CN111369032B - Poverty-relief photovoltaic distribution point constant volume method - Google Patents
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Abstract
The invention discloses a poverty-relieving photovoltaic distribution point constant volume method, which comprises the following steps: (1) Constructing an upper-layer power distribution network poverty-relieving photovoltaic access model according to typical daily photovoltaic output, photovoltaic access constraint and power grid operation constraint by taking the minimum economic operation net cost, the minimum photovoltaic power generation reduction and the minimum network loss as upper-layer objective functions; (2) Constructing a lower-layer lean village photovoltaic installation amount investment model by taking economic benefits as a lower-layer objective function according to distributed generation marketization constraints and lean village photovoltaic installation amount investment constraints; (3) Approximating the convexity of the non-convex constraint conditions in the two models; (4) And converting the double-layer planning model into a single-layer model for solving, and obtaining the poverty-relieving photovoltaic stationing constant volume access configuration scheme. The problem that the operation efficiency and the overall income of the power grid in the poverty-stricken area are reduced due to the fact that the poverty-stricken photovoltaic power station is randomly connected into the power grid is solved.
Description
Technical Field
The invention belongs to the technical field of new energy power generation configuration, and particularly relates to a lean-alleviation photovoltaic distribution point constant volume method.
Background
The photovoltaic power generation has the characteristics of cleanness, environmental protection, reliable technology, stable income and the like, so that the photovoltaic poverty-supporting project is promoted in poverty-supporting areas, and the photovoltaic poverty-supporting method not only meets the requirements of an accurate poverty-supporting strategy, but also meets the requirements of a national new energy development strategy. However, the blowout type development of the poverty-alleviation photovoltaic also causes huge burden on the power grid of the poverty-alleviation area, and considering the factors that the power distribution network of the poverty-alleviation area is relatively weak, the load capacity is insufficient, dynamic matching with photovoltaic output is not formed, and the like, the problems of voltage out-of-limit, network loss climbing, high difficulty in accommodation and the like caused by the disordered access of a large number of poverty-alleviation photovoltaics affect the operation efficiency and the overall profit of the power grid of the poverty-alleviation area, and the condition that the lowest profit of poverty-alleviation users cannot be ensured even occurs in partial areas.
At present, the access of a poverty-relief photovoltaic power station is generally determined by a power grid company to access a single transformer according to the photovoltaic construction scale and the capacity of an adjacent transformer, and the access scheme does not relate to the overall and village collective income optimal analysis of a power supply line. When photovoltaic installation capacity reaches a certain scale, the scheme of unordered access further aggravates power grid operation risk and reduces the overall income of the project. The following problems exist in the applicability of photovoltaic poverty alleviation: (1) Poverty-alleviation photovoltaic is basically built in poverty-stricken areas, grid structure of a power grid is weak, partial areas even have the transformation targets of expansion planning, dynamic reconstruction, light storage integrated configuration and the like of the grid structure due to the phenomena of 'one country changing and one village changing', the power grid of the poverty-alleviation areas is difficult to reach in a short time, and huge transformation cost exists; (2) The poverty-relief photovoltaic access power distribution network needs to comply with a series of policy specifications in actual engineering, but most of research only considers the physical constraints of power grid access, so that the referential significance to actual engineering operation is not great; (3) In the access of the poverty-relieving photovoltaic, a plurality of benefit subjects such as poverty-relieving regional village groups are still involved except for a power grid company, different typical trading modes of distributed power generation marketization have different influences on the benefit relations among the subjects, and the distributed power generation marketization is rarely involved in the research.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a poverty-relieving photovoltaic distribution point constant volume method, and aims to solve the problem that a poverty-relieving photovoltaic power station is randomly connected to a power grid at the present stage.
In order to realize the purpose, the invention provides a poverty-relieving photovoltaic distribution point constant volume method which comprises the following steps:
the method comprises the following steps:
(1) Constructing an upper-layer powr distribution network poverty-alleviation photovoltaic access model by taking the minimum economic operation net cost, the minimum photovoltaic power generation reduction and the minimum network loss as upper-layer objective functions according to typical daily photovoltaic output, photovoltaic access constraint conditions and power grid operation constraint conditions;
(2) Constructing a lower-layer lean village photovoltaic installation amount investment model by taking economic benefits as a lower-layer objective function according to a distributed generation marketization constraint condition and a lean village photovoltaic installation amount investment constraint condition;
(3) Convex relaxation is carried out on the non-convex constraint conditions in the two models;
(4) Converting the photovoltaic installation amount investment model of the lower-layer poverty-depleted village into an upper-layer constraint condition, and realizing the solution of converting a double-layer planning model into a single-layer model;
(5) And obtaining a poverty-relief photovoltaic stationing constant volume access configuration scheme.
