CN113541191A - Multi-time scale scheduling method considering large-scale renewable energy access - Google Patents
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Abstract
The invention provides a multi-time scale scheduling method considering large-scale renewable energy access, which comprises the following steps: s1, forecasting the day-ahead output upper and lower limits of the renewable energy through the probability distribution of the day-ahead forecasting error of the renewable energy, and constructing a robust uncertain set; s2, constructing a two-stage robust scheduling model of the power distribution network and the multi-microgrid system, wherein the two-stage robust scheduling model comprises a day-ahead stage model and a regulation and control stage model; s3, splitting a day-ahead robust scheduling problem into major and minor problems through a column constraint generation algorithm based on a day-ahead stage model, and iteratively solving to obtain an optimal day-ahead scheduling decision of the power distribution network and the multi-microgrid system in the worst scene; and S4, based on the regulation and control stage model, on the basis of the optimal day-ahead scheduling decision, performing rolling optimization on the day-ahead scheduling of the power distribution network and the multi-microgrid system by adopting a day-ahead rolling optimization algorithm, and realizing multi-time scale scheduling of the power distribution network and the multi-microgrid system.
Description
Technical Field
The invention relates to the technical field of power scheduling, in particular to a multi-time-scale scheduling method considering large-scale renewable energy access.
Background
With the rapid development and the large-scale application of the renewable energy distributed power generation technology, the micro-grid is receiving wide attention as an effective access mode of a distributed power supply. The micro-grid group coordinates energy management of adjacent distributed units, micro-grids and loads in a region, so that the permeability of a distributed power supply can be improved, and the efficient utilization of renewable energy sources is realized. Due to the fluctuation of the output of the renewable energy sources, the large-scale access of the distributed renewable energy sources can bring challenges to the operation and scheduling of the power distribution network and the multi-microgrid system. In the scheduling research of a power distribution network and multiple micro-grids considering the uncertainty of renewable energy sources, the random optimization is difficult to cope with extreme scenes; the opportunity constraint method needs a large amount of data and is difficult to solve; robust optimization enables scheduling robustness, but its day-ahead decisions are too conservative. In addition, the scheduling models are all scheduling for the day-ahead scale, and because the prediction error of the day-ahead renewable energy is larger than the prediction error in the day, the accuracy of the scheduling models used in actual scheduling is poor, and the scheduling models need to be adjusted on the basis of the day-ahead scheduling.
Disclosure of Invention
The invention aims to provide a multi-time scale scheduling method considering large-scale renewable energy access, which is used for scheduling large-scale renewable energy accessed to a power distribution network and a multi-microgrid system in two scales of day-ahead and day-within. In the day-ahead scheduling, the power distribution network and the multi-microgrid system predict the output of the renewable energy within 24 hours in the future, and system scheduling personnel arrange a system day-ahead scheduling plan according to day-ahead prediction information; due to the fact that the prediction error is large day ahead, day-in-day real-time scheduling is conducted on the basis of day-ahead scheduling in order to accurately reflect the fluctuation of the output of the renewable energy. And the in-day scheduling updates the renewable energy in-day output predicted value in a plurality of time intervals in the future in a rolling mode through ultra-short-term (generally less than 1 hour) prediction, and the scheduling center performs economic scheduling on the real-time output of each controllable unit at the next moment based on the in-day output predicted value.
In order to achieve the above object, the present invention provides a multi-time scale scheduling method considering large-scale renewable energy access, which is suitable for a power distribution network and a multi-microgrid system, and comprises the steps of:
s1, forecasting the day-ahead output upper and lower limits of the renewable energy through the probability distribution of the day-ahead forecasting error of the renewable energy, and constructing a robust uncertain set;
s2, constructing a two-stage robust scheduling model of the power distribution network and the multi-microgrid system; the two-stage robust scheduling model comprises a day-ahead stage model and a regulation and control stage model; the day-ahead stage model makes a day-ahead scheduling decision based on the output of renewable energy predicted day-ahead; the regulation and control stage model identifies the worst scene of the output of the renewable energy sources based on the day-ahead scheduling decision, and corrects the day-ahead scheduling decision aiming at the worst scene;
s3, splitting a day-ahead robust scheduling problem into main and sub problems through a column constraint generation algorithm, and iteratively solving to obtain an optimal day-ahead scheduling decision of the power distribution network and the multi-microgrid system in the worst scene;
and S4, performing rolling optimization on the day-to-day scheduling of the power distribution network and the multi-microgrid system by adopting a day-to-day rolling optimization algorithm on the basis of the optimal day-to-day scheduling decision, and realizing multi-time scale scheduling of the power distribution network and the multi-microgrid system.
Optionally, step S1 includes:
s11, orderThe maximum positive and negative prediction error of the output of the nth renewable energy source set,predicting an error of the output of the nth renewable energy unit before the day; according toRespectively obtaining the lambda quantile and the 1-lambda quantile of the cumulative probability density functionWherein lambda is a preset value;
s12, representing the uncertainty of the renewable energy contribution as:
whereinThe actual output of the nth renewable energy source unit is obtained;predicting output for the nth renewable energy unit in the day ahead;
Optionally, the objective function of the day-ahead stage model is:
wherein i and j represent the node number of the power distribution network; t is the total scheduling time interval; t represents the current scheduling time; ij is a power distribution network line between the ith power distribution network node and the jth power distribution network node; f. ofda1Scheduling cost for the power distribution network and the multi-microgrid system day ahead; f. ofda2For distribution network and many microgrid systemsRegulating and controlling cost; x is a day-ahead scheduling decision variable; y is a regulation decision variable; xi is an uncertain variable; k is the number of the micro-grid; n is a radical ofMGThe number of the micro-grids; ctr、Closs、CIDRRespectively obtaining unit electricity purchasing cost, distribution network loss cost and distribution network node load demand response cost of the slave main network of the distribution network; cre、CesRespectively discarding a punishment coefficient of renewable energy resources and a punishment coefficient of energy storage loss cost for the micro-grid;purchasing power from a main network for the power distribution network;the output of a gas turbine in the kth micro-grid is obtained; i isk,tIs [0,1 ]]The internal variable represents the output state variable of the gas turbine unit in the kth micro-grid; dj,tThe translatable load power of the j distribution network node at the scheduling time t before the demand response;the translatable load power of the j distribution network node at the scheduling time t after the demand response;the renewable energy power is abandoned for the kth micro-grid;the square of the line current of the power distribution network; r isijIs a line resistance; omegaPE、ΩTRRespectively a power distribution network line set and a power distribution network transformer node set;charging power and discharging power for stored energy respectively; a isk、bk、ckRespectively, gas turbine output cost coefficients;
the objective function of the regulation phase model is: realizing distribution network and multi-network under determined day-ahead scheduling decisionRegulation and control cost f of micro-grid system in worst renewable energy output sceneda2And minimum.
