CN114139780A - Coordinated optimization method and system for virtual power plant and power distribution network containing distributed power supply - Google Patents
Coordinated optimization method and system for virtual power plant and power distribution network containing distributed power supply Download PDFInfo
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Abstract
The invention discloses a coordinated optimization method and a coordinated optimization system for a virtual power plant and a power distribution network containing distributed power supplies, wherein the coordinated optimization method comprises the following steps: acquiring network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of a power distribution network accessed by a current virtual power plant; inputting the power distribution network VPP distribution robust coordination optimization model to a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain the daily transaction electric quantity and the operation cost of the power distribution network; the two stages comprise a first stage model and a second stage model, wherein the first stage model is used for constraining the operation domain of each period of the equipment in the VPP to obtain the integral output of each period of the VPP; and the second-stage model is used for performing power distribution network optimal scheduling by using the result of the first-stage model, and solving to obtain the daily transaction electric quantity and the operation cost of the power distribution network. The advantages are that: the consumption level of renewable energy sources is improved, and the economical efficiency of the system is optimized; the power distribution network electricity purchasing cost can be reduced, the electricity selling income is improved, and peak clipping and valley filling can be realized.
Description
Technical Field
The invention relates to a coordinated optimization method and system for a virtual power plant and a power distribution network containing distributed power supplies, and belongs to the technical field of distributed power supply control.
Background
In order to realize the national aims of 'carbon peak reaching and carbon neutralization', a distributed power supply which takes renewable energy as power supply is connected to a power distribution network in a high proportion. In recent years, virtual power plants have been rapidly developed as an effective means for consuming renewable energy, but at the same time, the uncertainty of distributed power supplies also brings great challenges to the operation control of the virtual power plants. In order to cope with the increment of uncertainty caused by high-proportion renewable energy, a Virtual Power Plant (VPP) based on a distributed Power supply is generated at the same time, and the complementary cooperative operation of the VPP and the renewable energy is realized by excavating the flexibility adjusting capability of resources in each link of source network load storage.
The VPP aggregates all distributed power supplies and adjustable resources contained in a certain area through an internal communication and control architecture, and realizes effective management of large-scale and scattered distributed power supplies. The method takes a Yunnan small Zhongdian wind-solar-water distributed power supply demonstration project as a research object, and analyzes the coordination scheduling problem of a virtual power plant containing wind, solar and water and a power distribution company. The coordinated operation and reliable grid connection of a large number of distributed power supplies are realized by uniformly and optimally scheduling the combined heat and power generation units aggregated by the VPPs and the scattered small hydropower stations through an energy management system.
However, in the prior art, uncertainty is caused by processing distributed power access by using a distributed robust optimization method, and the problem needs to be solved urgently.
Disclosure of Invention
Aiming at the problem of cooperative optimization of VPP and a power distribution network, the invention provides a coordinated optimization method and a coordinated optimization system of a virtual power plant containing a distributed power supply and the power distribution network, wherein uncertainty caused by distributed power supply access is processed by adopting a distributed robust optimization method.
In order to solve the technical problem, the invention provides a coordinated optimization method of a virtual power plant containing distributed power supplies and a power distribution network, which comprises the following steps:
acquiring network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of a power distribution network accessed by a current virtual power plant;
inputting the power distribution network VPP distribution robust coordination optimization model to a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain the daily transaction electric quantity and the operation cost of the power distribution network; the two stages comprise a first stage model and a second stage model, wherein the first stage model is used for constraining the operation domain of each period of the equipment in the VPP to obtain the integral output of each period of the VPP; the second-stage model is used for carrying out power distribution network optimization scheduling by using the result of the first-stage model, and solving to obtain daily transaction electric quantity and operation cost of the power distribution network;
a VPP internal constraint stage and a power distribution network optimization scheduling stage based on the result of the VPP internal constraint stage;
the construction of the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes comprises the following steps:
constructing a two-stage power distribution network coordination optimization model containing a VPP, wherein the VPP is a virtual power plant of a distributed power supply constructed on the basis of a distributed photovoltaic power generation system, an energy storage battery, a gas turbine and a controllable load which are connected into a power distribution network; and considering the uncertainty of photovoltaic output, and constructing a multi-discrete scene-based two-stage power distribution network VPP distribution robust coordination optimization model based on the two-stage power distribution network coordination optimization model containing VPP.
Further, the two-stage power distribution network coordination optimization model containing the VPP comprises:
the first stage model, the objective function is the running cost of the VPP in the scheduling period, and is expressed as:
in the formula (I), the compound is shown in the specification,cost factors for the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively,the rates of adjustment of the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively;
the VPP running cost objective function in the scheduling period comprises the following constraints:
1) DG constraints
In the formula, Pi DG,minAnd Pi DG,maxRespectively DG output powerUpper and lower limits of (d);andrespectively representing upward and downward climbing rate limits of the DG, wherein t and t +1 respectively represent two adjacent time periods in front and back, and the formula (1-1) and the formula (1-2) respectively represent DG output constraint and climbing rate constraint;
2) ESS constraints
In the formula (I), the compound is shown in the specification,andrepresents the charge and discharge power of the ESS,andidentified by 0-1 for the charging and discharging state of the ESS,indicating that the device is in a charging state,indicating a discharging or idle state, the ESS cannot be charged and discharged simultaneously at the same time;represents the upper limit of the charging and discharging power of the ESS;andas is the charge-discharge coefficient of the ESS,andrepresenting the lower limit and the upper limit of the capacity of the ESS, and respectively representing energy storage charge-discharge power limit and energy storage electric quantity constraint by an equation (1-3) and an equation (1-4);
3) SL constraint
In the formula Pi SL,down Pi SL,upRespectively SL load removal and loadShifting into a maximum value; pi SL,maxThe maximum load translation amount;for the load non-translatable period, equations (1-5) represent a load translation power constraint, and equations (1-6) represent a load translation power balance constraint, a load translation power total constraint and a non-translatable period constraint;
4) IL constraint
In the formula (I), the compound is shown in the specification,for the power of the call for the IL,is a 0-1 variable, P, representing the calling state of ILi IL,maxAn upper limit for power per call;is IL atUpper limit of number of calls in scheduling period, TmaxAnd TminRespectively the maximum continuous calling times and the minimum continuous non-called times;for the non-callable period, equations (1-7) represent an IL call power constraint, equations (1-8) represent a call number constraint, a continuous non-call number constraint, and a non-callable period constraint;
5) PV restraint
The active power of the distributed photovoltaic is set to be in a maximum power point tracking mode, the photovoltaic is connected into the power distribution network through the inverter, and therefore the reactive power of the photovoltaic is adjustable and limited by the capacity of the inverter:
in the formula:representing the active power of the photovoltaic inverter during the period t,representing the reactive power of the photovoltaic inverter during the period t,is the maximum apparent power of the photovoltaic inverter;
and in the second stage model, the optimization target is the minimum cost in the operation period of the power distribution network, and the target function minF is as follows:
in the formula, Δ T is a time interval, and T is a scheduling period; etabuy,b、Respectively the electricity price for purchasing electricity in the day ahead and the electricity price for purchasing electricity in the spot market,selling electricity for the distribution network; b and N are the number of load nodes of the power distribution network and the number of VPPs respectively; pt B、Pt R、The method comprises the following steps of respectively purchasing electric quantity in the day ahead, purchasing electric quantity in the spot market and using electric load of a user;calling power for the VPP, obtained by a first stage model optimization:
representing the active power of the photovoltaic in the VPP at time t,representing the discharge power of the stored energy in VPP at time t,representing the heavy electric power stored in the VPP at time t,
the objective function of the second stage model contains the following constraints:
1) flow restraint
Vj,t 2=Vi,t 2-2(Pij,trij+Qij,txij)+Iij,t 2(rij 2+xij 2)
J → k represents the set of all line end nodes k pointed by the node j as the head end; r isijRepresenting the resistance, x, on branch ijijRepresents the reactance of branch ij; i isij,tRepresents the current on branch ij; vi,tRepresenting the voltage assignment at node i, Pij,tAnd Qij,tRespectively representing active power and reactive power at the head end of the branch ij;andrepresents the active and reactive injection of the jth VPP;indicating the reactive compensation quantity, P, of a continuous type reactive compensation devicejk,tI → j represents the set of all line end nodes j pointed to by node i as the head end,representing the active load, Q, of node jjk,tRepresenting the reactive power at the head end of branch jk,the PV reactive power is represented by the PV reactive power,representing reactive load of node j, Vj,tRepresents the voltage magnitude at node j;
the above equation is further relaxed as a second order cone constraint, as follows:
2) power balance constraint
In the formula Pt lossThe active loss of the network is equivalent to the sum of active power injected by all nodes;
3) voltage safety constraints
In the formula:andrespectively representing the allowable voltage V of the systemj,tUpper and lower limits;
4) reactive power compensator restraint
In the formula:andreactive compensation permitted for the reactive compensation device respectivelyA lower limit and an upper limit.
