networks optimization method and system based on multiterminal flexible direct current Download PDFInfo
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- CN109193634A CN109193634A CN201811139182.5A CN201811139182A CN109193634A CN 109193634 A CN109193634 A CN 109193634A CN 201811139182 A CN201811139182 A CN 201811139182A CN 109193634 A CN109193634 A CN 109193634A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/008—Circuit arrangements for ac mains or ac distribution networks involving trading of energy or energy transmission rights
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
- H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/18—Arrangements for adjusting, eliminating or compensating reactive power in networks
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
- H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/30—Reactive power compensation
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Abstract
The invention discloses island operation of power networks optimization methods and system based on multiterminal flexible direct current, comprising: establishes the ac grid voltage Optimized model based on multiterminal flexible direct current, the objective function of the Optimized model comprehensively considers Web-based exercise and Reactive-power control amount cost；The active power of inverter injection AC system and reactive power are considered as control variable, meanwhile, control variable should also include the switching group number of compensating electric capacity, and state variable is then generator output and each node voltage of system；The coding mode of traditional genetic algorithm, mutation operator and constraint conditional processing method are improved, propose a kind of Revised genetic algorithum solving optimization model, and simulation analysis, the benefit of Integrated Evaluation Model are carried out to solving result.The work of this paper shows that the model has certain meaning to the wattles power economic equivalent containing soft lineal system, has a good application prospect.
Description
Technical field
The present invention relates to operation of power networks technical fields, excellent more particularly to the island operation of power networks based on multiterminal flexible direct current
Change method and system.
Background technique
Compared with traditional continental Grid, island power grid often exists more difficult in terms of operation.Such as grid structure phase
To weakness, it is limited to adjust nargin；Idle charge power on sea cable route is usually larger, influences the voltage level in system；It is negative
Lotus peak valley is obvious, and the method for operation is changeable etc..Therefore, often difficulty is bigger for the scheduling and operation of island power grid, usually along with more
Frequent reactive power compensator switching, causes additional economic loss.Therefore, operation of power networks optimization problem in island is worth deeply grinding
Study carefully.
Various researchs have been carried out to the optimization problem of traditional power grid in many researchers.Some documents are calculated by heredity
Method, particle swarm optimization algorithm and tabu search algorithm etc., by adjusting power supply (synchronous generator and the idle benefit in electric system
Repay equipment) power output, load tap changer position, line parameter circuit value etc. carry out the method for operation of optimization system, carry out optimal load flow calculating.
The thinking of part document application Multi-objective optimal power flow takes into account power generation expense minimum or loss minimization, static electric voltage stability most
Good, transmission capacity available maximum etc. requires, and has combined the economy and safety of Operation of Electric Systems.
In terms of the voltage optimization that flexible DC transmission technology is introduced to ac and dc systems, domestic and foreign scholars are also opened
The research of opening up property proposes different model and algorithm.Such as based on soft straight steady-state model and control mode, using interior point method pair
Ac and dc systems carry out optimal load flow calculating；Based on differential evolution algorithm and primal dual interior point method, propose that unified mixed iteration is calculated
Method is to solve the optimal load flows of ac and dc systems；With the minimum target of the via net loss of entire ac and dc systems, propose to contain multiterminal
The ac and dc systems optimal load flow algorithm of flexible DC transmission, and analyze in different VSC control strategies and containing wind power plant
Algorithm performance.Separately there is the characteristics of document is for flexible direct current, mentions while going out so that active power loss is minimum, voltage level is best, is
The static voltage stability degree of system is maximum and power supply capacity maximum is as optimization aim, constructs the multiobjective optimization of ac and dc systems
Tide model.
However, current research method is confined to theoretically carry out voltage to the ac and dc systems containing flexible direct current mostly
Optimization, about flexible HVDC transmission system to the positive influence of alternating current-direct current economic power system, especially in Practical Project level
Influence to island power grid, it is also necessary to further research.
Summary of the invention
In order to solve the deficiencies in the prior art, the present invention provides the island operation of power networks optimizations based on multiterminal flexible direct current
Method actively adjusts active and idle ability this process employs VSC, and consider compared with traditional power grid optimization method
The pressure of engineering island electric network reactive compensation frequent switching in practice, when system operation mode is switched Reactive-power control it is economical at
This introducing optimization aim, and derivation algorithm is improved to improve efficiency.