Optionally, the constraint conditions of the day-ahead phase model include: a main grid output constraint, a gas turbine minimum start/shut down time constraint, a tie line power transmission constraint;
the primary grid output force constraints include:
whereinTransmitting reactive power for the main network;respectively transmitting upper and lower limits of reactive power for the main network;and transmitting upper and lower limits of active power for the main network.
The gas turbine minimum on/off time constraints include:
wherein the content of the first and second substances,the minimum starting time and the minimum closing time of the unit.
The tie-line power transfer constraints include
Wherein the content of the first and second substances,transmitting power to the kth micro-grid for the power distribution network;respectively the lower limit and the upper limit of the transmission power between the micro-grid and the distribution network.
Optional, objective function f of the intraday roll optimization algorithmdiComprises the following steps:
wherein, tinA step size optimized for rolling in days; PF is an energy storage penalty item; pf is a penalty coefficient;the energy storage charge capacity obtained by day-ahead scheduling.
Optionally, the constraint condition of the rolling optimization algorithm in the day is the same as the constraint condition of the regulation phase model, and includes: the method comprises the following steps of power distribution network power flow constraint, power distribution network safety constraint, static reactive compensator constraint, gas turbine output constraint, micro-grid power balance constraint, energy storage charging and discharging constraint, renewable energy abandonment constraint and demand response load constraint;
the power flow constraint of the power distribution network comprises:
wherein i, j, h and k are power distribution network node numbers; deltajThe method comprises the steps that a line set with a jth power distribution network node as a head end is formed; pijThe network node is a line set taking the jth power distribution network node as a tail end; omegaPBThe method comprises the steps of (1) collecting power grid nodes; omegaSVCIs a reactive compensator set; pij,t,Qij,tRespectively the active and reactive power of line ij; x is the number ofijIs the reactance value of line ij;the active load and the reactive load of the j power distribution network node are respectively required;the reactive power of the static reactive compensator;the square of the voltage of the ith power distribution network node and the jth power distribution network node at the moment t is obtained; pjh,tRepresenting line jh active power; omegaMGRepresenting a microgrid set; omegaTRRepresenting a set of transformer nodes;Qjk,trepresents the reactive power of line jk;
the power distribution network safety constraint comprises:
wherein the content of the first and second substances,is the upper square limit of the line current;the square upper and lower limits of the node voltage are defined;
the static var compensator constraints include:
wherein the content of the first and second substances,and the upper and lower limit of reactive power output of the static reactive compensator is arranged for the node j of the power distribution network.
The gas turbine output constraints include:
wherein, RUg,RDgThe maximum upward and downward climbing rates of the gas turbine unit;respectively representing the upper limit and the lower limit of the output active power of the gas turbine unit;
the microgrid power balance constraint comprises:
wherein the content of the first and second substances,outputting uncertain variables for renewable energy sources;is the load of the kth microgrid;
the energy storage charge-discharge constraint comprises:
Ek,0=Ek,T
wherein the content of the first and second substances,is [0,1 ]]Internal variableRespectively representing an energy storage charging state and an energy storage discharging state;charging power and discharging power for stored energy respectively;charging power and discharging power stored in the kth power distribution network at the moment of t-1 are respectively stored;respectively setting an upper limit and a lower limit of energy storage charging power and an upper limit and a lower limit of discharging power;respectively, charging efficiency and discharging efficiency; ek,tIs the energy storage charge capacity; kE、the energy storage charge capacity upper and lower limits; Δ t represents a scheduling period length; ek,0Representing the initial charge capacity of energy storage; ek,TRepresenting the energy storage charge capacity at the moment T;
the curtailment renewable energy constraint comprises:
the demand response load constraints include:
wherein D isj,tThe translatable load power of the j-th distribution network node in the time period t before the demand response;the translatable load power of the j distribution network node in the time period t after the demand response;respectively, the maximum and minimum power requirements of the demand response load during time t.
Optionally, step S3 includes:
s31, writing the robust scheduling problem in the day ahead into the following form:
wherein x is a day-ahead scheduling decision variable; u is a predicted value of the day-ahead output of the renewable energy; u. ofmin、umaxRespectively representing the upper limit and the lower limit of the predicted value of the day-ahead output of the renewable energy; y is a regulation decision variable such as line power and voltage; hx is the day-ahead scheduling cost; ay is the regulation and control cost; h is a day-ahead scheduling cost coefficient matrix; a is a regulation cost coefficient matrix; A. b is a day-ahead scheduling constraint condition correlation coefficient matrix; C. d, E, G, G and f are regulation constraint cost correlation coefficient matrixes;
s32, dividing the robust scheduling problem in the day ahead into a main problem and a sub problem;
the mathematical model of the main problem is as follows:
wherein f isMPIs a main problem expression; n represents the maximum iteration number of the column constraint generation algorithm; m represents the iteration number of the column constraint generation algorithm; u. ofmThe predicted value of the day-ahead output of the renewable energy source under the worst scene of the mth iteration is obtained; y ismA regulation decision variable in the worst scene of the mth iteration; eta is the maximum regulation and control cost of the main problem in the worst scene;
the mathematical model of the subproblem is:
wherein f isSPIs a subproblem expression;and the solution result of the day-ahead scheduling decision variable of the main problem in the mth iteration is obtained.