Further, the uncertainty of the photovoltaic output is considered, a two-stage power distribution network VPP distribution robust coordination optimization model based on a multi-discrete scene is constructed on the basis of the two-stage power distribution network coordination optimization model containing VPP, and the two-stage power distribution network VPP distribution robust coordination optimization model is expressed as follows:
Ax≤c (2)
Ex+Fys≤d (3)
||Mys+o||2≤qTys+n (4)
Hys≤j (5)
Gys=ξs (6)
in formula (1): x represents a first stage variable comprising:a is a cost coefficient corresponding to the output decision of different equipment; y issThe second-stage variables under the scene s comprise: vj,t,Iij,t, Pij,t,Qij,t,psIs the probability of occurrence of scene s; a, c, d, E, F, G, H, j, M, n, o and q are all vectors or coefficient matrixes corresponding to variables in the model; xisPredicting an output vector for the PV; n is a radical ofsRepresenting a limited number of discrete scenes, NsK actual scenes are obtained from the limited discrete scenes through historical data and are obtained through scene clustering method screening; equation (2) represents all constraints associated with the first stage variables; equation (3) represents the constraint associated with the first stage variable and the second stage variable; equation (4) represents a second order cone relaxation constraint; equation (5) represents the relevant constraint of the second stage variable; equation (6) represents the equality constraint of the photovoltaic power generation uncertainty predicted output.
Further, the input is performed to a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain the daily transaction electric quantity and the operation cost of the power distribution network, and the method comprises the following steps:
and solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multi-discrete scene by adopting a column and constraint generation algorithm to obtain the daily trading electric quantity and the operating cost of the power distribution network with the VPP under the uncertain environment.
Further, the method for solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes by adopting the column and constraint generation algorithm to obtain the power distribution network intra-day and VPP transaction electric quantity and the operation cost under the uncertain environment comprises the following steps:
decomposing the problem of solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes into a main problem and a sub-problem, wherein the main problem provides a lower bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the sub-problem provides an upper bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the upper bound and the lower bound are gradually closed through continuous iteration, when the difference value of the two bounds is smaller than a preset value, the iteration is stopped, an optimal solution is returned, and the power distribution network transaction power quantity and the operation cost in the day with the VPP under an uncertain environment are obtained;
the lower bound of the main question, denoted:
in the formula (I), the compound is shown in the specification,for the probability distribution found by the sub-problem,m is a second-stage variable flexibly adjusted according to the scene, and is the total number of model iterations;
the upper bound of the sub-problem, expressed as:
the subproblem is a max-min bilayer structure, due to the inner layer constraint range YsCompletely unrelated to the outer layer constraint range psi, so that the inner layer min problem is solved in parallel, the worst probability distribution of the outer layer is searched according to the inner layer solving result,
Ψ is a set interval of the scene probability distribution, representing the confidence set bounded by the 1-norm and ∞ -norm:
in the formula, theta1And theta∞To allow maximum deviation of the probability distribution, α1And alpha∞Respectively uncertainty probability confidence under two norm constraint conditions,representing a set of positive real numbers, hsFor intermediate variables of construction, p0Expressing the initial probability, and K expressing the number of actual operation scenes, which is obtained by historical data;
after the main problem and the sub problem are decomposed, the solving steps are as follows:
step 1): setting an initial value, including:
the number of iterations m is 1, the lower bound L is 0, the upper bound U is + ∞,the superscript m indicates the number of iterations;
step 2): solving a main problem, comprising:
find the optimal solution x*And L(m)*And updating the lower limit value L ═ max { L, L(m)*};
Step 3): solving the result x in the main problem*Solving the subproblems on the basis of the obtained probability distribution of the worst sceneAnd U(m)*And updating the lower bound value U ═ min { U, U ═(m)*};
Step 4): judging whether the upper and lower bound gaps are smaller than the convergence precision, if so, stopping iteration and returning to the optimal solution x*(ii) a If not, updating scene probability distribution in the main problemAnd define new variables in the main problemAnd adding a correlation constraint Ys (m+1);
Step 5): updating m to m +1, and returning to the step 2);
when iteration is terminated, the upper bound value and the lower bound value are unified, the optimal solution in the power distribution network accessed by the virtual power plant at the moment is determined according to the upper bound value and the lower bound value, and the optimal solution comprises the daily transaction electric quantity with the VPP of the power distribution network in an uncertain environmentAnd carrying in the target function minF according to the optimal solution to obtain the running cost.
A coordinated optimization system for a virtual power plant and a power distribution network containing distributed power supplies comprises:
the acquisition module is used for acquiring network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of a power distribution network accessed by a current virtual power plant;
the optimization model processing module is used for inputting network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of the power distribution network accessed by the current virtual power plant into a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain daily transaction electric quantity and operation cost of the power distribution network; the two stages comprise a first stage model and a second stage model, wherein the first stage model is used for constraining the operation domain of each period of the equipment in the VPP to obtain the integral output of each period of the VPP; the second-stage model is used for carrying out power distribution network optimization scheduling by using the result of the first-stage model, and solving to obtain daily transaction electric quantity and operation cost of the power distribution network;
a VPP internal constraint stage and a power distribution network optimization scheduling stage based on the result of the VPP internal constraint stage;
the construction of the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes comprises the following steps:
constructing a two-stage power distribution network coordination optimization model containing a VPP, wherein the VPP is a virtual power plant of a distributed power supply constructed on the basis of a distributed photovoltaic power generation system, an energy storage battery, a gas turbine and a controllable load which are connected into a power distribution network; and considering the uncertainty of photovoltaic output, and constructing a multi-discrete scene-based two-stage power distribution network VPP distribution robust coordination optimization model based on the two-stage power distribution network coordination optimization model containing VPP.