Preferably, the method for converting the photovoltaic installation amount investment model of the lower-layer poverty-depleted village into the upper-layer constraint condition is a KKT condition conversion method;
preferably, the photovoltaic output formula is:
wherein, P s Rated for the photovoltaic power supply, alpha T Is the power temperature coefficient of the photovoltaic panel, T is the operating photovoltaic module temperature,
is latitude of
Photovoltaic region to be builtThe average value of the surface solar irradiance in hours of m, month, d days and h;
the average hourly value formula of the surface solar irradiance of the photovoltaic region to be built is as follows:
wherein the content of the first and second substances,
as the latitude
The sunshine clear sky index of the mth month of the photovoltaic region to be built; alpha is alpha p (m) is the meteorological attenuation coefficient for month m;
as a latitude of
The total amount of extraterrestrial single-day solar irradiation of the mth month and the day d of the photovoltaic region to be built; k t (h) The daily variation coefficient of the solar irradiance on the earth surface;
wherein, I 0 Is the base value of solar irradiance in W/m 2 ；
The latitude of the area to be built; delta is the declination angle;
is the hour angle of the daily rise; n is the sequence number of the calculation day in the whole year; h is a total of sr The daily rise time; h is ss Is the sunset time; alpha is the direct solar latitude on the Nth day; Δ t m Is a time correction factor;
preferably, the upper layer objective function included in the upper layer power distribution network poverty-leaned photovoltaic access model is as follows:
a. economic net cost minimum objective function:
Obj 1 ＝C zb +C pvbuy +C sjbuy -B sjsell -B load -B gwf
wherein, obj 1 For economic net cost of operation, C zb Annual cost for installing special transformers, C pvbuy Acquisition costs for grid companies for photovoltaic power generation, C sjbuy Annual cost of electricity purchase from grid company to higher level grid, B sjsell Annual electricity sales revenue for grid companies to higher levels of the grid, B load Annual electricity sales revenue for grid companies to loads in the electricity supply area, B gwf The method comprises the following steps of (1) collectively collecting net-passing fee profits from all villages for a power grid company in a distributed power generation marketization mode;
wherein, C zbprice,k,i The additional cost of different capacity special changes in the ith village is defined as r is the discount rate and T gc For engineering period, α 0 Is the residual value rate of the equipment, P byqzb,i Collectively adding special photovoltaic access capacity, C, to ith village cl Is a village collective set; lambda rmbg For electricity prices on the coal-burning pole, W bg,i The photovoltaic power generation quantity is collectively purchased in the ith village by a power grid company; lambda vsjlevel For transmission and distribution rates, W, of the voltage class at which the grid company is connected to the superordinate grid sjbuy The annual total electric quantity purchased from a power grid company to a superior power grid; w sjsell For the grid company to the superordinate gridAnnual total electricity sold; lambda ny For electricity price for agricultural production, W loadsum Total annual load for the power supply area of the grid company, W zjload The annual transaction total electric quantity of a direct transaction contract is signed for the village group and the power consumer; lambda [ alpha ] clv,i Collectively establishing power transmission and distribution prices (considering 400V or 10kV access) corresponding to the access voltage grade of the photovoltaic power station for the ith village, and determining lambda clvmax,i The transmission and distribution price of the highest voltage level involved in the ith village collective distributed generation marketization trade, W sum,i Collectively building the annual total power generation of the power station for the ith village;
b. minimum objective function of photovoltaic power generation reduction:
wherein, obj 2 For the reduction of photovoltaic power generation, tjs is the number of time slots, P pv,t For the unit power output value of the photovoltaic panel in the t-th calculation period, byq is a 10kV/400V public transformer (hereinafter referred to as "public transformer") set of the power grid of the area to be planned, P byq,i For the photovoltaic access capacity, P, of the ith utility transformer byqzb,i Collectively adding special photovoltaic access capacity, P, of village i byq10,i Photovoltaic capacity, T of 35kV/10kV transformer connected to ith village ts,t The number of the same time periods which are represented by the tth calculation time period and run all year round, G is the actual access node set of the photovoltaic power station, and P g,i,t For the ith node, a force value, W, is derived at the t-th calculation period sjbuy Annual total quantity of electricity, W, purchased from a grid company to a superordinate grid sjsell Annual total electric quantity sold to a superior power grid for a power grid company;
c. network loss minimum objective function:
wherein, obj 3 For the amount of loss of the network, W sjbuy Annual power purchase from a grid company to a superordinate gridTotal quantity of electricity, C cl As a collective set of villages, W sum,i Collectively commissioning the annual total power generation of the power station, W, for the ith village sjsell Annual total electricity quantity, W, sold to a superordinate grid for a grid company loadsum The total annual load of a power supply area of a power grid company is supplied;
preferably, the objective function of the photovoltaic installation amount investment model of the lower-layer poverty-depleted villages is an economic income objective function:
Obj i ＝C pv,i +C interest,i +C yw,i +C wire,i +C gwf,i -B pv,sell,i -B pv,bt,i i∈Ccl
wherein, obj i Net cost of building a photovoltaic for the ith village, C gwf,i The net charge paid to the grid company by the photovoltaic power station built for the village in year, B pv,sell,i For electricity sales income of ith village in each transaction mode, C gwf,i ，B pv,sell,i Determined by distributed power generation marketization constraints;
wherein, C pv,i Annual cost for photovoltaic installation, P fp,i ，P pt,i Determining the poverty-alleviation photovoltaic capacity and the common distributed photovoltaic capacity for the ith village respectively, wherein r is the coverage rate and T gc For engineering period, α 0 Is the residual value rate of the equipment, C pv,inv The installation cost of the unit power photovoltaic; c interest,i Loan interest for the commissioning of ordinary photovoltaics, rate is loan interest rate, C yw,i For the operation and maintenance costs of a photovoltaic power generation project, λ yw For electric power operation and maintenance fee, W sum,i Collectively building annual total power generation of power station for ith village, C wire,i Overhead costs for photovoltaic plant access, C w Is the unit price of the wire gf,i,k Distance, dis, for photovoltaic power plant and kth common transformer gf10,i Distance of a 35kV/10kV transformer of a photovoltaic power station, B pv,bt,i Is subsidized for the photovoltaic power generation electric quantity received all year round, lambda btfp For relieving povertyVolt-degree electric patch, lambda btpt Is a common photovoltaic power subsidy, ratio i The percentage of poverty-relief photovoltaic in photovoltaic power stations built for villages;
preferably, the non-convex constraint influence model included in the upper distribution network poverty alleviation photovoltaic access model is a power flow equation constraint:
P ij ＝g ij V i 2 -g ij V i V j cosθ ij +b ij V i V j sinθ ij
Q ij ＝b ij V i 2 -g ij V i V j sinθ ij -b ij V i V j cosθ ij
the flow equation constrains the convex approximation of the non-convex model:
P ij ＝g ij U i -g ij W ij +b ij T ij
Q ij ＝b ij U i -g ij W ij -b ij T ij
wherein, P ij For branch active power, Q ij Is the branch reactive power, g ij For branch conductance, b ij For branch susceptance, V i And V j Node voltages, θ, at node i and node j, respectively ij Representing the difference of voltage phase angles at two ends of the branch;
preferably, the non-convex constraint influence model included in the lower-layer poverty-induced village photovoltaic installation quantity investment model is as follows:
ratio i ＝P fp,i /(P fp,i +P pt,i )
wherein, ratio i Poverty-relief photovoltaic proportion, P, in photovoltaic power station built for villages fp,i 、P pt,i Determining the built poverty-alleviation photovoltaic capacity and the common distributed photovoltaic capacity for the ith village respectively;
the convexity is approximated as:
or
a＝0.005Pkh i
b＝0.007Pkh i
x 1 ＝P fp,i
x 2 ＝P pt,i
x s ＝x 1 +x 2
wherein Pkh i Number of impoverished households for village, P fp,i ，P pt,i And determining the built poverty-alleviation photovoltaic capacity and the common distributed photovoltaic capacity for the ith village respectively.