To achieve the goals above, the application uses following technical scheme:
Island operation of power networks optimization method based on multiterminal flexible direct current, comprising:
The ac grid voltage Optimized model based on multiterminal flexible direct current is established, the objective function of the Optimized model is except tradition
Transmission loss index outside, further include economic cost needed for Reactive-power control；
The active power of inverter injection AC system and reactive power are considered as control variable, actively adjusted using VSC
Active ability optimizes distribution of the active power between parallel ac and dc circuit, to indirectly control idle flowing；By VSC
The reactive compensation means that idle ability is actively adjusted as continuously adjustable put into operation, optimize capacitor group switching number,
Meanwhile controlling variable should also include the switching group number of compensating electric capacity, state variable is then generator output and each node electricity of system
Pressure；
Using Revised genetic algorithum to solve Optimized model, it is contemplated that compensating electric capacity is discrete magnitude, and soft straight active
Idle is continuous quantity, in solution by the way of integer and real number hybrid coding；Penalty term is introduced into objective function, with processing
Inequality constraints condition；It is gradually reduced using with evolutionary generation increase, while being no more than the change of preset minimum aberration rate
Different algorithm.
In above-mentioned technical proposal, the ac grid voltage Optimized model based on multiterminal flexible direct current, it is contemplated that system operation
When mode switches, reactive-load compensation equipment switching operation needs to pay certain economic cost, and the objective function of the Optimized model removes
Outside traditional transmission loss index, economic cost needed for further comprising Reactive-power control.
VSC is actively adjusted to idle ability to put into operation as the reactive compensation means of continuously adjustable, optimizes capacitor
Device group switching frequency improves voltage level to improve voltage-controlled flexibility ratio.
Further, objective function is indicated with following formula in the Optimized model:
Min F=α τ (Δ Pac+ΔPdc)+hcΔx
In formula, α is electric energy electricity price, and τ is optimization time span, Δ PacTo exchange active loss, Δ PdcIt is active for direct current
Loss, hcFor Readjusting cost coefficient, F is the ac and dc systems operating cost comprising flexible DC transmission；
Δ x is the variable quantity of reactive compensation switching group number:
Δ x=| C-C0|
Wherein, C indicates the column vector of current method of operation reactive compensation switching group number, C0For previous method of operation switching
The column vector of group number.
Further, the determination that variable is controlled in the objective function must satisfy the power flow equation of system, own simultaneously
Variable should also meet respective bound inequality constraints.
Further, the Optimized model application genetic algorithm is solved, in solution:
The objective function being optimal, i.e. the sum of Web-based exercise and Reactive-power control amount cost will be wished, as genetic algorithm
Fitness function；
Each combination for controlling variable is an individual, carries out Load flow calculation to the corresponding system of each individual, if
Power flow solutions convergence, then show that corresponding individual is feasible solution, and then substitutes into objective function, seeks its fitness function value；If
It does not restrain, then gives up the individual；
All convergent individual composition populations selects fitness function value lower individual as parent from population, into
" intersection " and " variation " operation in row genetic algorithm meaning, obtains progeny population, judges whether progeny population meets convergence limit
Condition processed, is such as unsatisfactory for, then iteration process, until progeny population meets convergence restrictive condition.
Further, to meet actual optimization model needs, and solution efficiency is improved, the present invention is to traditional genetic algorithm
Coding mode, mutation operator and constraint conditional processing method are improved:
1) selection of coding mode uses integer and real number hybrid coding mode, and reactive compensation switching group number is compiled using integer
Code mode, flexible HVDC transmission system inject the active and idle of AC system and use real coding mode, control the volume of variable
Code is as follows:
X=[C | Pref|Qref]=[C1,C2,...,Cp|P1ref,P2ref,...,Pqref|Q1ref,Q2ref,...,Qqref]
In formula, C indicates reactive compensation switching group number, PrefAnd QrefRespectively indicate inverter injection AC system active and
Reactive power, p, q phase should be candidate compensation buses number and inverter number of nodes.
According to reactive compensation switching group number, the susceptance value B of compensating electric capacity can be derivedi:
In formula,For reactive compensation switching step-length.
2) in idle work optimization, inverter injects the active-power P of AC systemref, reactive power QrefAnd reactive compensation
Switching group number C is the control variable of constraint certainly, and the specified apparent energy constraint of inverterIt needs as penalty term,
It is added to objective function fQIn, obtain revised solution objective function FQ:
In formula, λ is penalty factor, SiFor the apparent energy of every inverter in iterative solution pilot process, Sat (x) is
Saturation function.
λ=gen λ0
In formula, λ0For penalty factor initial value, gen is evolutionary generation, that is, number of iterations, Simin、SimaxFor the specified view of inverter
In power minimum, maximum value.
Objective function is as fitness evaluating function, for assessing the quality of solution, when penalty factor linearly increases with the number of iterations
Added-time, any infeasible solution more than boundary all can be eliminated gradually by the competition process of genetic algorithm, and meet penalty termFeasible solution left.
3) in solving, using improved mutation algorithm, aberration rate is gradually reduced with the increase of evolutionary generation, is no more than simultaneously
Preset minimum aberration rate:
In formula, PmFor aberration rate, Pm0It is aberration rate initial value, PmstepIt is that aberration rate reduces step-length, t is iterative evolution generation
Number, t0It is preset turnover algebra, PmminIt is preset minimum aberration rate.