Further, the two-stage power distribution network coordination optimization model containing the VPP comprises:
the first stage model, the objective function is the running cost of the VPP in the scheduling period, and is expressed as:
in the formula (I), the compound is shown in the specification,cost factors for the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively,the rates of adjustment of the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively;
the VPP running cost objective function in the scheduling period comprises the following constraints:
1) DG constraints
In the formula, Pi DG,minAnd Pi DG,maxRespectively DG output powerUpper and lower limits of (d);andrespectively representing upward and downward climbing rate limits of the DG, wherein t and t +1 respectively represent two adjacent time periods in front and back, and the formula (1-1) and the formula (1-2) respectively represent DG output constraint and climbing rate constraint;
2) ESS constraints
In the formula (I), the compound is shown in the specification,andrepresents the charge and discharge power of the ESS,andidentified by 0-1 for the charging and discharging state of the ESS,indicating that the device is in a charging state,indicating a discharging or idle state, the ESS cannot be charged and discharged simultaneously at the same time;represents the upper limit of the charging and discharging power of the ESS;andas is the charge-discharge coefficient of the ESS,andrepresenting the lower limit and the upper limit of the capacity of the ESS, and respectively representing energy storage charge-discharge power limit and energy storage electric quantity constraint by an equation (1-3) and an equation (1-4);
3) SL constraint
In the formula Pi SL,down Pi SL,upRespectively SL load removal and loadShifting into a maximum value; pi SL,maxThe maximum load translation amount;for the load non-translatable period, equations (1-5) represent a load translation power constraint, and equations (1-6) represent a load translation power balance constraint, a load translation power total constraint and a non-translatable period constraint;
4) IL constraint
In the formula (I), the compound is shown in the specification,for the power of the call for the IL,is a 0-1 variable, P, representing the calling state of ILi IL,maxAn upper limit for power per call;for the upper limit of the number of calls for IL in a scheduling period, TmaxAnd TminRespectively the maximum continuous calling times and the minimum continuous non-called times;for the non-callable period, equations (1-7) represent an IL call power constraint, equations (1-8) represent a call number constraint, a continuous non-call number constraint, and a non-callable period constraint;
5) PV restraint
The active power of the distributed photovoltaic is set to be in a maximum power point tracking mode, the photovoltaic is connected into the power distribution network through the inverter, and therefore the reactive power of the photovoltaic is adjustable and limited by the capacity of the inverter:
in the formula:representing the active power of the photovoltaic inverter during the period t,representing the reactive power of the photovoltaic inverter during the period t,is the maximum apparent power of the photovoltaic inverter;
and in the second stage model, the optimization target is the minimum cost in the operation period of the power distribution network, and the target function minF is as follows:
in the formula, DT is a time interval, and T is a scheduling period; etabuy,b、Respectively the electricity price for purchasing electricity in the day ahead and the electricity price for purchasing electricity in the spot market,selling electricity for the distribution network; b and N are the number of load nodes of the power distribution network and the number of VPPs respectively; pt B、Pt R、The method comprises the following steps of respectively purchasing electric quantity in the day ahead, purchasing electric quantity in the spot market and using electric load of a user;calling power for the VPP, obtained by a first stage model optimization:
representing the active power of the photovoltaic in the VPP at time t,representing the discharge power of the stored energy in VPP at time t,representing the heavy electric power stored in the VPP at time t,
the objective function of the second stage model contains the following constraints:
1) flow restraint
Vj,t 2=Vi,t 2-2(Pij,trij+Qij,txij)+Iij,t 2(rij 2+xij 2)
J → k represents the set of all line end nodes k pointed by the node j as the head end; r isijRepresenting the resistance, x, on branch ijijRepresents the reactance of branch ij; i isij,tRepresents the current on branch ij; vi,tRepresenting the voltage assignment at node i, Pij,tAnd Qij,tRespectively representing active power and reactive power at the head end of the branch ij;andrepresents the active and reactive injection of the jth VPP;indicating the reactive compensation quantity, P, of a continuous type reactive compensation devicejk,tI → j represents the set of all line end nodes j pointed to by node i as the head end,representing the active load, Q, of node jjk,tRepresenting the reactive power at the head end of branch jk,the PV reactive power is represented by the PV reactive power,representing reactive load of node j, Vj,tRepresents the voltage magnitude at node j;
the above equation is further relaxed as a second order cone constraint, as follows:
2) power balance constraint
In the formula Pt lossThe active loss of the network is equivalent to the sum of active power injected by all nodes;
3) voltage safety constraints
In the formula:andrespectively representing the allowable voltage V of the systemj,tUpper and lower limits;
4) reactive power compensator restraint
In the formula:andreactive compensation permitted for the reactive compensation device respectivelyA lower limit and an upper limit.
Further, the optimization model processing module comprises a model construction module for constructing a two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes, and the model construction module is represented as follows:
Ax≤c (2)
Ex+Fys≤d (3)
||Mys+o||2≤qTys+n (4)
Hys≤j (5)
Gys=ξs (6)
in formula (1): x represents a first stage variable comprising:a is a cost coefficient corresponding to the output decision of different equipment; y issThe second-stage variables under the scene s comprise: vj,t,Iij,t, Pij,t,Qij,t,psIs the probability of occurrence of scene s; a, c, d, E, F, G, H, j, M, n, o and q are all vectors or coefficient matrixes corresponding to variables in the model; xisPredicting an output vector for the PV; n is a radical ofsRepresenting a limited number of discrete scenes, NsK actual scenes are obtained from the limited discrete scenes through historical data and are obtained through scene clustering method screening; equation (2) represents all constraints associated with the first stage variables; equation (3) represents the constraint associated with the first stage variable and the second stage variable; equation (4) represents a second order cone relaxation constraint; equation (5) represents the relevant constraint of the second stage variable; equation (6) represents the equality constraint of the photovoltaic power generation uncertainty predicted output.
Further, the input is performed to a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain the daily transaction electric quantity and the operation cost of the power distribution network, and the method comprises the following steps:
and solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multi-discrete scene by adopting a column and constraint generation algorithm to obtain the daily trading electric quantity and the operating cost of the power distribution network with the VPP under the uncertain environment.
Further, the method for solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes by adopting the column and constraint generation algorithm to obtain the power distribution network intra-day and VPP transaction electric quantity and the operation cost under the uncertain environment comprises the following steps:
decomposing the problem of solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes into a main problem and a sub-problem, wherein the main problem provides a lower bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the sub-problem provides an upper bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the upper bound and the lower bound are gradually closed through continuous iteration, when the difference value of the two bounds is smaller than a preset value, the iteration is stopped, an optimal solution is returned, and the power distribution network transaction power quantity and the operation cost in the day with the VPP under an uncertain environment are obtained;
the lower bound of the main question, denoted:
in the formula (I), the compound is shown in the specification,for the probability distribution found by the sub-problem,m is a second-stage variable flexibly adjusted according to the scene, and is the total number of model iterations;
the upper bound of the sub-problem, expressed as:
the subproblem is a max-min bilayer structure, due to the inner layer constraint range YsCompletely unrelated to the outer layer constraint range psi, so that the inner layer min problem is solved in parallel, the worst probability distribution of the outer layer is searched according to the inner layer solving result,
Ψ is a set interval of the scene probability distribution, representing the confidence set bounded by the 1-norm and ∞ -norm:
in the formula, theta1And theta∞To allow maximum deviation of the probability distribution, α1And alpha∞Respectively uncertainty probability confidence under two norm constraint conditions,representing a set of positive real numbers, hsFor intermediate variables of construction, p0Expressing the initial probability, and K expressing the number of actual operation scenes, which is obtained by historical data;
after the main problem and the sub problem are decomposed, the solving steps are as follows:
step 1): setting an initial value, including:
the number of iterations m is 1, the lower bound L is 0, the upper bound U is + ∞,the superscript m indicates the number of iterations;
step 2): solving a main problem, comprising:
find the optimal solution x*And L(m)*And updating the lower limit value L ═ max { L, L(m)*};
Step 3): solving the result x in the main problem*Solving the subproblems on the basis of the obtained probability distribution of the worst sceneAnd U(m)*And updating the lower bound value U ═ min { U, U ═(m)*};
Step 4): judging whether the upper and lower bound gaps are smaller than the convergence precision, if so, stopping iteration and returning to the optimal solution x*(ii) a If not, updating scene probability distribution in the main problemAnd define new variables in the main problemAnd adding a correlation constraint Ys (m+1);
Step 5): updating m to m +1, and returning to the step 2);
when iteration is terminated, the upper bound value and the lower bound value are unified, the optimal solution in the power distribution network accessed by the virtual power plant at the moment is determined according to the upper bound value and the lower bound value, and the optimal solution comprises the daily transaction electric quantity with the VPP of the power distribution network in an uncertain environmentAnd carrying in the target function minF according to the optimal solution to obtain the running cost.
The invention achieves the following beneficial effects:
1) the VPP model established by the method carries out most economic optimization on the output of each unit in the VPP on the premise of ensuring the operation of photovoltaic MPPT, thereby not only improving the consumption level of renewable energy sources, but also optimizing the economical efficiency of a system.
2) The power distribution network with VPP participation is optimally scheduled based on the time-of-use electricity price, so that the electricity purchasing cost of the power distribution network can be reduced, the electricity selling income is improved, and the peak clipping and valley filling can be realized.
3) The distributed robust optimization model considering the uncertainty of the distributed power supply can better balance the economy and the robustness and obtain higher benefits.
Drawings
FIG. 1 is a diagram of a VPP coordination control strategy.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
A distribution robust optimization operation strategy of a power distribution network comprising a virtual power plant comprises the following steps:
step (1): a VPP coordination control strategy is adopted, and a VPP coordination control center is responsible for regulating and controlling each power generation unit, energy storage unit and load unit in the VPP coordination control center and carrying out optimization decision in coordination with a power distribution network;
step (2): constructing a power distribution network coordination optimization model containing VPP, and decomposing variables into two stages by adopting a box decomposition algorithm to solve: bringing the constraint in the VPP into a first stage, and constraining the operation domain of each time period of the equipment in the VPP to obtain the integral output of each time period of the VPP; in the second stage, the result of the first stage is utilized to carry out power distribution network optimization scheduling, and the daily transaction electric quantity and the operation cost of the power distribution network are obtained through solving;
and (3): the uncertainty of photovoltaic output is considered, a two-stage power distribution network VPP distribution robust coordination optimization model based on a multi-discrete scene is constructed, and the model is iteratively solved by adopting a column and constraint generation (C & CG) algorithm.