Optionally, the step of obtaining the optimal day-ahead scheduling scheme of the power distribution network and the multi-microgrid system in the severe scene through iterative solution includes:
s34, setting the lower bound LBInfinity, upper bound UBThe column constraint generation algorithm iterates for a number m of 1.
S35, solving the main problem to obtain the best solution of the day-ahead scheduling decisionDay-ahead scheduling costAnd maximum regulatory cost in the worst scenario of major problemsAnd update the lower bound
S36, fixing scheduling decision variables before daySolving the subproblems; carrying out duality on the subproblems by adopting a Lagrangian duality method to obtain the duality problem of the subproblems; solving the dual problem to obtain a renewable energy day-ahead output value u under the worst scene in the mth iterationmAnd update the upper boundFor the dual problem, proceed to S37;
s37, if UB-LBLess than epsilon, obtaining the optimal solution of the day-ahead scheduling decisionFinishing the iteration; if U isB-LBEntering S38 when the value is more than or equal to epsilon;
s38, updating the renewable energy output predicted value u under the worst scene of main problemsmAnd adding the constraint conditions of the regulation and control phase model of the current worst scene to the main problem, wherein m is m +1, and returning to the step S35.
Optionally, step S4 includes:
s41, setting the day initial scheduling time t to be 1;
s42, obtaining t + 1-t + t based on intraday rolling optimization algorithminPredicted value of renewable energy output within day of time, where tinA step size optimized for rolling in days;
s43, on the basis of the day-ahead scheduling decision, based on the objective function and constraint conditions of the rolling optimization algorithm in day, optimizing and solving t + 1-t + tinScheduling control variables in the day of the moment, and performing real-time scheduling on the power distribution network and the multi-microgrid system in the day based on the scheduling control variables in the day of the t +1 moment; let t be t +1, repeat steps S42, S43.
Optionally, step S42 includes:
s421, according to the upper limit and the lower limit of the output predicted value of the renewable energy sources day ahead, dividing the output predicted value of the renewable energy sources into a first interval to an nth interval at equal intervals, and respectively corresponding to the discretized n states S1~Sn;
S422, establishing a one-step state transition matrix pi (t, t +1) based on the Markov chain:
where t denotes the current time, Pa,bRepresents the slave state SaTransition to State SbThe probability of (a) of (b) being,a,b∈[1,n];
s423 according to the currenttThe output predicted value of the renewable energy source is obtained at the moment to obtain the corresponding state Si,i∈[1,n];
Finding and obtaining the maximum probability P of the ith row in the one-step state transition matrixij(ii) a Then at the present timetTime state SiIn the case of (1), the renewable energy output at the next time is at the maximum probability PijTransition to State Sj(ii) a Taking the average value of the corresponding j interval as a predicted value of the output of the renewable energy source in the day at the time t + 1;
s424, let t be t +1, and repeat step S423 until t + t is obtained, while continuing to scroll the time domaininThe output prediction value of the renewable energy within the time and day; wherein t isinStep size optimized for intra-day scrolling.
Compared with the prior art, the invention has the beneficial effects that:
according to the multi-time-scale scheduling method considering large-scale renewable energy access, day-ahead scheduling and day-in scheduling can be coordinated, the influence of renewable energy uncertainty on the scheduling of the power distribution network and the multi-microgrid system is reduced, and compared with a single day-ahead scheduling method, the scheduling accuracy is improved, so that the capability of the power distribution network and the multi-microgrid system for dealing with the renewable energy uncertainty can be effectively improved.
According to the method, a two-stage robust scheduling model with multiple time scales (including a day-ahead scale and a day-inside scale) is established, so that scientific scheduling basis is provided for scheduling personnel of the power distribution network and the multi-microgrid system, and multi-time scale coordinated scheduling of the power distribution network and the multi-microgrid system is realized.
Drawings
In order to more clearly illustrate the technical solution of the present invention, the drawings used in the description will be briefly introduced, and it is obvious that the drawings in the following description are an embodiment of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts according to the drawings:
fig. 1 is a multi-time scale scheduling framework of a power distribution network and a multi-microgrid system;
FIG. 2 is a flow chart of a multi-time scale scheduling method of the present invention;
fig. 3 is a flowchart of a power distribution network and a multi-microgrid system day-ahead robust scheduling solution;
fig. 4 is a flowchart of the intraday rolling scheduling solving process of the power distribution network and the multi-microgrid system.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The multi-time scale scheduling method firstly establishes a multi-time scale scheduling framework, and divides the scheduling of the power distribution network and the multi-microgrid system into 2 stages in the day and the day, as shown in fig. 1, the method specifically comprises the following steps:
stage 1: and (5) scheduling day by day. In the day-ahead scheduling, the power distribution network and the multi-microgrid system predict the output of renewable energy sources within 24 hours in the future. And arranging a system day-ahead scheduling plan by the system scheduling personnel according to the day-ahead prediction information. In this stage, the prediction information includes not only the predicted value of the renewable energy output in the next 24 hours, but also the upper and lower prediction limits thereof. And considering that the prediction error in the day ahead is larger, constructing an uncertain set of renewable energy output by adopting robust optimization, and establishing a day ahead stage model of the power distribution network and the multi-microgrid system. In order to meet the real-time power balance of the system, the day-ahead scheduling decision at the stage only comprises a scheduling strategy which needs to be made one day ahead of time, such as a gas turbine day-ahead starting and stopping plan, a power distribution network day-ahead electricity purchasing plan, power transmission of a power distribution network and a multi-microgrid day-ahead connecting line and the like.