Disclosed herein as well is the island operation of power networks optimization systems based on multiterminal flexible direct current, comprising:
Optimization mould establishes unit, establishes the ac grid voltage Optimized model based on multiterminal flexible direct current, the Optimized model
Objective function in addition to traditional transmission loss index, further include economic cost needed for Reactive-power control；
The active power of inverter injection AC system and reactive power are considered as control variable, benefit by variable determination unit
Active ability is actively adjusted with VSC, optimizes distribution of the active power between parallel ac and dc circuit, to indirectly control nothing
Function flowing；VSC is actively adjusted to idle ability to put into operation as the reactive compensation means of continuously adjustable, optimizes capacitor
Group switching frequency, meanwhile, control variable should also include the switching group number of compensating electric capacity, and state variable is then generator output and is
It unites each node voltage；
Model solution unit, using Revised genetic algorithum to solve Optimized model, it is contemplated that compensating electric capacity is discrete magnitude,
And soft straight active reactive is continuous quantity, in solution by the way of integer and real number hybrid coding；Penalty term is introduced into target
In function, to handle inequality constraints condition；Gradually reduced using with evolutionary generation increase, at the same be no more than it is preset most
The mutation algorithm of small aberration rate.
Compared with prior art, the beneficial effects of the present invention are:
Flexible HVDC transmission system is utilized the invention proposes a kind of, improves the innovative approach of island operation of power networks optimization.
Active and idle ability is actively adjusted this process employs VSC, electricity when will reduce active power loss and grid operation mode switching
The economic cost of container group switching is as optimization aim.The characteristics of for the model, coding of the present invention to traditional genetic algorithm
Mode, mutation operator and constraint conditional processing method are improved, and are proposed a kind of Revised genetic algorithum and are solved, and
The realistic case of Zhoushan Multi-end flexible direct current transmission demonstration project is relied on to carry out simulation analysis.Simulation results show the having of method
Effect property and reasonability show that the model has certain meaning to the wattles power economic equivalent containing soft lineal system, have good answer
Use prospect.
Detailed description of the invention
The accompanying drawings constituting a part of this application is used to provide further understanding of the present application, and the application's shows
Meaning property embodiment and its explanation are not constituted an undue limitation on the present application for explaining the application.
Fig. 1 is the general idea flow diagram of the embodiment of the present application；
Fig. 2 is that the embodiment of the present application application genetic algorithm carries out solution schematic diagram.
Specific embodiment
It is noted that following detailed description is all illustrative, it is intended to provide further instruction to the application.Unless another
It indicates, all technical and scientific terms used herein has usual with the application person of an ordinary skill in the technical field
The identical meanings of understanding.
It should be noted that term used herein above is merely to describe specific embodiment, and be not intended to restricted root
According to the illustrative embodiments of the application.As used herein, unless the context clearly indicates otherwise, otherwise singular
Also it is intended to include plural form, additionally, it should be understood that, when in the present specification using term "comprising" and/or " packet
Include " when, indicate existing characteristics, step, operation, device, component and/or their combination.
The foundation of Optimized model mainly includes selection control variable, construction objective function and determining constraint condition three parts.
Wherein, control variable is one group of variable that can be adjusted and control in model；Objective function is retouched to the quantization of optimization aim
It states；Constraint condition is a series of equatioies or inequality, reflects and controls the constraint that variable is subject in model.Based on different control
Variable-value can uniquely determine the method for operation of system in conjunction with given datas such as system power generation, load and network structures.No
Under the same method of operation, target function value is different, and in general, optimization aim is to keep target function value minimum or maximum.Optimization
The process of model solution is exactly to find out the process for keeping target function value optimal by derivation algorithm, and guarantee that controlling variable takes
The combination of value is within the scope of constraint condition.Compared with the system before optimization, in optimizing index, (such as network damages the system after optimization
Consumption, economical operation cost etc.) on perform better than.
As shown in Figure 1, in the application on the whole, initially setting up Optimized model, selection control variable constructs objective function,
It determines constraint condition, then solving model, is solved using Revised genetic algorithum when solution, carry out emulation point for solving result
Analysis and assessment, the benefit of last Integrated Evaluation Model.
It is proposed of the invention combines the practical difficulty of island power grid in operation, transmits electricity and charges such as long range submarine cable
Power is larger, and grid structure is relatively weak, and adjustment nargin is limited and load peak valley is obvious, and operation characteristic changes greatly.Mould
The foundation of type mainly includes selection control variable, construction objective function and determining constraint condition three parts: by multiterminal flexible direct current
Active and idle control ability introduce ac grid voltage optimization, select inverter injection AC system active and idle function
Rate is used as control variable, meanwhile, control variable should also include the switching group number etc. of compensating electric capacity；Consider generator terminal voltage tune
When section, grid operation mode switching reactive-load compensation equipment switching etc. operate brought by regulating economy cost, by cost of losses and
Readjusting cost expense is integrated by certain coefficient ratio, with the minimum target of totle drilling cost, constructs objective function；In model, respectively
The determination of control variable must satisfy system load flow equation, need to meet the constraint of power-balance, inverter inside direct current system
The variables such as active reactive reference value, each node voltage also should be in upper and lower limits, and in summary limiting factor, provides constraint item
Part.