Further, in step (1), the essence of the VPP is to integrally manage different areas and types of power generation resources, and the power distribution network does not directly control the power generation units or the energy storage devices during operation, but controls the VPP to participate in operation and scheduling of the power grid in an integrated manner. As shown in fig. 1, distributed photovoltaic packaging integration into a power distribution grid is incorporated herein, together with energy storage batteries (ESS), gas turbines (DG), and controllable loads, to form a VPP.
Further, in the step (2), operation optimization in a scheduling period is performed on the power distribution network with the VPP based on the time-of-use electricity price, the power distribution network firstly signs an electricity purchasing contract to purchase most of electricity based on load prediction electricity quantity in the day, and the surplus electricity quantity and the difference electricity quantity are exchanged on the spot market. Because the model has more related variables and more constraints, the box decomposition algorithm is adopted to decompose the variables into two stages for solving: bringing the constraint in the VPP into a first stage, and constraining the operation domain of each time period of the equipment in the VPP to obtain the integral output of each time period of the VPP; and in the second stage, the result of the first stage is utilized to carry out power distribution network optimization scheduling, and the daily transaction electric quantity and the operation cost of the power distribution network are obtained through solving.
For the first stage model, the objective function is the operating cost of the VPP in the scheduling period, where ESS and DG are regulated, photovoltaic is not regulated and the generation cost is not counted. IL and SL participate in VPP scheduling by contracting:
in the formula (I), the compound is shown in the specification,the cost coefficients of DG, IL, SL respectively,for their respective call rates.
The following constraints are included:
1) DG constraints
In the formula, Pi DG,minAnd Pi DG,maxRespectively an upper limit and a lower limit of DG output power;andup and down ramp rate limits for DG, respectively. The above equations represent DG output constraint and ramp rate constraint, respectively.
2) ESS constraints
In the formula (I), the compound is shown in the specification,andrepresents the charge and discharge power of the ESS,andidentified by 0-1 for the charging and discharging state of the ESS,indicating that the device is in a charging state,indicating a discharging or idle state, the ESS cannot be charged and discharged simultaneously at the same time;represents the upper limit of the charging and discharging power of the ESS;andas is the charge-discharge coefficient of the ESS,andrepresenting the lower and upper capacity limits of the ESS. The above formula represents the energy storage charge and discharge power limit and the energy storage electric quantity constraint respectively.
3) SL constraint
In the formula Pi SL,down Pi SL,upSL load shift out and load shift in maximum, respectively; pi SL,maxThe maximum load translation amount;a load non-translatable period. The above equations represent the load translation power constraint, the load translation power balance constraint, the load translation power total constraint, and the non-translation time period constraint, respectively.
4) IL constraint
In the formulaIs a 0-1 variable, P, representing the calling state of ILi IL,maxAn upper limit for power per call;for the upper limit of the number of calls for IL in a scheduling period, TmaxAnd TminRespectively the maximum continuous calling times and the minimum continuous non-called times;is a non-callable period. The above equations respectively represent an IL call power constraint, a call number constraint, a consecutive non-call number constraint, and a non-call period constraint.
5) PV restraint
According to the national photovoltaic agricultural policy, in the model, the active power of the distributed photovoltaic is set to be a Maximum Power Point Tracking (MPPT) mode, and the photovoltaic is connected to the power distribution network through the inverter, so that the reactive power of the photovoltaic is adjustable and is limited by the capacity of the inverter:
in the formula:representing the reactive power of the photovoltaic inverter during the period t,is the maximum apparent power of the photovoltaic inverter.
For the second stage model, the optimization target is that the cost in the operation period of the power distribution network is minimum, and the target function is as follows:
in the formula, DT is a time interval, and T is a scheduling period; etabuy,b Respectively the electricity prices of the day-ahead and spot market purchase,selling electricity for the distribution network; b and N are the number of load nodes of the power distribution network and the number of VPPs respectively; pt B Pt R Respectively purchasing electric quantity and user electricity utilization load quantity for the day-ahead and spot market;calling power for the VPP, obtained by a first stage model optimization:
the following constraints are included:
1) flow restraint
Vj,t 2=Vi,t 2-2(Pij,trij+Qij,txij)+Iij,t 2(rij 2+xij 2)
In the formula: j → k represents the set of all line end nodes k pointed by the node j as the head end; r isijRepresenting the resistance, x, on branch ijijRepresents the reactance of branch ij; i isij,tRepresents the current on branch ij; vi,tRepresenting the voltage at node i, Pij,tAnd Qij,tRespectively representing active power and reactive power at the head end of the branch ij;andrepresents the active and reactive injection of the kth VPP;the reactive compensation amount of the continuous reactive compensation device is shown.
Since the power flow constraint exhibits higher nonlinearity, for the convenience of model simplification, the above equation can be further relaxed into a second-order cone constraint, as shown below:
2) power balance constraint
In the formula Pt lossThe network active loss is equivalent to the sum of active power injected by all nodes.
3) Voltage safety constraints
In the formula:andrespectively representing the upper and lower voltage limits allowed by the system.
4) Reactive power compensator restraint
In the formula:andrespectively, the lower limit and the upper limit allowed by the reactive power compensation device.
Further, in step (3), due to the high uncertainty of PV output, a great challenge is brought to the optimal scheduling of VPP. The uncertainty of the PV output is processed by adopting a distributed robust optimization method, K actual scenes are obtained through the assumed historical data, and N is obtained through screening by certain scene clustering meanssAnd (4) obtaining the worst probability distribution of the finite scene under the known decision of the first-stage model through optimization. In order to limit the fluctuation change of probability distribution under uncertainty, a confidence set of 1-norm and infinity-norm is introduced for comprehensive constraint, and a distributed robust optimization model based on a discrete scene is constructed as follows:
Ax≤c (2)
Ex+Fys≤d (3)
||Mys+o||2≤qTys+n (4)
Hys≤j (5)
Gys=ξs (6)
in formula (1): x represents the first stage variables, including DG, ESS, SL, IL, PV decisions, i.e. a is a cost coefficient corresponding to the output decision of different equipment; y issIs a second stage variable under the scene s, comprising a state variable and a continuous reactive power supplementing device action decision, namely Vj,t,Iij,t,Pij,t, Qij,t,psIs the probability of occurrence of scene s; a, c, d, E, F, G, H, j, M, n, o and q are all vectors or coefficient matrixes, ξ, corresponding to variables in the modelsThe force vector is predicted for the PV. Equation (2) represents all constraints associated with the first stage variables; equation (3) represents the constraint associated with the first stage variable and the second stage variable, such as the tidal flow constraint; equation (4) represents a second order cone relaxation constraint; equation (5) represents the relevant constraint of the second stage variable; equation (6) represents the equality constraint of the photovoltaic power generation uncertainty predicted output.
Ψ is a set interval of the scene probability distribution, representing the confidence set bounded by the 1-norm and ∞ -norm:
in the formula [ theta ]1And theta∞To allow for the maximum value of the probability distribution deviation, assume α1And alpha∞Respectively, uncertainty probability confidence under two norm constraint conditions, then:
the method adopts a column constraint generation algorithm (C & CGA) to carry out decoupling solution, and the basic idea is as follows: and decomposing the original problem into a main problem and a subproblem, wherein the main problem provides a lower bound for the model, the subproblem provides an upper bound for the model, the upper bound and the lower bound are gradually closed through continuous iteration, and when the difference value between the upper bound and the lower bound is smaller than a preset value, the iteration is stopped and the optimal solution is returned.
Solving the optimal solution x satisfying the system constraint on the premise of known probability distribution*The lower bound L of the entire model is given.
In the formula (I), the compound is shown in the specification,for a known (by sub-problem) probability distribution,and M is the total number of model iterations for a second stage variable which can be flexibly adjusted according to the scene.
Variable optimal solution x of subproblems in a known first stage*On the premise of (1), the worst scene probability distribution in the confidence interval is obtained, and the upper bound U of the whole model is given.
The subproblem is a max-min bilayer structure, due to the inner layer constraint range YsAnd the method is completely irrelevant to the outer layer constraint range psi, so that the inner layer min problem can be solved in parallel firstly, and then the worst probability distribution of the outer layer is found according to the inner layer solving result.
Wherein the optimal solution x of the main problem*And substituting the inner layer problem for iteration.