Stage 2: and (5) short-term scheduling in the day. Due to the large prediction range and the low prediction accuracy, the renewable energy output prediction result of one day ahead of time cannot meet the requirement of power balance. In order to accurately reflect the fluctuation of the output of the renewable energy sources and reduce the deviation between the advance scheduling and the real-time scheduling, the short-term scheduling in the day is introduced. In the scheduling in the day, ultra-short-term prediction is carried out through a regulation and control stage model, and a predicted value of the output of the renewable energy in a plurality of time periods in the future is obtained. The dispatching center can carry out economic dispatching on the output of each controllable unit on the basis of day-ahead dispatching and make an output plan of each unit in the next time period. This stage is typically completed 15 minutes to 1 hour in advance and the intra-day schedule plan is revised in a rolling fashion based on the update of the ultra-short term predictions, and is therefore a rolling schedule.
The invention provides a multi-time scale scheduling method considering large-scale renewable energy access, which is suitable for a power distribution network and a multi-microgrid system, and as shown in figure 2, the method comprises the following steps:
s1, forecasting the day-ahead output upper and lower limits of the renewable energy through the probability distribution of the day-ahead forecasting error of the renewable energy, and constructing a robust uncertain set;
step S1 includes:
s11, orderThe maximum positive and negative prediction error of the output of the nth renewable energy source set,predicting an error of the output of the nth renewable energy unit before the day; according toRespectively obtaining the lambda quantile and the 1-lambda quantile of the cumulative probability density functionWherein lambda is a preset value; the lambda can be selected according to the scheduling requirement of the system, and the smaller the lambda is, the higher the scheduling robustness is;
taking a wind and light unit as an example, the output prediction error of the wind and light unit meets the three-order mixed Gaussian distribution, namely the probability density function form of the maximum output prediction error of the wind turbine and the photovoltaic is as follows:
wherein x is a prediction error value; mu, delta and alpha are respectively expectation, standard deviation and weight phasor of Gaussian distribution of each group, and alpha isiThe weight of the ith group of Gaussian distribution of the mixed Gaussian distribution; mu.si(ii) an expectation of an ith set of Gaussian distributions for the mixed Gaussian distributions; deltaiThe standard deviation of the ith set of gaussian distributions of the hybrid gaussian distribution. i is 1,2, 3.
S12, representing the uncertainty of the renewable energy contribution as:
whereinThe actual output of the nth renewable energy source unit is obtained;predicting output for the nth renewable energy unit in the day ahead;
S2, constructing a two-stage robust scheduling model of the power distribution network and the multi-microgrid system; the two-stage robust scheduling model comprises a day-ahead stage model and a regulation and control stage model; the day-ahead stage model makes a day-ahead scheduling decision based on the output of renewable energy predicted day-ahead; and the regulation and control stage model identifies the worst scene of the output of the renewable energy sources based on the day-ahead scheduling decision, and corrects the day-ahead scheduling decision aiming at the worst scene.
The worst scheduling scene refers to a renewable energy uncertain variable value scene which enables the scheduling cost of the system to be the maximum under the current determined day-ahead scheduling decision. According to the convex optimization theory, the worst scene is generally a scene in which the output of the renewable energy takes an extreme value at a certain vertex of a polyhedron solution space.
The day-ahead scale scheduling is divided into a day-ahead stage (based on a day-ahead stage model) and a regulation and control stage (based on a regulation and control stage model), and an objective function of the two-stage robust scheduling model mainly comprises the day-ahead scheduling cost and the regulation and control cost of the power distribution network and the multiple micro-grids.
The objective function of the day-ahead stage model mainly comprises day-ahead scheduling cost and regulation and control cost of the power distribution network and the multiple micro-grids. The objective function of the day-ahead phase model is:
wherein i and j represent the node number of the power distribution network; t is the total scheduling time interval; t represents the current scheduling time; ij is a power distribution network line between the ith power distribution network node and the jth power distribution network node; f. ofda1Scheduling cost for the power distribution network and the multi-microgrid system day ahead; f. ofda2Cost is regulated and controlled for the power distribution network and the multi-microgrid system; x is a day-ahead scheduling decision variable; y is a regulation decision variable; xi is an uncertain variable; k is the number of the micro-grid; n is a radical ofMGThe number of the micro-grids; ctr、Closs、CIDRRespectively obtaining unit electricity purchasing cost, distribution network loss cost and distribution network node load demand response cost of the slave main network of the distribution network; cre、CesRespectively abandon for the microgridA penalty coefficient of renewable energy resources and a penalty coefficient of energy storage loss cost;purchasing power from a main network for the power distribution network;the output of a gas turbine in the kth micro-grid is obtained; i isk,tIs [0,1 ]]The internal variable represents the output state variable of the gas turbine unit in the kth micro-grid; dj,tThe translatable load power of the j distribution network node at the scheduling time t before the demand response;the translatable load power of the j distribution network node at the scheduling time t after the demand response;the renewable energy power is abandoned for the kth micro-grid;the square of the line current of the power distribution network; r isijIs a line resistance; omegaPE、ΩTRRespectively a power distribution network line set and a power distribution network transformer node set;charging power and discharging power for stored energy respectively; a isk、bk、ckRespectively, gas turbine output cost coefficients;
the constraints of the day-ahead phase model include: a main grid output constraint, a gas turbine minimum start/shut down time constraint, a tie line power transmission constraint;
the primary grid output force constraints include:
whereinTransmitting reactive power for the main network;respectively transmitting upper and lower limits of reactive power for the main network;and transmitting upper and lower limits of active power for the main network.
The gas turbine minimum on/off time constraints include:
wherein the content of the first and second substances,the minimum starting time and the minimum closing time of the unit.
The tie-line power transfer constraints include
Wherein,Transmitting power to the kth micro-grid for the power distribution network;respectively the lower limit and the upper limit of the transmission power between the micro-grid and the distribution network.
The objective function of the regulation phase model is: under the determined day-ahead scheduling decision, the regulation and control cost f of the power distribution network and the multi-microgrid system under the worst renewable energy output scene is realizedda2And minimum.