Compared with Traditional DC, it is exactly using the voltage based on controllable shutdown device that one of flexible direct current, which significantly indicates,
Source inverter (VSC), this is provided with flexible direct current actively to adjust active and idle ability, is that the voltage of AC network is excellent
Change control and provides new thinking.Based on this characteristic, optimize network voltage using flexible direct current the invention proposes a kind of, and
Take into account the model for reducing active power loss and optimizing capacitor group switching number.
Active control feature based on VSC: with the line commutation inverter (LCC) in conventional high-tension direct current based on thyristor
Compare, the basic sexual clorminance that VSC has be the device used in it be it is two-way controllable, be reflected on output voltage U, will appear as
Output voltage amplitude U and phase δ is controllable.Therefore, from the perspective of AC system, VSC can be equivalent to a nothing
The motor or generator of rotary inertia almost can instantaneously realize active power and idle in four quadrants of PQ plane
The independent control of power.
Idle work optimization is the nonlinear programming problem of multivariable multiple constraint, and variable is divided into control variable and state variable two
Seed type.The active reactive control ability of multiterminal flexible direct current is introduced into ac grid voltage optimization, being equivalent to can be by the change of current
The active-power P of device injection AC systemrefAnd reactive power QrefIt is considered as control variable.The present invention is ground to this characteristic
On the basis of studying carefully, the ac grid voltage Optimized model based on multiterminal flexible direct current is proposed.
Utilize the running optimizatin strategy of VSC: under normal operation, direct current system meeting and alternating current circuit arranged side by side therewith are total
It is same to undertake conveying task.In alternating current-direct current coordinate system, the transmission power distribution between ac and dc circuit often lacks enough
Foundation.Power distribution is only often carried out according to operating experience in management and running, therefore, it is difficult to predict the benefit of allocation plan and band
The consequence come.In fact, the transmission power of flexible HVDC transmission system can be with active control, in other words, as long as determining
Active power controller instruction value Pref, that is, can determine the power distribution between AC/DC parallel route.If the P of inverterrefSetting
It is too low, it cannot fully utilize the advantages such as the DC line low-loss of flexible DC transmission technology, transmission power be controllable；Phase
Instead, if the P of inverterrefIt is arranged excessively high, in fact it could happen that AC/DC parallel route transmission power flows to opposite situation (referred to as
" circulation arranged side by side "), it is unfavorable for normal electricity scheduling, increases the probability that DC equipment breaks down to a certain extent.This hair
It is bright that VSC inverter is actively adjusted into the ability of active power as active control amount, to PrefReasonably it is arranged.By dividing
Flowing with active power between parallel ac and dc circuit achievees the purpose that indirectly control idle flowing.
VSC inverter, which has, actively adjusts idle ability, this is functionally with devices such as reactive compensation capacitor and SVC
There are similitudes.For island power grid since load or burden without work variation is obvious, the method for operation is changeable, needs more frequently being to idle benefit
It repays the equipment such as capacitor and carries out switching operation.And the operation each time of equipment can all increase its damaged condition, influence its service life,
Expense equivalent to increase investment and operation and maintenance.That is, carrying out optimal reactive power dispatch is to need certain economic cost
's.If VSC inverter is actively adjusted idle ability to be used, thrown as the reactive compensation means of continuously adjustable
Enter operation, to a certain extent, may be implemented to have complementary functions with traditional reactive-load compensation equipment.On the one hand, capacitor can be optimized
Device group switching frequency reduces switching cost；On the other hand, the selection of voltage control approach can also be extended, voltage control is improved
Flexibility ratio, and then improve voltage level.
In conclusion the characteristics of VSC independent control active reactive, provides feasibility for the running optimizatin of island power grid, it can
To mitigate the pressure of reactive-load compensation equipment frequent switching.The method of operation using flexible direct current optimization island power grid is that there are feasible
Property.
About objective function: as described above, the adjusting of optimal reactive power dispatch needs additional cost.Therefore, considering electricity
When net idle work optimization, other than needing using loss minimization as optimization aim, it is also necessary to further consider transformer and reactive compensation
The expense of the frequent equivalence of equipment.In addition, flexible DC transmission route and alternating current circuit shared one arranged side by side
Fixed active power conveys task, if the active power transfer of direct current system changes, the wattful power of alternating current circuit in parallel
Rate transmission can also change.Therefore, when adjusting direct current system active power, need to comprehensively consider the influence of various aspects.