After the distribution robust optimization model of the power distribution network is decomposed by C & CGA, the overall solving steps are as follows:
1): setting an initial value. The number of iterations m is 1, the lower bound L is 0, the upper bound U is + ∞,
2): and solving the main problem. Find the optimal solution x*And L(m)*And updating the lower limit value L ═ max { L, L(m)*};
3): solving the result x in the main problem*Solving the subproblems on the basis of the obtained probability distribution of the worst sceneAnd U(m)*And updating the lower bound value U ═ min { U, U ═(m)*};
4): judging whether the upper and lower bound gaps are smaller than the convergence precision, if so, stopping iteration and returning to the optimal solution x*(ii) a If not, updating scene probability distribution in the main problemAnd define new ones in the main questionVariables ofAnd adding a correlation constraint Ys (m+1);
5): and updating m to m +1, and returning to the second step.
Correspondingly, the invention also provides a coordinated optimization system of the virtual power plant containing the distributed power supply and the power distribution network, which comprises the following steps:
the acquisition module is used for acquiring network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of a power distribution network accessed by a current virtual power plant;
the optimization model processing module is used for inputting network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of the power distribution network accessed by the current virtual power plant into a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain daily transaction electric quantity and operation cost of the power distribution network; the two stages comprise a first stage model and a second stage model, wherein the first stage model is used for constraining the operation domain of each period of the equipment in the VPP to obtain the integral output of each period of the VPP; the second-stage model is used for carrying out power distribution network optimization scheduling by using the result of the first-stage model, and solving to obtain daily transaction electric quantity and operation cost of the power distribution network;
a VPP internal constraint stage and a power distribution network optimization scheduling stage based on the result of the VPP internal constraint stage;
the construction of the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes comprises the following steps:
constructing a two-stage power distribution network coordination optimization model containing a VPP, wherein the VPP is a virtual power plant of a distributed power supply constructed on the basis of a distributed photovoltaic power generation system, an energy storage battery, a gas turbine and a controllable load which are connected into a power distribution network; and considering the uncertainty of photovoltaic output, and constructing a multi-discrete scene-based two-stage power distribution network VPP distribution robust coordination optimization model based on the two-stage power distribution network coordination optimization model containing VPP.
Further, the two-stage power distribution network coordination optimization model containing the VPP comprises:
the first stage model, the objective function is the running cost of the VPP in the scheduling period, and is expressed as:
in the formula (I), the compound is shown in the specification,cost factors for the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively,the rates of adjustment of the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively;
the VPP running cost objective function in the scheduling period comprises the following constraints:
1) DG constraints
In the formula, Pi DG,minAnd Pi DG,maxRespectively DG output powerUpper and lower limits of (d);andrespectively representing the upward and downward climbing rate limits of the DG, wherein t and t +1 respectively represent two adjacent time periods, and the formula (1-1) and the formula (1-2) respectively represent DG output constraintAnd a ramp rate constraint;
2) ESS constraints
In the formula (I), the compound is shown in the specification,andrepresents the charge and discharge power of the ESS,andidentified by 0-1 for the charging and discharging state of the ESS,indicating that the device is in a charging state,indicating a discharging or idle state, the ESS cannot be charged and discharged simultaneously at the same time;represents the upper limit of the charging and discharging power of the ESS;andas is the charge-discharge coefficient of the ESS,andrepresenting the lower limit and the upper limit of the capacity of the ESS, and respectively representing energy storage charge-discharge power limit and energy storage electric quantity constraint by an equation (1-3) and an equation (1-4);
3) SL constraint
In the formula Pi SL,down Pi SL,upRespectively SL load removal and loadShifting into a maximum value; pi SL,maxThe maximum load translation amount;for the load non-translatable period, equations (1-5) represent a load translation power constraint, and equations (1-6) represent a load translation power balance constraint, a load translation power total constraint and a non-translatable period constraint;
4) IL constraint
In the formula (I), the compound is shown in the specification,for the power of the call for the IL,is a 0-1 variable, P, representing the calling state of ILi IL,maxAn upper limit for power per call;for the upper limit of the number of calls for IL in a scheduling period, TmaxAnd TminRespectively the maximum continuous calling times and the minimum continuous non-called times;for the non-callable period, equations (1-7) represent an IL call power constraint, equations (1-8) represent a call number constraint, a continuous non-call number constraint, and a non-callable period constraint;
5) PV restraint
The active power of the distributed photovoltaic is set to be in a maximum power point tracking mode, the photovoltaic is connected into the power distribution network through the inverter, and therefore the reactive power of the photovoltaic is adjustable and limited by the capacity of the inverter:
in the formula:representing the active power of the photovoltaic inverter during the period t,representing the reactive power of the photovoltaic inverter during the period t,is the maximum apparent power of the photovoltaic inverter;
and in the second stage model, the optimization target is the minimum cost in the operation period of the power distribution network, and the target function minF is as follows:
in the formula, Δ T is a time interval, and T is a scheduling period; etabuy,b、Respectively the electricity price for purchasing electricity in the day ahead and the electricity price for purchasing electricity in the spot market,selling electricity for the distribution network; b and N are the number of load nodes of the power distribution network and the number of VPPs respectively; pt B、Pt R、The method comprises the following steps of respectively purchasing electric quantity in the day ahead, purchasing electric quantity in the spot market and using electric load of a user;calling power for the VPP, obtained by a first stage model optimization:
representing the active power of the photovoltaic in the VPP at time t,representing the discharge power of the stored energy in VPP at time t,representing the heavy electric power stored in the VPP at time t,
the objective function of the second stage model contains the following constraints:
1) flow restraint
Vj,t 2=Vi,t 2-2(Pij,trij+Qij,txij)+Iij,t 2(rij 2+xij 2)
J → k represents the set of all line end nodes k pointed by the node j as the head end; r isijRepresenting the resistance, x, on branch ijijRepresents the reactance of branch ij; i isij,tRepresents the current on branch ij; vi,tRepresenting the voltage assignment at node i, Pij,tAnd Qij,tRespectively representing active power and reactive power at the head end of the branch ij;andrepresents the active and reactive injection of the jth VPP;indicating the reactive compensation quantity, P, of a continuous type reactive compensation devicejk,tI → j represents the set of all line end nodes j pointed to by node i as the head end,representing the active load, Q, of node jjk,tRepresenting the reactive power at the head end of branch jk,the PV reactive power is represented by the PV reactive power,representing reactive load of node j, Vj,tRepresents the voltage magnitude at node j;
the above equation is further relaxed as a second order cone constraint, as follows:
2) power balance constraint
In the formula Pt lossThe active loss of the network is equivalent to the sum of active power injected by all nodes;
3) voltage safety constraints
In the formula:andrespectively representing the allowable voltage V of the systemj,tUpper and lower limits;
4) reactive power compensator restraint
In the formula:andreactive compensation permitted for the reactive compensation device respectivelyA lower limit and an upper limit.
Further, the optimization model processing module comprises a model construction module for constructing a two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes, and the model construction module is represented as follows:
Ax≤c (2)
Ex+Fys≤d (3)
||Mys+o||2≤qTys+n (4)
Hys≤j (5)
Gys=ξs (6)
in formula (1): x represents a first stage variable comprising:a is a cost coefficient corresponding to the output decision of different equipment; y issThe second-stage variables under the scene s comprise: vj,t,Iij,t, Pij,t,Qij,t,psIs the probability of occurrence of scene s; a, c, d, E, F, G, H, j, M, n, o and q are all vectors or coefficient matrixes corresponding to variables in the model; xisPredicting an output vector for the PV; n is a radical ofsRepresenting a limited number of discrete scenes, NsK actual scenes are obtained from the limited discrete scenes through historical data and are obtained through scene clustering method screening; equation (2) represents all constraints associated with the first stage variables; equation (3) represents the constraint associated with the first stage variable and the second stage variable; equation (4) represents a second order cone relaxation constraint; equation (5) represents the relevant constraint of the second stage variable; formula (A), (B) and6) and (3) an equality constraint representing the uncertainty predicted output of the photovoltaic power generation.
Further, the input is performed to a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain the daily transaction electric quantity and the operation cost of the power distribution network, and the method comprises the following steps:
and solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multi-discrete scene by adopting a column and constraint generation algorithm to obtain the daily trading electric quantity and the operating cost of the power distribution network with the VPP under the uncertain environment.