The constraint conditions of the regulation phase model comprise: the method comprises the following steps of power distribution network power flow constraint, power distribution network safety constraint, static reactive compensator constraint, gas turbine output constraint, micro-grid power balance constraint, energy storage charging and discharging constraint, renewable energy abandonment constraint and demand response load constraint;
the power flow constraint of the power distribution network comprises:
wherein the content of the first and second substances,ij, h and k are the numbers of the nodes of the power distribution network; deltajThe method comprises the steps that a line set with a jth power distribution network node as a head end is formed; pijThe network node is a line set taking the jth power distribution network node as a tail end; omegaPBThe method comprises the steps of (1) collecting power grid nodes; omegaSVCIs a reactive compensator set; pij,t,Qij,tRespectively the active and reactive power of line ij; x is the number ofijIs the reactance value of line ij;the active load and the reactive load of the j power distribution network node are respectively required;the reactive power of the static reactive compensator;the square of the voltage of the ith power distribution network node and the jth power distribution network node at the moment t is obtained; pjh,tRepresenting line jh active power; omegaMGRepresenting a microgrid set; omegaTRRepresenting a set of transformer nodes; qjk,tRepresents the reactive power of line jk;
the power distribution network safety constraint comprises:
wherein the content of the first and second substances,is the upper square limit of the line current;the square upper and lower limits of the node voltage are defined;
the static var compensator constraints include:
wherein the content of the first and second substances,and the upper and lower limit of reactive power output of the static reactive compensator is arranged for the node j of the power distribution network.
The gas turbine output constraints include:
wherein, RUg,RDgThe maximum upward and downward climbing rates of the gas turbine unit;respectively representing the upper limit and the lower limit of the output active power of the gas turbine unit;
the microgrid power balance constraint comprises:
wherein the content of the first and second substances,outputting uncertain variables for renewable energy sources;is the load of the kth microgrid;
the energy storage charge-discharge constraint comprises:
Ek,0=Ek,T
wherein the content of the first and second substances,is [0,1 ]]The internal variables respectively represent the energy storage charging state and the discharging state; charging power and discharging power for stored energy respectively;charging power and discharging power stored in the kth power distribution network at the moment of t-1 are respectively stored;respectively setting an upper limit and a lower limit of energy storage charging power and an upper limit and a lower limit of discharging power;respectively, charging efficiency and discharging efficiency; ek,tIs the energy storage charge capacity; kE、the energy storage charge capacity upper and lower limits; Δ t represents a scheduling period length; ek,0Representing the initial charge capacity of energy storage;Ek,Trepresenting the energy storage charge capacity at the moment T;
the curtailment renewable energy constraint comprises:
the demand response load constraints include:
wherein D isj,tThe translatable load power of the j-th distribution network node in the time period t before the demand response;the translatable load power of the j distribution network node in the time period t after the demand response;respectively, the maximum and minimum power requirements of the demand response load during time t.
S3: splitting a day-ahead robust scheduling problem into main and sub problems through a column-and-constraint generation (C & CG) algorithm, and iteratively solving to obtain an optimal day-ahead scheduling decision of the power distribution network and the multi-microgrid system in the worst scene; the method comprises the steps that a main problem is solved to obtain an optimal day-ahead scheduling scheme in the worst scene, the optimal day-ahead scheduling scheme is transmitted to sub-problems, the sub-problems are solved through a dual principle, the regulation and control cost in the current worst scene and the output of renewable energy in the worst scene are obtained through solving, the worst scene in the day-ahead scheduling scheme is identified, the main problem decision is influenced by adding the regulation and control stage constraint in the worst scene, and finally the optimal solution of the day-ahead robust scheduling problem is obtained through iteration of the main and sub-problems. The main problem objective function comprises the day-ahead scheduling cost and the regulation and control cost under the worst scene, and is the same as the day-ahead scheduling model, but the constraint conditions of the main problem not only comprise the constraint conditions of the day-ahead stage model, but also comprise the constraint conditions of the m worst-scene regulation and control stage models generated in iteration.
The subproblem objective function is the regulation cost and is the same as the objective function of the regulation stage model; the constraint of the sub-problem is the constraint of a regulation and control stage model, and the regulation and control cost under the worst scene under the day-ahead decision of the current main problem is obtained through dual solution.
Step S3 includes:
s31, writing the robust scheduling problem in the day ahead into the following form based on the objective function and the constraint condition of the day ahead stage model:
wherein x is a day-ahead scheduling decision variable; u is a predicted value of the day-ahead output of the renewable energy; u. ofmin、umaxRespectively representing the upper limit and the lower limit of the predicted value of the day-ahead output of the renewable energy; y is a regulation decision variable such as line power and voltage; hx is the day-ahead scheduling cost; ay is the regulation and control cost; h is a day-ahead scheduling cost coefficient matrix; a is a regulation cost coefficient matrix; A. b is a day-ahead scheduling constraint condition correlation coefficient matrix; C. d, E, G, G and f are regulation constraint cost correlation coefficient matrixes;
s32, dividing the robust scheduling problem in the day ahead into a main problem and a sub problem;
the mathematical model of the main problem is as follows:
wherein f isMPIs a main problem expression; n represents the maximum iteration number of the column constraint generation algorithm; m represents the iteration number of the column constraint generation algorithm; u. ofmThe day-ahead output of renewable energy sources in the worst scene of the mth iteration is predictedMeasuring; y ismA regulation decision variable in the worst scene of the mth iteration; eta is the maximum regulation and control cost of the main problem in the worst scene;
the mathematical model of the subproblem is:
wherein f isSPIs a subproblem expression;and the solution result of the day-ahead scheduling decision variable of the main problem in the mth iteration is obtained.
As shown in fig. 3, the iterative solution to obtain the optimal day-ahead scheduling scheme of the power distribution network and the multi-microgrid system in the severe scene includes the steps of:
s34, setting the lower bound LBInfinity, upper bound UBThe column constraint generation algorithm iterates for a number m of 1.