It to sum up analyzes, for the alternating current-direct current paired running system comprising flexible DC transmission, in conjunction with operating cost minimum
It can be represented by the formula with the idle work optimization objective function for considering Readjusting cost:
MinF=α τ (Δ Pac+ΔPdc)+hcΔx (1)
In formula (1), α is electric energy electricity price, and τ is optimization time span, Δ PacTo exchange active loss, Δ PdcFor direct current
Active loss, hcFor Readjusting cost coefficient, F is that the alternating current-direct current paired running systematic running cost comprising flexible DC transmission is used.
Δ x is the variable quantity of reactive compensation switching group number:
Δ x=| C-C0| (2)
Wherein, C indicates the column vector of current method of operation reactive compensation switching group number, C0For previous method of operation switching
The column vector of group number.
The active reactive control ability of multiterminal flexible direct current is introduced into ac grid voltage optimization, inverter can be injected
The active power and reactive power of AC system are considered as control variable.Meanwhile controlling variable should also include the switching of compensating electric capacity
Group number etc..State variable is then generator output and each node voltage of system etc..
Variable and its constraint condition in above-mentioned objective function: in optimization process, the determination for controlling variable, which must satisfy, is
The power flow equation (3) of system, while all variables should also meet respective bound inequality constraints.
Wherein, n is system node number, PGiAnd QGiFor the active and idle power output of system generator node, PaciAnd QaciFor
The load active power and reactive power of node i, PirefAnd QirefFor the active and reactive power of direct current system access node.When
When inverter absorbs idle from node, QirefTake positive value；When inverter is idle to AC system output, QirefTake negative value.Qci
For the reactive compensation capacity of node i, GijAnd BijThe respectively conductance and susceptance of node admittance matrix i row j column element, ViAnd VjFor
The voltage of node i, j, VijAnd θijVoltage magnitude and phase angle between node i, j, Vi、VjRespectively node i, j voltage,
QaciFor the reactive load power of node i.
In Multi-end flexible direct current transmission system, the active power of each inverter conveying should meet equilibrium relation.For being
M (m >=3) a inverter of system, should meet:
Control the inequality constraints of variable:
In formula, SirefIt is inverter in the specified apparent energy of node i, that is, works asWhen, inverter itself is
Allow to run.CmaxAnd CminFor the bound of reactive compensation switching group number.
The inequality constraints of state variable:
In formula, Vimax、ViminFor the bound of node voltage, PGimax、QGimax, with PGimin、QGiminRespectively generator goes out
The bound of power.
The method for solving of above-mentioned model: above-mentioned Optimized model is nonlinear and multiple extremum, and contains discrete variable.Needle
To this model, the present invention changes the coding mode of traditional genetic algorithm, mutation operator and constraint conditional processing method
Into proposing a kind of Revised genetic algorithum and solved.
The general step of genetic algorithm is as shown in Figure 2.In solution, it would be desirable to be optimal the target letter of (minimum value)
Number, i.e. the sum of Web-based exercise and Reactive-power control amount cost, the fitness function as genetic algorithm.Control each group of variable
Closing is an individual.Load flow calculation is carried out to the corresponding system of each individual, if power flow solutions are restrained, shows corresponding
Body is feasible solution, and then is substituted into objective function, its fitness function value is sought；If not restraining, which is given up.All receipts
The individual composition starting population held back.It selects the lower individual of fitness function value as parent from population, carries out genetic algorithm
" intersection " and " variation " operation in meaning, obtains progeny population.Judge whether progeny population meets convergence restrictive condition, it is such as full
Sufficient then calculating terminates；It is such as unsatisfactory for, then the convergent progeny population of trend is considered as to the starting population of next iteration, iteration
Process.
Coding mode: selecting suitable coding mode is that the premise of idle work optimization is solved using genetic algorithm.Its direct shadow
Ring adaptability, the speed and precision of algorithm.Since compensation switching group number is discrete magnitude, and soft straight active reactive is continuous
Amount.Therefore, herein use integer and real number hybrid coding mode, randomly selected compensation equipment switching group number integer coding,
It is soft straight active and without function real coding.The coding for controlling variable can be as follows:
In formula, C indicates reactive compensation switching group number, PrefAnd QrefRespectively indicate inverter injection AC system active and
Reactive power, p, q phase should be candidate compensation buses number and inverter number of nodes.
According to capacitor investment group number, the susceptance value B of compensating electric capacity can be derivedi:
In formula,Step-length is put into for reactive compensation.
The processing of constraint condition: in most of nonlinear optimal problem, inequality constraints adds usually as penalty term
Extension objective function is constituted into objective function.Since genetic algorithm is a kind of no contained optimization algorithm, handled by penalty term
It constrains most suitable.In idle work optimization, inverter injects the active-power P of AC systemref, reactive power QrefWith idle benefit
The control variable that switching group number C is constraint certainly is repaid, and the specified apparent energy of inverter constrainsIt needs as punishment
, it is added to objective function fQIn, obtain revised solution objective function FQ。
In formula, λ is penalty factor, SiFor the apparent energy of every inverter in iterative solution pilot process, Sat (x) is
Saturation function.