Through the technical scheme, compared with the prior art, the invention has the following beneficial effects:
1. the method comprises the steps that a poverty-relief photovoltaic access model of an upper-layer power distribution network is built, the model can meet different target requirements of the power distribution network, poverty-relief photovoltaic access constraint conditions and power grid operation constraint conditions are considered, and actual engineering requirements are met;
2. establishing a photovoltaic installation quantity investment model of the lower-layer poverty-stricken villages, wherein the model can meet the target requirement of collective economic benefit maximization of all villages in poverty-stricken areas, and can better reflect the actual investment behavior of the poverty-stricken villages by considering poverty-stricken photovoltaic investment policy constraints and distributed generation marketization environment constraints;
3. the poverty-reduced photovoltaic distribution point constant volume double-layer model established based on the power distribution network poverty-reduced photovoltaic access model and the poverty-reduced village photovoltaic installation volume investment model can realize approximate convexity of a non-convex model by using a convex relaxation technology, and a KKT condition conversion method is adopted to convert a double-layer planning model into a single-layer model for solving, so that a complex programming process and longer optimization time during solving by using a simulation method are omitted, and the method is simpler and faster.
Drawings
FIG. 1 is a flow chart of a lean-alleviation photovoltaic stationing and sizing method provided by the invention;
FIG. 2 is a functional diagram illustrating the transformation of a non-convex constraint impact model into a convex approximation provided by the present invention;
FIG. 3 is a comparison graph of net profit for each subject under three different scenarios provided in this example;
FIG. 4 is a graph comparing photovoltaic installation capacity under three different schemes provided by the present embodiment;
fig. 5 shows the operation index of each photovoltaic power station under three different schemes provided by this embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
As shown in fig. 1, the invention provides a lean-quenching photovoltaic distribution point constant volume method:
s1, calculating photovoltaic output accounting for small-scale fluctuation of the photovoltaic output according to a solar irradiance theory, and selecting a typical day with rural load characteristics;
the photovoltaic output formula for a typical day is:
wherein, P s Rated for the photovoltaic power supply, alpha T Is the power temperature coefficient of the photovoltaic panel, T is the operating photovoltaic module temperature,
as a latitude of
The average value of the surface solar irradiance of the photovoltaic region to be built in the mth month, d days and h;
according to the ground surface solar irradiance theory of the photovoltaic region to be built, the hourly mean value formula of the ground surface solar irradiance of the photovoltaic region to be built is as follows:
in the formula (I), the compound is shown in the specification,
as a latitude of
The sunshine clear sky index of the mth month of the photovoltaic region to be built can be obtained by querying a NASA database; alpha is alpha p (m) is m The meteorological attenuation coefficient of the month is obtained according to the historical data statistics of the photovoltaic region to be built;
as a latitude of
The total amount of extraterrestrial single-day solar irradiation of the mth month and the day d of the photovoltaic region to be built; k t (h) The daily variation coefficient of the solar irradiance on the earth surface;
wherein:
wherein, I 0 Is the base value of solar irradiance and has the unit of W/m 2 ；
The latitude of the area to be built; delta is declination angle;
is the hour angle at daytime; n is the sequence number of the calculation day in the whole year; h is a total of sr The daily rise time; h is ss Is the sunset time; alpha is the Nth day direct solar radiation latitude; Δ t m The time correction coefficient is the time correction coefficient, namely the time zone serial number adopted by the time at that time is subtracted by the time zone serial number corresponding to the local longitude;
considering the influence of weather characteristics and space-time characteristics on photovoltaic output characteristics and the characteristics of peak load, busy load, perennial load and the like of rural loads, a typical day method is adopted, three typical days of cloudy days, sunny days and rainy days are respectively selected as representatives every month in the whole year, 24 time periods are taken every day, and a photovoltaic output model is calculated in 864 time periods in total;