S35, solving the main problem to obtain the best solution of the day-ahead scheduling decisionDay-ahead scheduling costAnd maximum regulatory cost in the worst scenario of major problemsAnd update the lower bound
S36, fixing scheduling decision variables before daySolving the subproblems; carrying out duality on the subproblems by adopting a Lagrangian duality method to obtain the duality problem of the subproblems; solving the dual problem if a feasible solution existsAnd obtaining the predicted value u of the day-ahead output of the renewable energy source under the worst scene in the mth iterationmAnd update the upper boundFor the dual problem, proceed to S37; if no feasible solution exists in the dual problem, a renewable energy day-ahead output predicted value u under the worst scene in the mth iteration is obtainedmGo to S38;
in this embodiment, the expression of the dual problem of the sub-problem is:
CTπ1+DTπ2+ETπ3≤a
π1≤0
umin≤u≤umax
wherein, pi1、π3、π2Is the dual variable introduced. According to the dual principle, the dual problem is the same as the original problem solving result, so that the sub-problem is solved by directly solving the dual problem. The subproblems can be solved through a dual algorithm, the regulation and control cost under the current worst scene and the renewable energy output under the worst scene are obtained through solving, and the identification of the worst scene is realized by obtaining the renewable energy output under the worst scene.
S37, if UB-LBLess than epsilon, obtaining the optimal solution of the day-ahead scheduling decisionFinishing the iteration; if U isB-LBEntering S38 when the value is more than or equal to epsilon;
s38, updating the renewable energy output predicted value u under the worst scene of main problemsmAnd adding the constraint of the regulation and control phase model of the current worst scene to the main problem, wherein m is m +1, and returning to the step S35.
S4: on the basis of the optimal day-ahead scheduling decision, a day-in rolling optimization algorithm is adopted to perform rolling optimization on day-in scheduling of the power distribution network and the multi-microgrid system, so that a day-in rolling decision of the power distribution network and the multi-microgrid system is obtained (in the embodiment, the day-in rolling decision is used for scheduling for 15 minutes to 1 hour in the future), and multi-time scale scheduling of the power distribution network and the multi-microgrid system is realized.
It is considered that the accuracy of prediction of renewable energy output decreases as the prediction time scale increases. The two-stage robust scheduling model based on the day-ahead prediction result is difficult to meet the requirement of real-time scheduling, so that the adjustment needs to be carried out on the basis of day-ahead scheduling decisions by adopting an intra-day rolling optimization algorithm.
And the day-by-day rolling optimization algorithm follows the day-by-day energy storage charging and discharging state, the unit starting and stopping plan and the tie line power obtained in the step S3, and the day-by-day decision variables such as the unit output and the like are adjusted according to the short-term prediction of the day-by-day renewable energy fluctuation.
Objective function f of rolling optimization algorithm in daydiComprises the following steps:
wherein, tinA step size optimized for rolling in days; PF is an energy storage penalty item; pf is a penalty coefficient;the energy storage charge capacity obtained by day-ahead scheduling.
The constraint conditions of the rolling optimization algorithm in the day are the same as those of the model in the regulation and control stage.
As shown in fig. 4, step S4 includes:
s41, setting the day initial scheduling time t to be 1;
s42, obtaining t + 1-t + t based on intraday rolling optimization algorithminDay of the dayInternal renewable energy output prediction value, where tinA step size optimized for rolling in days;
s43, on the basis of the day-ahead scheduling decision, based on the objective function and constraint conditions of the rolling optimization algorithm in day, optimizing and solving t + 1-t + tinScheduling control variables in the day of the moment, and performing real-time scheduling on the power distribution network and the multi-microgrid system in the day based on the scheduling control variables in the day of the t +1 moment; let t be t +1, repeat steps S42, S43.
Step S42 includes:
s421, according to the upper limit and the lower limit of the output predicted value of the renewable energy sources day ahead, dividing the output predicted value of the renewable energy sources into a first interval to an nth interval at equal intervals, and respectively corresponding to the discretized n states S1~Sn;
S422, establishing a one-step state transition matrix pi (t, t +1) based on the Markov chain:
where t denotes the current time, Pa,bRepresents the slave state SaTransition to State SbProbability of, a, b ∈ [1, n ]];
S423 according to the currenttThe output predicted value of the renewable energy source is obtained at the moment to obtain the corresponding state Si,i∈[1,n];
Finding and obtaining the maximum probability P of the ith row in the one-step state transition matrixij(ii) a Then at the present timetTime state SiIn the case of (1), the renewable energy output at the next time is at the maximum probability PijTransition to State Sj(ii) a Taking the average value of the corresponding j interval as a predicted value of the output of the renewable energy source in the day at the time t + 1;
s424, let t be t +1, and repeat step S423 until t + t is obtained, while continuing to scroll the time domaininThe output prediction value of the renewable energy within the time and day; wherein t isinStep size optimized for intra-day scrolling.
According to the multi-time-scale scheduling method considering large-scale renewable energy access, day-ahead scheduling and day-in scheduling can be coordinated, the influence of renewable energy uncertainty on the scheduling of the power distribution network and the multi-microgrid system is reduced, and compared with a single day-ahead scheduling method, the scheduling accuracy is improved, so that the capability of the power distribution network and the multi-microgrid system for dealing with the renewable energy uncertainty can be effectively improved.
According to the method, a two-stage robust scheduling model with multiple time scales (including a day-ahead scale and a day-inside scale) is established, so that scientific scheduling basis is provided for scheduling personnel of the power distribution network and the multi-microgrid system, and multi-time scale coordinated scheduling of the power distribution network and the multi-microgrid system is realized.