Further, the method for solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes by adopting the column and constraint generation algorithm to obtain the power distribution network intra-day and VPP transaction electric quantity and the operation cost under the uncertain environment comprises the following steps:
decomposing the problem of solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes into a main problem and a sub-problem, wherein the main problem provides a lower bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the sub-problem provides an upper bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the upper bound and the lower bound are gradually closed through continuous iteration, when the difference value of the two bounds is smaller than a preset value, the iteration is stopped, an optimal solution is returned, and the power distribution network transaction power quantity and the operation cost in the day with the VPP under an uncertain environment are obtained;
the lower bound of the main question, denoted:
in the formula (I), the compound is shown in the specification,for the probability distribution found by the sub-problem,m is a second-stage variable flexibly adjusted according to the scene, and is the total number of model iterations;
the upper bound of the sub-problem, expressed as:
the subproblem is a max-min bilayer structure, due to the inner layer constraint range YsCompletely unrelated to the outer layer constraint range psi, so that the inner layer min problem is solved in parallel, the worst probability distribution of the outer layer is searched according to the inner layer solving result,
Ψ is a set interval of the scene probability distribution, representing the confidence set bounded by the 1-norm and ∞ -norm:
in the formula, theta1And theta∞To allow maximum deviation of the probability distribution, α1And alpha∞Respectively uncertainty probability confidence under two norm constraint conditions,representing a set of positive real numbers, hsFor intermediate variables of construction, p0Expressing the initial probability, and K expressing the number of actual operation scenes, which is obtained by historical data;
after the main problem and the sub problem are decomposed, the solving steps are as follows:
step 1): setting an initial value, including:
the number of iterations m is 1, the lower bound L is 0, the upper bound U is + ∞,the superscript m indicates the number of iterations;
step 2): solving a main problem, comprising:
find the optimal solution x*And L(m)*And updating the lower limit value L ═ max { L, L(m)*};
Step 3): solving the result x in the main problem*Solving the subproblems on the basis of the obtained probability distribution of the worst sceneAnd U(m)*And updating the lower bound value U ═ min { U, U ═(m)*};
Step 4): judging whether the upper and lower bound gaps are smaller than the convergence precision, if so, stopping iteration and returning to the optimal solution x*(ii) a If not, updating scene probability distribution in the main problemAnd define new variables in the main problemAnd adding a correlation constraint Ys (m+1);
Step 5): updating m to m +1, and returning to the step 2);
when iteration is terminated, the upper bound value and the lower bound value are unified, and the power distribution network accessed by the virtual power plant at the moment is determined according to the upper bound value and the lower bound valueThe optimal solution comprises the daily trading electric quantity with the VPP of the power distribution network under the uncertain environmentAnd carrying in the target function minF according to the optimal solution to obtain the running cost.
Aiming at the uncertainty of renewable energy, the power distribution network distribution robust optimization model considering VPP is provided, and the power distribution network distribution robust optimization model has the following advantages:
1) the VPP model established by the method carries out most economic optimization on the output of each unit in the VPP on the premise of ensuring the operation of photovoltaic MPPT, thereby not only improving the consumption level of renewable energy sources, but also optimizing the economical efficiency of a system.
2) The power distribution network with VPP participation is optimally scheduled based on the time-of-use electricity price, so that the electricity purchasing cost of the power distribution network can be reduced, the electricity selling income is improved, and the peak clipping and valley filling can be realized.
3) The distributed robust optimization model considering the uncertainty of the distributed power supply can better balance the economy and the robustness and obtain higher benefits.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A coordinated optimization method for a virtual power plant and a power distribution network with distributed power supplies is characterized by comprising the following steps:
acquiring network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of a power distribution network accessed by a current virtual power plant;
inputting the power distribution network VPP distribution robust coordination optimization model to a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain the daily transaction electric quantity and the operation cost of the power distribution network; the two stages comprise a first stage model and a second stage model, wherein the first stage model is used for constraining the operation domain of each period of the equipment in the VPP to obtain the integral output of each period of the VPP; the second-stage model is used for carrying out power distribution network optimization scheduling by using the result of the first-stage model, and solving to obtain daily transaction electric quantity and operation cost of the power distribution network;
a VPP internal constraint stage and a power distribution network optimization scheduling stage based on the result of the VPP internal constraint stage;
the construction of the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes comprises the following steps:
constructing a two-stage power distribution network coordination optimization model containing a VPP, wherein the VPP is a virtual power plant of a distributed power supply constructed on the basis of a distributed photovoltaic power generation system, an energy storage battery, a gas turbine and a controllable load which are connected into a power distribution network; and considering the uncertainty of photovoltaic output, and constructing a multi-discrete scene-based two-stage power distribution network VPP distribution robust coordination optimization model based on the two-stage power distribution network coordination optimization model containing VPP.
2. The coordinated optimization method for the virtual power plant and the power distribution network with the distributed power supplies according to claim 1, wherein the coordinated optimization model for the two-stage power distribution network with the VPP comprises the following steps:
the first stage model, the objective function is the running cost of the VPP in the scheduling period, and is expressed as:
in the formula (I), the compound is shown in the specification,cost factors for the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively,the rates of adjustment of the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively;
the VPP running cost objective function in the scheduling period comprises the following constraints:
1) DG constraints
In the formula, Pi DG,minAnd Pi DG,maxRespectively DG output powerUpper and lower limits of (d);andrespectively representing upward and downward climbing rate limits of the DG, wherein t and t +1 respectively represent two adjacent time periods in front and back, and the formula (1-1) and the formula (1-2) respectively represent DG output constraint and climbing rate constraint;
2) ESS constraints
In the formula (I), the compound is shown in the specification,andrepresents the charge and discharge power of the ESS,andidentified by 0-1 for the charging and discharging state of the ESS,indicating that the device is in a charging state,indicating a discharging or idle state, the ESS cannot be charged and discharged simultaneously at the same time; pj ESS,maxRepresents the upper limit of the charging and discharging power of the ESS;andas is the charge-discharge coefficient of the ESS,andrepresenting the lower limit and the upper limit of the capacity of the ESS, and respectively representing energy storage charge-discharge power limit and energy storage electric quantity constraint by an equation (1-3) and an equation (1-4);
3) SL constraint
In the formula Pi SL,down Pi SL,upRespectively SL load removal and loadShifting into a maximum value; pi SL,maxThe maximum load translation amount;for the load non-translatable period, equations (1-5) represent a load translation power constraint, and equations (1-6) represent a load translation power balance constraint, a load translation power total constraint and a non-translatable period constraint;
4) IL constraint
In the formula (I), the compound is shown in the specification,for the power of the call for the IL,is a 0-1 variable, P, representing the calling state of ILi IL,maxAn upper limit for power per call;for the upper limit of the number of calls for IL in a scheduling period, TmaxAnd TminRespectively the maximum continuous calling times and the minimum continuous non-called times;for the non-callable period, equations (1-7) represent the IL call power constraint, and equations (1-8) represent the call count constraint, the number of consecutive callsConstraint, continuous non-calling times constraint and non-calling time constraint;
5) PV restraint
The active power of the distributed photovoltaic is set to be in a maximum power point tracking mode, the photovoltaic is connected into the power distribution network through the inverter, and therefore the reactive power of the photovoltaic is adjustable and limited by the capacity of the inverter:
in the formula:representing the active power of the photovoltaic inverter during the period t,representing the reactive power of the photovoltaic inverter during the period t,is the maximum apparent power of the photovoltaic inverter;
and in the second stage model, the optimization target is the minimum cost in the operation period of the power distribution network, and the target function minF is as follows:
in the formula, Δ T is a time interval, and T is a scheduling period; etabuy,b、Respectively the electricity price for purchasing electricity in the day ahead and the electricity price for purchasing electricity in the spot market,selling electricity for the distribution network; b and N are the number of load nodes of the power distribution network and the number of VPPs respectively; pt B、Pt R、The method comprises the following steps of respectively purchasing electric quantity in the day ahead, purchasing electric quantity in the spot market and using electric load of a user;calling power for the VPP, obtained by a first stage model optimization:
representing the active power of the photovoltaic in the VPP at time t,representing the discharge power of the stored energy in VPP at time t,representing the heavy electric power stored in the VPP at time t,
the objective function of the second stage model contains the following constraints:
1) flow restraint
Vj,t 2=Vi,t 2-2(Pij,trij+Qij,txij)+Iij,t 2(rij 2+xij 2)
J → k represents the set of all line end nodes k pointed by the node j as the head end; r isijRepresenting the resistance, x, on branch ijijRepresents the reactance of branch ij; i isij,tRepresents the current on branch ij; vi,tRepresenting the voltage assignment at node i, Pij,tAnd Qij,tRespectively representing active power and reactive power at the head end of the branch ij;andrepresents the active and reactive injection of the jth VPP;indicating the reactive compensation quantity, P, of a continuous type reactive compensation devicejk,tI → j represents the set of all line end nodes j pointed to by node i as the head end,representing the active load, Q, of node jjk,tRepresenting the reactive power at the head end of branch jk,the PV reactive power is represented by the PV reactive power,representing reactive load of node j, Vj,tRepresents the voltage magnitude at node j;
the above equation is further relaxed as a second order cone constraint, as follows:
2) power balance constraint
In the formula Pt lossThe active loss of the network is equivalent to the sum of active power injected by all nodes;
3) voltage safety constraints
In the formula:andrespectively representing the allowable voltage V of the systemj,tUpper and lower limits;
4) reactive power compensator restraint
3. The coordinated optimization method for the virtual power plant and the power distribution network with the distributed power supplies according to claim 2, wherein the uncertainty of the photovoltaic output is considered, and a multi-discrete-scene-based two-stage power distribution network VPP distribution robust coordinated optimization model is constructed based on the two-stage power distribution network coordinated optimization model with the VPP, and is expressed as:
Ax≤c (2)
Ex+Fys≤d (3)
||Mys+o||2≤qTys+n (4)
Hys≤j (5)
Gys=ξs (6)
in formula (1): x represents a first stage variable comprising:a is a cost coefficient corresponding to the output decision of different equipment; y issThe second-stage variables under the scene s comprise: vj,t,Iij,t,Pij,t,Qij,t,psIs the probability of occurrence of scene s; a, c, d, E, F, G, H, j, M, n, o and q are all vectors or coefficient matrixes corresponding to variables in the model; xisPredicting an output vector for the PV; n is a radical ofsRepresenting a limited number of discrete scenes, NsK actual scenes are obtained from the limited discrete scenes through historical data and are obtained through scene clustering method screening; equation (2) represents all constraints associated with the first stage variables; equation (3) represents the constraint associated with the first stage variable and the second stage variable; equation (4) represents a second order cone relaxation constraint; equation (5) represents the relevant constraint of the second stage variable; equation (6) represents the equality constraint of the photovoltaic power generation uncertainty predicted output.