λ=gen λ0 (12)
In formula, λ0For penalty factor initial value, gen is evolutionary generation (number of iterations), Simin、SimaxFor the specified view of inverter
In power minimum, maximum value.
In the algorithm, objective function is as fitness evaluating function, for assessing the quality of solution.When penalty factor is with iteration time
When number is linearly increasing, any infeasible solution more than boundary all can be eliminated gradually by the competition process of genetic algorithm, and meet
Penalty termFeasible solution left.Originally penalty factor value very little allows in initial solution group
Although some solutions be it is infeasible, may imply the portion gene of optimization solution, it is not from feasible optimization solution in other words
It is remote, if imposing on severe punishment immediately, generate barrier effect, it is possible to lead to the loss of effective information in group.Gradually
The penalty factor of increase had not only avoided the loss of effective information, but also induction search jumps out of infeasible solution space, achievees the purpose that optimizing.
The improvement of genetic operator: mutation operator is to the diversity for maintaining population and precocity is inhibited to play an important role.Variation
Rate is excessive to be easy to cause random search, too small, the ability that can weaken generation new individual, inhibit precocity.Herein using with generation of evolving
Number, which increases, to be gradually reduced, while being no more than the mutation algorithm of preset minimum aberration rate.
In formula, PmFor aberration rate, Pm0It is aberration rate initial value, PmstepIt is that aberration rate reduces step-length, t is iterative evolution generation
Number, t0It is preset turnover algebra, PmminIt is preset minimum aberration rate.
Genetic algorithm is a kind of iterative algorithm, " variation " operation be genetic algorithm in each iteration, to obtain more preferably
Objective function and to the operation that is changed of control variable.Here mutation operator is improved, main purpose is to improve model solution effect
Rate.
In fact, variation is to adjust on the original basis by shelves, with change for most of discrete control variable
Different progress, population are tended towards stability, and variable should be made as far as possible to change in the smaller range of current value, to improve variation effect
Rate.Therefore, when evolving beginning, aberration rate PmLarger, population variation is more violent, increases the otherness inside population, with
The probability for covering optimal solution is improved as wide as possible, inhibits precocious phenomenon.With the progress of evolution, population is gradually to optimal solution
Convergence nearby, aberration rate PmReduce.In the latter stage of evolution, PmA reduced levels are maintained, to avoid unit control amount optimal
Solution oscillates about, and program is made to be mistaken for the case where not restraining.
In order to enable those skilled in the art can clearly understand the technical solution of the application, below with reference to tool
The technical solution of the application is described in detail in the embodiment and comparative example of body.
Zhoushan power grid is typical island power grid, is limited by geographical conditions, and northern island rack is weak, each island and sheet
Grid contact is weaker between island and island, and supports without big power supply, and power supply reliability and operational flexibility are lower.Zhoushan
Multi-end flexible direct current transmission demonstration project is first five ends flexible DC transmission engineering in world wide, the formal investment in 2014
It uses, DC voltage level 200kV.However, in actual use, AC and DC system is substantially at respectively independently operated
State limits the performance of VSC voltage regulatory function.
By taking the Zhoushan power grid containing five end flexible HVDC transmission systems as an example, optimization program is write with matlab, utilizes improvement
Genetic algorithm analyzes the representative instance of Zhoushan power grid.
Basic parameter: Zhoushan power grid 110kV and the above node share 106, wherein compensation capacitor node 54, the change of current
Tiny node 5.
In this example, VSC, which is pressed, determines active power, determines Reactive Power Control.Control variable totally 59, including 49 exchanges
Node compensation device switching amount (discrete control variable), amount that 5 inverter nodes are idle and 5 active amounts of inverter node are (even
Continuous control variable).Compensating node voltage range is 0.9~1.1 (per unit value).Each substation is limited by construction scale, idle
There are bound constraints for adjustable range.Wherein, every group of transformer of 500 kv substations it is idle configuration by 2 group capacitors (2 ×
60Mvar), 2 groups of reactors (2 × 60Mvar) consider.Every group of 6 group capacitor of transformer configuration of 220 kv substations (6 ×
10Mvar), 3 groups of reactors (3 × 10Mvar)；Every group of 6 group capacitor of transformer configuration of 110 kv substations (6 ×
4.8Mvar)。
In the selection of load parameter, the method for operation for choosing peak load, waist lotus, paddy lotus these three successively transition is begged for
By.Wherein, it is the 45% of peak load that load when waist lotus, which is the load of 60%, Gu Heshi of peak load,.