s2: constructing an upper-layer powr distribution network poverty-alleviation photovoltaic access model by taking the minimum economic operation net cost, the minimum photovoltaic power generation reduction and the minimum network loss as upper-layer objective functions according to typical daily photovoltaic output, photovoltaic access constraint conditions and power grid operation constraint conditions;
(2.1) three types of upper layer objective functions of the poverty-leaned photovoltaic access model of the power distribution network:
A. the net cost of economic operation minimum objective function is:
Obj 1 ＝C zb +C pvbuy +C sjbuy -B sjsell -B load -B gwf (1)
wherein, obj 1 For economic net cost of operation, C zb Annual cost for installing special transformer (hereinafter referred to as "special transformer"), (C) pvbuy Acquisition costs for grid companies for photovoltaic power generation, C sjbuy Annual purchase costs for the grid company to the higher-level grid, B sjsell Annual revenue for the grid company to sell to the higher level grid, B load Annual revenue generation for grid companies in the supply area gwf The method comprises the following steps of (1) collectively collecting network fee profits from all villages for a power grid company in a distributed power generation marketization mode;
wherein, C zbprice,k,i The adding cost of different capacity exclusive changes is set in the ith village, r is the discount rate and T gc For engineering period, α 0 Is the residual rate of the device, P byqzb,i Collectively adding special photovoltaic access capacity, C, to ith village cl Is a village collective set; lambda [ alpha ] rmbg For electricity prices on the coal-burning pole, W bg,i The photovoltaic power generation quantity is collectively purchased in the ith village for a power grid company; lambda [ alpha ] vsjlevel For transmission and distribution rates, W, of the voltage class at which the grid company is connected to the superordinate grid sjbuy The annual total electric quantity of the power purchased from the power grid company to the superior power grid; w sjsell Annual total electric quantity sold to a superior power grid for a power grid company; lambda [ alpha ] ny For electricity price for agricultural production, W loadsum Total annual load for the power supply area of the grid company, W zjload The total annual transaction electric quantity of the direct transaction contract is signed for the village group and the power consumer; lambda [ alpha ] clv,i The power transmission and distribution price corresponding to the access voltage grade of the photovoltaic power station is collectively built for the ith village, and 400V or 10kV access and lambda are generally considered clvmax,i The transmission and distribution price of the highest voltage level involved in the ith village collective distributed generation marketization trade, W sum,i Collectively building the annual total power generation of the power station for the ith village;
B. the minimum objective function of the reduction of the photovoltaic power generation is as follows:
wherein, obj 2 For the reduction of photovoltaic power generation, tjs is the number of time slots, P pv,t For the unit power output value of the photovoltaic panel in the tth calculation time period, byq is a 10kV/400V public transformer (hereinafter referred to as "public transformer") set of the power grid of the area to be planned, P byq,i For the photovoltaic access capacity, P, of the ith utility transformer byqzb,i Adding photovoltaic access capacity P of special transformer to ith village collectively byq10,i Photovoltaic capacity, T of 35kV/10kV transformer connected to ith village ts,t The number of the same time periods which are represented by the tth calculation time period and run all year round, G is the actual access node set of the photovoltaic power station, and P g,i,t For the ith node, a force value, W, is derived at the t-th calculation period sjbuy Annual total quantity of electricity, W, purchased from a grid company to a superordinate grid sjsell Annual total electric quantity sold to a superior power grid for a power grid company;
C. the network loss minimum objective function is:
wherein, obj 3 As the amount of grid network loss, W sjbuy Annual total quantity of electricity, C, to a superordinate grid for a grid company cl As a collective set of villages, W sum,i Collectively commissioning the annual total power generation of the power station for the ith village, W sjsell Annual total electricity quantity, W, sold to a superordinate grid for a grid company loadsum The annual total load of a power supply area of a power grid company is supplied;
(2.2) the constraint conditions of the poverty-alleviation photovoltaic access model of the power distribution network comprise typical daily photovoltaic output, photovoltaic access constraint conditions and power grid operation constraint conditions; the following constraints are specifically adopted for characterization by combining three constraint conditions:
A. and (3) power generation node constraint:
a. restriction of electricity purchase and sale