4. The coordinated optimization method for the virtual power plant and the power distribution network containing the distributed power supply as claimed in claim 3, wherein the input is to a pre-constructed two-stage power distribution network VPP distribution robust coordinated optimization model based on multiple discrete scenes to obtain the daily transaction electric quantity and the operation cost of the power distribution network, and the method comprises the following steps:
and solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multi-discrete scene by adopting a column and constraint generation algorithm to obtain the daily trading electric quantity and the operating cost of the power distribution network with the VPP under the uncertain environment.
5. The coordinated optimization method for the virtual power plant and the power distribution network with the distributed power supplies according to claim 4, wherein the two-stage power distribution network VPP distribution robust coordinated optimization model based on the multiple discrete scenes is solved by adopting a column and constraint generation algorithm to obtain the daily transaction electric quantity and the operation cost with the VPP of the power distribution network in the uncertain environment, and the method comprises the following steps:
decomposing the problem of solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes into a main problem and a sub-problem, wherein the main problem provides a lower bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the sub-problem provides an upper bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the upper bound and the lower bound are gradually closed through continuous iteration, when the difference value of the two bounds is smaller than a preset value, the iteration is stopped, an optimal solution is returned, and the power distribution network transaction power quantity and the operation cost in the day with the VPP under an uncertain environment are obtained;
the lower bound of the main question, denoted:
in the formula (I), the compound is shown in the specification,to pass through the subproblemThe probability distribution obtained is calculated according to the probability distribution,m is a second-stage variable flexibly adjusted according to the scene, and is the total number of model iterations;
the upper bound of the sub-problem, expressed as:
the subproblem is a max-min bilayer structure, due to the inner layer constraint range YsCompletely unrelated to the outer layer constraint range psi, so that the inner layer min problem is solved in parallel, the worst probability distribution of the outer layer is searched according to the inner layer solving result,
Ψ is a set interval of the scene probability distribution, representing the confidence set bounded by the 1-norm and ∞ -norm:
in the formula, theta1And theta∞To allow for a maximum value of the deviation of the probability distribution,α1and alpha∞Respectively uncertainty probability confidence under two norm constraint conditions,representing a set of positive real numbers, hsFor intermediate variables of construction, p0Expressing the initial probability, and K expressing the number of actual operation scenes, which is obtained by historical data;
after the main problem and the sub problem are decomposed, the solving steps are as follows:
step 1): setting an initial value, including:
the number of iterations m is 1, the lower bound L is 0, the upper bound U is + ∞,the superscript m indicates the number of iterations;
step 2): solving a main problem, comprising:
find the optimal solution x*And L(m)*And updating the lower limit value L ═ max { L, L(m)*};
Step 3): solving the result x in the main problem*Solving the subproblems on the basis of the obtained probability distribution of the worst sceneAnd U(m)*And updating the lower bound value U ═ min { U, U ═(m)*};
Step 4): judging whether the upper and lower bound gaps are smaller than the convergence precision, if so, stopping iteration and returning to the optimal solution x*(ii) a If not, updating scene probability distribution in the main problemAnd define new variables in the main problemAnd adding a correlation constraint Ys (m+1);
Step 5): updating m to m +1, and returning to the step 2);
when iteration is terminated, the upper bound value and the lower bound value are unified, the optimal solution in the power distribution network accessed by the virtual power plant at the moment is determined according to the upper bound value and the lower bound value, and the optimal solution comprises the daily transaction electric quantity with the VPP of the power distribution network in an uncertain environmentAnd carrying in the target function minF according to the optimal solution to obtain the running cost.
6. A coordinated optimization system of a virtual power plant and a power distribution network containing distributed power supplies is characterized by comprising the following components:
the acquisition module is used for acquiring network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of a power distribution network accessed by a current virtual power plant;
the optimization model processing module is used for inputting network parameters, line impedance, load data, equipment parameters and an uncertain variable distribution set of the power distribution network accessed by the current virtual power plant into a pre-constructed two-stage power distribution network VPP distribution robust coordination optimization model based on multiple discrete scenes to obtain daily transaction electric quantity and operation cost of the power distribution network; the two stages comprise a first stage model and a second stage model, wherein the first stage model is used for constraining the operation domain of each period of the equipment in the VPP to obtain the integral output of each period of the VPP; the second-stage model is used for carrying out power distribution network optimization scheduling by using the result of the first-stage model, and solving to obtain daily transaction electric quantity and operation cost of the power distribution network;
a VPP internal constraint stage and a power distribution network optimization scheduling stage based on the result of the VPP internal constraint stage;
the construction of the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes comprises the following steps:
constructing a two-stage power distribution network coordination optimization model containing a VPP, wherein the VPP is a virtual power plant of a distributed power supply constructed on the basis of a distributed photovoltaic power generation system, an energy storage battery, a gas turbine and a controllable load which are connected into a power distribution network; and considering the uncertainty of photovoltaic output, and constructing a multi-discrete scene-based two-stage power distribution network VPP distribution robust coordination optimization model based on the two-stage power distribution network coordination optimization model containing VPP.