In terms of regulating economy cost, with reference to the current capacitor switching situation of Zhoushan power grid, every group of shunt capacitor is considered
Maximum switching frequency about 1000 times, the service life about 20 years of year.In terms of Web-based exercise, about 0.5 yuan/kilowatt hour of electricity price is considered, according to
Twice between adjustment, the average eguivalent operation duration of every route is to calculate for 1000 hours.
Improved adaptive GA-IAGA parameter population scale NIND=300, maximum genetic algebra MAXGEN=1000.
Interpretation of result: will be soft straight as reactive source, when participating in voltage optimization in the form of controlling reactive power, corresponding peak-
Waist mode changes to be changed with waist-paddy mode, and idle work optimization result and total economic cost are shown in Table 1, table 2.
1 VSC of table participates in peak-waist mode idle work optimization result before and after voltage optimization
2 VSC of table participates in waist-paddy mode idle work optimization result before and after voltage optimization
By it is soft it is straight actively adjust active ability and be equally used as active control amount, adjust active power in parallel alternating current-direct current line
Distribution between road, and then idle flowing is indirectly controlled, it can effectively expand the range of Optimizing Search, improve effect of optimization.This
When, corresponding peak-waist mode changes to be changed with waist-paddy mode, and idle work optimization result and total economic cost are shown in Table 3, table 4.
3 VSC of table participates in peak-waist mode idle work optimization result before and after voltage optimization
4 VSC of table participates in waist-paddy mode idle work optimization result before and after voltage optimization
The result from table it can be concluded that, if it is soft it is straight only participate in voltage optimization as reactive source, corresponding peak-waist mode change and
Waist-paddy mode changes, and total economic cost is respectively 314.84 ten thousand yuan and 192.33 ten thousand yuan, with it is soft be directly not involved in optimization when compared with,
12.18% and 18.76% are reduced respectively.If straight actively adjusting active ability by soft and being equally used as active control amount, phase
The total economic cost answered is respectively 302.58 ten thousand yuan and 174.38 ten thousand yuan, reduces 15.61% and 26.34% respectively, and soft straight
Only as reactive source participate in optimization when compare, reduce 3.89% and 9.33% respectively, with it is soft directly be not involved in optimization when compared with, point
15.61% and 26.34% are not reduced.As it can be seen that it is soft directly after active and idle both sides regulating power taking full advantage of,
Total economic cost has biggish reduction compared with conventional voltage optimization.
By Case Simulation, the active reactive independent control characteristic for demonstrating flexible direct current system can be applied to the present invention
In the network voltage running optimizatin of island, Optimized model has the feasibility in engineering.Alleviating reactive-load compensation equipment frequent switching
Pressure can also on the whole, to the performance driving economy and electricity of area power grid while improving voltage-controlled flexibility
Pressure stability is made contributions.
The foregoing is merely preferred embodiment of the present application, are not intended to limit this application, for the skill of this field
For art personnel, various changes and changes are possible in this application.Within the spirit and principles of this application, made any to repair
Change, equivalent replacement, improvement etc., should be included within the scope of protection of this application.
Claims (10)
1. the island operation of power networks optimization method based on multiterminal flexible direct current, characterized in that include:
The ac grid voltage Optimized model based on multiterminal flexible direct current is established, the objective function of the Optimized model removes traditional net
It damages outside index, further includes economic cost needed for Reactive-power control；
The active power of inverter injection AC system and reactive power are considered as control variable, actively adjusted using VSC active
Ability, optimize distribution of the active power between parallel ac and dc circuit, to indirectly control idle flowing；Actively by VSC
The reactive compensation means that idle ability is adjusted as continuously adjustable put into operation, optimize capacitor group switching number, meanwhile,
Controlling variable should also include the switching group number of compensating electric capacity, and state variable is then generator output and each node voltage of system；
Using Revised genetic algorithum to solve Optimized model, it is contemplated that compensating electric capacity is discrete magnitude, and soft straight active reactive
It is continuous quantity, in solution by the way of integer and real number hybrid coding；Penalty term is introduced into objective function, is differed with processing
Formula constraint condition；It is gradually reduced using with evolutionary generation increase, while the variation for being no more than preset minimum aberration rate is calculated
Method.
2. the island operation of power networks optimization method based on multiterminal flexible direct current as described in claim 1, characterized in that described excellent
Change objective function in model is indicated with following formula:
Min F=α τ (Δ Pac+ΔPdc)+hcΔx
In formula, α is electric energy electricity price, and τ is optimization time span, Δ PacTo exchange active loss, Δ PdcFor direct current active loss,
hcFor Readjusting cost coefficient, F is the ac and dc systems operating cost comprising flexible DC transmission；
Δ x is the variable quantity of reactive compensation switching group number:
Δ x=| C-C0|
Wherein, C indicates the column vector of current method of operation reactive compensation switching group number, C0For previous method of operation switching group number
Column vector.
3. the island operation of power networks optimization method based on multiterminal flexible direct current as claimed in claim 2, characterized in that the mesh
The determination that variable is controlled in scalar functions must satisfy the power flow equation of system, while all variables should also meet respective bound
Inequality constraints.