While the invention has been described with reference to specific embodiments, the invention is not limited thereto, and various equivalent modifications and substitutions can be easily made by those skilled in the art within the technical scope of the invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A multi-time scale scheduling method considering large-scale renewable energy access is suitable for a power distribution network and a multi-microgrid system, and is characterized by comprising the following steps:
s1, forecasting the day-ahead output upper and lower limits of the renewable energy through the probability distribution of the day-ahead forecasting error of the renewable energy, and constructing a robust uncertain set;
s2, constructing a two-stage robust scheduling model of the power distribution network and the multi-microgrid system; the two-stage robust scheduling model comprises a day-ahead stage model and a regulation and control stage model; the day-ahead stage model makes a day-ahead scheduling decision based on the predicted day-ahead output of the renewable energy; the regulation and control stage model is based on the day-ahead scheduling decision, and the regulation and control cost under the current worst scene and the output of the renewable energy under the worst scene are obtained by solving the regulation and control stage model, so that the worst scene of the output of the renewable energy is identified, and the day-ahead scheduling decision is corrected aiming at the worst scene;
s3: splitting a day-ahead robust scheduling problem into main and sub problems through a column constraint generation algorithm, and iteratively solving to obtain an optimal day-ahead scheduling decision of the power distribution network and the multi-microgrid system in the worst scene;
and S4, performing rolling optimization on the day-to-day scheduling of the power distribution network and the multi-microgrid system by adopting a day-to-day rolling optimization algorithm on the basis of the optimal day-to-day scheduling decision, and realizing multi-time scale scheduling of the power distribution network and the multi-microgrid system.
2. The method for multi-time-scale scheduling considering large-scale renewable energy access according to claim 1, wherein step S1 comprises:
s11, orderThe maximum positive and negative prediction error of the output of the nth renewable energy source set,predicting an error of the output of the nth renewable energy unit before the day; according toRespectively obtaining the lambda quantile and the 1-lambda quantile of the cumulative probability density functionWherein lambda is a preset value;
s12, representing the uncertainty of the renewable energy contribution as:
whereinThe actual output of the nth renewable energy source unit is obtained;predicting output for the nth renewable energy unit in the day ahead;
3. The multi-time scale scheduling method considering large-scale renewable energy access of claim 2, wherein the objective function of the stage-of-day model is:
wherein i and j represent the node number of the power distribution network; t is the total scheduling time interval; t represents the current scheduling time; ij is a power distribution network line between the ith power distribution network node and the jth power distribution network node; f. ofda1Scheduling cost for the power distribution network and the multi-microgrid system day ahead; f. ofda2Cost is regulated and controlled for the power distribution network and the multi-microgrid system; x is a day-ahead scheduling decision variable; y is a regulation decision variable; xi is an uncertain variable; k is the number of the micro-grid; n is a radical ofMGThe number of the micro-grids; ctr、Closs、CIDRThe unit electricity purchasing cost and the distribution network loss of the main network are respectively selected for the distribution networkCost and distribution network node load demand response cost; cre、CesRespectively discarding a punishment coefficient of renewable energy resources and a punishment coefficient of energy storage loss cost for the micro-grid;purchasing power from a main network for the power distribution network;the output of a gas turbine in the kth micro-grid is obtained; i isk,tIs [0,1 ]]The internal variable represents the output state variable of the gas turbine unit in the kth micro-grid; dj,tThe translatable load power of the j distribution network node at the scheduling time t before the demand response;the translatable load power of the j distribution network node at the scheduling time t after the demand response;the renewable energy power is abandoned for the kth micro-grid;the square of the line current of the power distribution network; r isijIs a line resistance; omegaPE、ΩTRRespectively a power distribution network line set and a power distribution network transformer node set;charging power and discharging power for stored energy respectively; a isk、bk、ckRespectively, gas turbine output cost coefficients;
the objective function of the regulation phase model is: under the determined day-ahead scheduling decision, the regulation and control cost f of the power distribution network and the multi-microgrid system under the worst renewable energy output scene is realizedda2And minimum.
4. The method of claim 3, wherein the constraints of the pre-day phase model include: a main grid output constraint, a gas turbine minimum start/shut down time constraint, a tie line power transmission constraint;
the primary grid output force constraints include:
whereinTransmitting reactive power for the main network;respectively transmitting upper and lower limits of reactive power for the main network;transmitting upper and lower limits of active power for the main network;
the gas turbine minimum on/off time constraints include:
wherein the content of the first and second substances,the minimum starting time and the minimum closing time of the unit are obtained;
the tie-line power transfer constraints include
5. The method of multi-time scale scheduling with consideration of large-scale renewable energy access of claim 4, wherein an objective function f of a rolling-in-the-day optimization algorithmdiComprises the following steps:
6. The multi-time scale scheduling method considering large-scale renewable energy access according to claim 5, wherein the constraint condition of the rolling optimization algorithm in the day is the same as the constraint condition of the regulation phase model, and comprises: the method comprises the following steps of power distribution network power flow constraint, power distribution network safety constraint, static reactive compensator constraint, gas turbine output constraint, micro-grid power balance constraint, energy storage charging and discharging constraint, renewable energy abandonment constraint and demand response load constraint;
the power flow constraint of the power distribution network comprises:
wherein i, j, h and k are power distribution network node numbers; deltajThe method comprises the steps that a line set with a jth power distribution network node as a head end is formed; pijThe network node is a line set taking the jth power distribution network node as a tail end; omegaPBThe method comprises the steps of (1) collecting power grid nodes; omegaSVCIs a reactive compensator set; pij,t,Qij,tRespectively the active and reactive power of line ij; x is the number ofijIs the reactance value of line ij;the active load and the reactive load of the j power distribution network node are respectively required;the reactive power of the static reactive compensator;the square of the voltage of the ith power distribution network node and the jth power distribution network node at the moment t is obtained; pjh,tRepresenting line jh active power; omegaMGRepresenting a microgrid set; omegaTRRepresenting a set of transformer nodes; qjk,tRepresents the reactive power of line jk;
the power distribution network safety constraint comprises:
wherein the content of the first and second substances,is the upper square limit of the line current;the square upper and lower limits of the node voltage are defined;
the static var compensator constraints include:
wherein the content of the first and second substances,static var compensator for power distribution network node j installationThe reactive power output upper and lower limits of the compensator;
the gas turbine output constraints include:
wherein, RUg,RDgThe maximum upward and downward climbing rates of the gas turbine unit;respectively representing the upper limit and the lower limit of the output active power of the gas turbine unit;
the microgrid power balance constraint comprises:
wherein the content of the first and second substances,outputting uncertain variables for renewable energy sources;is the load of the kth microgrid;
the energy storage charge-discharge constraint comprises:
Ek,0=Ek,T
wherein the content of the first and second substances,is [0,1 ]]The internal variables respectively represent the energy storage charging state and the discharging state;charging power and discharging power for stored energy respectively;charging power and discharging power stored in the kth power distribution network at the moment of t-1 are respectively stored;respectively setting an upper limit and a lower limit of energy storage charging power and an upper limit and a lower limit of discharging power;respectively, charging efficiency and discharging efficiency; ek,tIs the energy storage charge capacity;the energy storage charge capacity upper and lower limits; Δ t represents a scheduling period length; ek,0Representing the initial charge capacity of energy storage; ek,TRepresents time T storeAn energy-to-charge capacity;
the curtailment renewable energy constraint comprises:
the demand response load constraints include:
wherein D isj,tThe translatable load power of the j-th distribution network node in the time period t before the demand response;the translatable load power of the j distribution network node in the time period t after the demand response;respectively, the maximum and minimum power requirements of the demand response load during time t.