7. The method for the coordinated optimization of the virtual power plant and the power distribution network with the distributed power supplies according to claim 6, wherein the VPP-containing two-stage power distribution network coordinated optimization model comprises:
the first stage model, the objective function is the running cost of the VPP in the scheduling period, and is expressed as:
in the formula (I), the compound is shown in the specification,cost factors for the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively,the rates of adjustment of the gas turbine DG, the interruptible load IL and the shiftable load SL, respectively;
the VPP running cost objective function in the scheduling period comprises the following constraints:
1) DG constraints
In the formula, Pi DG,minAnd Pi DG,maxRespectively DG output powerAbove the upper part of,A lower limit;andrespectively representing upward and downward climbing rate limits of the DG, wherein t and t +1 respectively represent two adjacent time periods in front and back, and the formula (1-1) and the formula (1-2) respectively represent DG output constraint and climbing rate constraint;
2) ESS constraints
In the formula (I), the compound is shown in the specification,andrepresents the charge and discharge power of the ESS,andidentified by 0-1 for the charging and discharging state of the ESS,indicating that the device is in a charging state,indicating a discharging or idle state, the ESS cannot be charged and discharged simultaneously at the same time;represents the upper limit of the charging and discharging power of the ESS;andas is the charge-discharge coefficient of the ESS,andrepresenting the lower limit and the upper limit of the capacity of the ESS, and respectively representing energy storage charge-discharge power limit and energy storage electric quantity constraint by an equation (1-3) and an equation (1-4);
3) SL constraint
In the formula Pi SL,down Pi SL,upRespectively SL load removal and loadShifting into a maximum value; pi SL,maxThe maximum load translation amount;for the load non-translatable period, equations (1-5) represent a load translation power constraint, and equations (1-6) represent a load translation power balance constraint, a load translation power total constraint and a non-translatable period constraint;
4) IL constraint
In the formula (I), the compound is shown in the specification,for the power of the call for the IL,is a 0-1 variable, P, representing the calling state of ILi IL,maxAn upper limit for power per call;for the upper limit of the number of calls for IL in a scheduling period, TmaxAnd TminRespectively the maximum continuous calling times and the minimum continuous non-called times;for the non-callable period, equations (1-7) represent an IL call power constraint, equations (1-8) represent a call number constraint, a continuous non-call number constraint, and a non-callable period constraint;
5) PV restraint
The active power of the distributed photovoltaic is set to be in a maximum power point tracking mode, the photovoltaic is connected into the power distribution network through the inverter, and therefore the reactive power of the photovoltaic is adjustable and limited by the capacity of the inverter:
in the formula:representing the active power of the photovoltaic inverter during the period t,representing the reactive power of the photovoltaic inverter during the period t,is the maximum apparent power of the photovoltaic inverter;
and in the second stage model, the optimization target is the minimum cost in the operation period of the power distribution network, and the target function minF is as follows:
in the formula, Δ T is a time interval, and T is a scheduling period; etabuy,b、Respectively the electricity price for purchasing electricity in the day ahead and the electricity price for purchasing electricity in the spot market,selling electricity for the distribution network; b and N are the number of load nodes of the power distribution network and the number of VPPs respectively; pt B、Pt R、The method comprises the following steps of respectively purchasing electric quantity in the day ahead, purchasing electric quantity in the spot market and using electric load of a user;calling power for the VPP, obtained by a first stage model optimization:
representing the active power of the photovoltaic in the VPP at time t,representing the discharge power of the stored energy in VPP at time t,representing the heavy electric power stored in the VPP at time t,
the objective function of the second stage model contains the following constraints:
1) flow restraint
Vj,t 2=Vi,t 2-2(Pij,trij+Qij,txij)+Iij,t 2(rij 2+xij 2)
J → k represents the set of all line end nodes k pointed by the node j as the head end; r isijRepresenting the resistance, x, on branch ijijRepresents the reactance of branch ij; i isij,tRepresents the current on branch ij; vi,tRepresenting the voltage assignment at node i, Pij,tAnd Qij,tRespectively representing active power and reactive power at the head end of the branch ij;andrepresents the active and reactive injection of the jth VPP;indicating the reactive compensation quantity, P, of a continuous type reactive compensation devicejk,tI → j represents the set of all line end nodes j pointed to by node i as the head end,representing the active load, Q, of node jjk,tRepresenting the reactive power at the head end of branch jk,the PV reactive power is represented by the PV reactive power,representing reactive load of node j, Vj,tRepresents the voltage magnitude at node j;
the above equation is further relaxed as a second order cone constraint, as follows:
2) power balance constraint
In the formula Pt lossThe active loss of the network is equivalent to the sum of active power injected by all nodes;
3) voltage safety constraints
In the formula:andrespectively representing the allowable voltage V of the systemj,tUpper and lower limits;
4) reactive power compensator restraint
8. The coordinated optimization method for the virtual power plant and the power distribution network containing the distributed power supplies according to claim 7, wherein the optimization model processing module comprises a model construction module for constructing a two-stage power distribution network VPP distribution robust coordinated optimization model based on multiple discrete scenes, and the model construction module is represented as follows:
Ax≤c (2)
Ex+Fys≤d (3)
||Mys+o||2≤qTys+n (4)
Hys≤j (5)
Gys=ξs (6)
in formula (1): x represents a first stage variable comprising:a is a cost coefficient corresponding to the output decision of different equipment; y issThe second-stage variables under the scene s comprise: vj,t,Iij,t,Pij,t,Qij,t,psIs the probability of occurrence of scene s; a, c, d, E, F, G, H, j, M, n, o and q are all vectors or coefficient matrixes corresponding to variables in the model; xisPredicting an output vector for the PV; n is a radical ofsRepresenting a limited number of discrete scenes, NsK actual scenes are obtained from the limited discrete scenes through historical data and are obtained through scene clustering method screening; equation (2) represents all constraints associated with the first stage variables; equation (3) represents the constraint associated with the first stage variable and the second stage variable; equation (4) represents a second order cone relaxation constraint; equation (5) represents the relevant constraint of the second stage variable; equation (6) represents the equality constraint of the photovoltaic power generation uncertainty predicted output.
9. The system for coordination and optimization of the virtual power plant and the power distribution network with the distributed power supplies according to claim 8, wherein the power distribution network intra-day transaction power quantity and the operation cost are obtained by inputting the power distribution network VPP distribution robust coordination and optimization model to a pre-constructed two-stage power distribution network based on multiple discrete scenes, and the system comprises:
and solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multi-discrete scene by adopting a column and constraint generation algorithm to obtain the daily trading electric quantity and the operating cost of the power distribution network with the VPP under the uncertain environment.
10. The system of claim 9, wherein the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenarios is solved by a column and constraint generation algorithm to obtain the daily transaction electric quantity and the operating cost of the power distribution network with the VPP under the uncertain environment, and the system comprises:
decomposing the problem of solving the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes into a main problem and a sub-problem, wherein the main problem provides a lower bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the sub-problem provides an upper bound for the two-stage power distribution network VPP distribution robust coordination optimization model based on the multiple discrete scenes, the upper bound and the lower bound are gradually closed through continuous iteration, when the difference value of the two bounds is smaller than a preset value, the iteration is stopped, an optimal solution is returned, and the power distribution network transaction power quantity and the operation cost in the day with the VPP under an uncertain environment are obtained;
the lower bound of the main question, denoted:
in the formula (I), the compound is shown in the specification,for the probability distribution found by the sub-problem,m is a second-stage variable flexibly adjusted according to the scene, and is the total number of model iterations;
the upper bound of the sub-problem, expressed as:
the subproblem is a max-min bilayer structure, due to the inner layer constraint range YsCompletely unrelated to the outer layer constraint range psi, so that the inner layer min problem is solved in parallel, the worst probability distribution of the outer layer is searched according to the inner layer solving result,
Ψ is a set interval of the scene probability distribution, representing the confidence set bounded by the 1-norm and ∞ -norm:
in the formula, theta1And theta∞To allow maximum deviation of the probability distribution, α1And alpha∞Respectively uncertainty probability confidence under two norm constraint conditions,representing a set of positive real numbers, hsFor intermediate variables of construction, p0Expressing the initial probability, and K expressing the number of actual operation scenes, which is obtained by historical data;
after the main problem and the sub problem are decomposed, the solving steps are as follows:
step 1): setting an initial value, including:
number of iterations m equals 1, belowThe cutoff value L is equal to 0, the upper cutoff value U is equal to + ∞,the superscript m indicates the number of iterations;
step 2): solving a main problem, comprising:
find the optimal solution x*And L(m)*And updating the lower limit value L ═ max { L, L(m)*};
Step 3): solving the result x in the main problem*Solving the subproblems on the basis of the obtained probability distribution of the worst sceneAnd U(m)*And updating the lower bound value U ═ min { U, U ═(m)*};
Step 4): judging whether the upper and lower bound gaps are smaller than the convergence precision, if so, stopping iteration and returning to the optimal solution x*(ii) a If not, updating scene probability distribution in the main problemAnd define new variables in the main problemAnd adding a correlation constraint Ys (m+1);
Step 5): updating m to m +1, and returning to the step 2);
when iteration is terminated, the upper bound value and the lower bound value are unified, the optimal solution in the power distribution network accessed by the virtual power plant at the moment is determined according to the upper bound value and the lower bound value, and the optimal solution comprises the daily transaction electric quantity with the VPP of the power distribution network in an uncertain environmentAnd carrying in the target function minF according to the optimal solution to obtain the running cost.
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