4. the island operation of power networks optimization method based on multiterminal flexible direct current as described in claim 1, characterized in that described
Optimized model application genetic algorithm is solved, in solution:
The objective function being optimal, i.e. the sum of Web-based exercise and Reactive-power control amount cost will be wished, as the suitable of genetic algorithm
Response function；
Each combination for controlling variable is an individual, Load flow calculation is carried out to the corresponding system of each individual, if trend
As a result it restrains, then shows that corresponding individual is feasible solution, and then substitute into objective function, seek its fitness function value；If not receiving
It holds back, then gives up the individual；
All convergent individual composition populations, select the lower individual of fitness function value as parent from population, are lost
" intersection " and " variation " operation in propagation algorithm meaning, obtains progeny population, judges whether progeny population meets convergence limitation item
Part is such as unsatisfactory for, then iteration process, until progeny population meets convergence restrictive condition.
5. the island operation of power networks optimization method based on multiterminal flexible direct current as claimed in claim 4, characterized in that tradition
Coding mode, mutation operator and the constraint conditional processing method of genetic algorithm improve:
The selection of coding mode uses integer and real number hybrid coding mode, and reactive compensation switching group number uses integer coding side
Formula, flexible HVDC transmission system inject the active and idle of AC system and use real coding mode, control the coding of variable such as
Shown in lower:
X=[C | Pref|Qref]=
[C1,C2,...,Cp|P1ref,P2ref,...,Pqref|Q1ref,Q2ref,...,Qqref]
In formula, C indicates reactive compensation switching group number, PrefAnd QrefRespectively indicate the active and idle of inverter injection AC system
Power, p, q phase should be candidate compensation buses number and inverter number of nodes.
6. the island operation of power networks optimization method based on multiterminal flexible direct current as claimed in claim 5, characterized in that according to nothing
Function compensates switching group number, can derive the susceptance value B of compensating electric capacityi:
In formula,For reactive compensation switching step-length.
7. the island operation of power networks optimization method based on multiterminal flexible direct current as claimed in claim 5, characterized in that idle
In optimization, inverter injects the active-power P of AC systemref, reactive power QrefIt is to constrain certainly with reactive compensation switching group number C
Control variable, and inverter specified apparent energy constraintIt needs to be added to objective function f as penalty termQIn,
Obtain revised solution objective function FQ:
In formula, λ is penalty factor, SiFor the apparent energy of every inverter in iterative solution pilot process, Sat (x) is saturation letter
Number.
λ=gen λ0
In formula, λ0For penalty factor initial value, gen is evolutionary generation, that is, number of iterations, Simin、SimaxIt is the specified view of inverter in function
Rate minimum value, maximum value.
8. the island operation of power networks optimization method based on multiterminal flexible direct current as claimed in claim 7, characterized in that target letter
Number is used as fitness evaluating function, and for assessing the quality of solution, when penalty factor is linearly increasing with the number of iterations, any is more than side
The infeasible solution on boundary all can be eliminated gradually by the competition process of genetic algorithm, and meet penalty termIt is feasible
Solution is left.
9. the island operation of power networks optimization method based on multiterminal flexible direct current as described in claim 1, characterized in that solve
In, using improved mutation algorithm, aberration rate is gradually reduced with the increase of evolutionary generation, while being no more than preset minimum
Aberration rate:
In formula, PmFor aberration rate, Pm0It is aberration rate initial value, PmstepIt is that aberration rate reduces step-length, t is iterative evolution algebra, t0
It is preset turnover algebra, PmminIt is preset minimum aberration rate.
10. the island operation of power networks optimization system based on multiterminal flexible direct current, characterized in that include:
Optimization mould establishes unit, establishes the ac grid voltage Optimized model based on multiterminal flexible direct current, the mesh of the Optimized model
Scalar functions further include economic cost needed for Reactive-power control in addition to traditional transmission loss index；
The active power of inverter injection AC system and reactive power are considered as control variable, utilize VSC by variable determination unit
Active ability is actively adjusted, optimizes distribution of the active power between parallel ac and dc circuit, to indirectly control idle stream
It is dynamic；VSC is actively adjusted to idle ability to put into operation as the reactive compensation means of continuously adjustable, optimization capacitor group is thrown
Number is cut, meanwhile, control variable should also include the switching group number of compensating electric capacity, and state variable is then that generator output and system are each
Node voltage；
Model solution unit, using Revised genetic algorithum to solve Optimized model, it is contemplated that compensating electric capacity is discrete magnitude, and soft
Straight active reactive is continuous quantity, in solution by the way of integer and real number hybrid coding；Penalty term is introduced into objective function
In, to handle inequality constraints condition；It is gradually reduced using with evolutionary generation increase, while being no more than preset minimum change
The mutation algorithm of different rate.
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