7. The method for multi-time-scale scheduling considering large-scale renewable energy access according to claim 6, wherein step S3 comprises:
s31, writing the robust scheduling problem in the day ahead into the following form based on the objective function and the constraint condition of the day ahead stage model:
wherein x is a day-ahead scheduling decision variable; u is renewable energy day-ahead outputMeasuring; u. ofmin、umaxRespectively representing the upper limit and the lower limit of the predicted value of the day-ahead output of the renewable energy; y is a regulation decision variable such as line power and voltage; hx is the day-ahead scheduling cost; ay is the regulation and control cost; h is a day-ahead scheduling cost coefficient matrix; a is a regulation cost coefficient matrix; A. b is a day-ahead scheduling constraint condition correlation coefficient matrix; C. d, E, G, G and f are regulation constraint cost correlation coefficient matrixes;
s32, dividing the robust scheduling problem in the day ahead into a main problem and a sub problem;
the mathematical model of the main problem is as follows:
wherein f isMPIs a main problem expression; n represents the maximum iteration number of the column constraint generation algorithm; m represents the iteration number of the column constraint generation algorithm; u. ofmThe predicted value of the day-ahead output of the renewable energy source under the worst scene of the mth iteration is obtained; y ismA regulation decision variable in the worst scene of the mth iteration; eta is the maximum regulation and control cost of the main problem in the worst scene;
the mathematical model of the subproblem is:
8. The multi-time-scale scheduling method considering large-scale renewable energy access of claim 7, wherein the step of iteratively solving in step S3 to obtain the optimal day-ahead scheduling scheme of the power distribution network and the multi-microgrid system in the severe scene comprises the steps of:
s34, setting the lower bound LBInfinity, upper bound UB1, defining the iteration number m of the column constraint generation algorithm as 1;
s35, solving the main problem to obtain the best solution of the day-ahead scheduling decisionDay-ahead scheduling costAnd maximum regulatory cost in the worst scenario of major problemsAnd update the lower bound
S36, fixing scheduling decision variables before daySolving the subproblems; carrying out duality on the subproblems by adopting a Lagrangian duality method to obtain the duality problem of the subproblems; solving the dual problem to obtain a renewable energy day-ahead output value u under the worst scene in the mth iterationmAnd update the upper bound For the dual problem, proceed to S37;
s37, if UB-LBLess than epsilon, obtaining the optimal solution of the day-ahead scheduling decisionFinishing the iteration; if U isB-LBEntering S38 when the value is more than or equal to epsilon;
s38, updating the main questionRenewable energy output predicted value u in worst scenemAnd adding a regulation and control stage model constraint condition in the current worst scene to the main problem, wherein m is m +1, and returning to the step S35.
9. The method according to claim 8, wherein the step S4 comprises:
s41, setting the day initial scheduling time t to be 1;
s42, obtaining t + 1-t + t based on intraday rolling optimization algorithminPredicted value of renewable energy output within day of time, where tinA step size optimized for rolling in days;
s43, on the basis of the day-ahead scheduling decision, based on the objective function and constraint conditions of the rolling optimization algorithm in day, optimizing and solving t + 1-t + tinScheduling control variables in the day of the moment, and performing real-time scheduling on the power distribution network and the multi-microgrid system in the day based on the scheduling control variables in the day of the t +1 moment; let t be t +1, repeat steps S42, S43.
10. The method for multi-time-scale scheduling considering large-scale renewable energy access of claim 9, wherein step S42 comprises:
s421, according to the upper limit and the lower limit of the output predicted value of the renewable energy sources day ahead, dividing the output predicted value of the renewable energy sources into a first interval to an nth interval at equal intervals, and respectively corresponding to the discretized n states S1~Sn;
S422, establishing a one-step state transition matrix pi (t, t +1) based on the Markov chain:
where t denotes the current time, Pa,bRepresents the slave state SaTransition to State SbProbability of, a, b ∈ [1, n ]];
S423, obtaining pairs according to the output predicted value of the renewable energy at the current t momentCorresponding state Si,i∈[1,n];
Finding and obtaining the maximum probability P of the ith row in the one-step state transition matrixij(ii) a Then state S at the current time tiIn the case of (1), the renewable energy output at the next time is at the maximum probability PijTransition to State Sj(ii) a Taking the average value of the corresponding j interval as a predicted value of the output of the renewable energy source in the day at the time t + 1;
s424, let t be t +1, and repeat step S423 until t + t is obtained, while continuing to scroll the time domaininThe output prediction value of the renewable energy within the time and day; wherein t isinStep size optimized for intra-day scrolling.
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