Wherein, P g,sjbuy,t ，P g,sjsell,t The power purchasing power and the power selling power of a power grid company to a superior power grid in the tth time period are respectively; y is sjbuy,t ，Y sjsell,t Zone bits for purchasing and selling electricity respectively in the t-th time period; the formula (5) ensures that only one state, P, exists for electricity purchase and electricity sale in the same time period g,sjbuy,max ，P g,sjsell,max The maximum values of the electricity purchasing power and the electricity selling power are respectively;
b. photovoltaic power generation node constraints
Wherein, P g,i,t For the ith node, a force value, P, is derived at the t-th calculation period pv,t For the unit power output value, P, of the photovoltaic panel in the t-th calculation period byq,i For the photovoltaic access capacity of the ith public transformer, byq is a 10kV/400V public transformer set of the power grid of the area to be planned, P byqzb,i Adding photovoltaic access capacity P of special transformer to ith village collectively byq10,i The photovoltaic capacity of a 35kV/10kV transformer is accessed into the ith village, czb is a special transformer additional node set, C 10 The photovoltaic access node set is of a 10kV voltage class;
B. and (3) restricting the access capacity of the transformer:
according to the relevant regulations of 'typical design of network connection engineering for distributed photovoltaic poverty alleviation project of national grid company', poverty alleviation photovoltaic mainly has three access modes: the method comprises the following steps of low-voltage public power grid household access, low-voltage special line access (public transformer access) of a transformer on a public post and concentrated access (special transformer access) of a transformer on a special post; for the purpose of unified management, the poverty-relieving photovoltaic is mostly constructed in a centralized manner in the actual engineering; therefore, the access mode related to the method does not comprise a household poverty-relieving photovoltaic mode of household access of the low-voltage public power grid;
a. public transformer access constraints
Wherein, P byq,i For the photovoltaic access capacity, P, of the ith utility transformer byqrl,i ，Y byq,i For the installation capacity and the access flag of the ith transformer, byq is a 10kV/400V public variable set of a power grid of an area to be planned, public variable access is selected when the general photovoltaic access capacity is 20 kW-200 kW, and the public variable capacity needs to be 1.1-1.2 times of the photovoltaic access capacity;
b. special variable access constraints
Wherein i ∈ Ccl, Y byqzb,i,100 ，Y byqzb,i,200 ，Y byqzb,i,400 Respectively installing zone bits of different types of transformers for ith village, P byqzb,i,100 ，P byqzb,i,200 ，P byqzb,i,400 Photovoltaic power station access capacity P when different types of transformers are additionally arranged for ith village byqzb,i Photovoltaic access capacity of the special transformer is added to the ith village collectively, and the formula (8) ensures that 1 special transformer is installed at most in each village; generally, when the photovoltaic access capacity is 80 kW-400 kW, special variable centralized access is selected, a transformer with the capacity of 100, 200 or 400kVA can be additionally installed, and the special variable capacity needs to be 1.1-1.2 times of the installed capacity of the photovoltaic;
c.35kV/10kV transformer access restraint
Considering that a research area is a rural weak power distribution network, and the power networks connected with each village are mostly 10kV buses, so that the highest access voltage grade of the photovoltaic power station is 10kV;
0.4Y byq10,i ≤P byq10,i ≤6Y byq10,i i∈Ccl (9)
wherein, P byq10,i Photovoltaic capacity, Y of 35kV/10kV transformer connected to ith village byq10,i Connecting a 10kV voltage level zone bit for the ith village photovoltaic power station; the national grid company 'distributed power supply access distribution network related specifications' requires that the maximum 10kV voltage class access capacity is 6MW;
C. photovoltaic access total amount constraint:
wherein, P fp,i ，P pt,i The poverty-alleviation photovoltaic capacity and the common distributed photovoltaic capacity which are put into operation are respectively determined for the ith village, and are decision variables P of the village collective side investment model byq,i For the photovoltaic access capacity of the ith public transformer, byq is a 10kV/400V public transformer set of a power grid of a region to be planned, P byqzb,i Adding photovoltaic access capacity P of special transformer to ith village collectively byq10,i Photovoltaic capacity, cl of 35kV/10kV transformer connected to ith village byq,i The node set of the transformer which can be accessed by photovoltaic is put into operation in the ith village;
D. and (4) electric quantity sum constraint:
wherein Tjs is used for calculating the number of time periods, P g,k,t For the kth node, a force value, P, is derived at the t-th calculation time period gzb,k,i,t The active power output P of the photovoltaic accessed by the special transformer in the ith village in the kth node in the tth calculation period g10,k,i,t The active power output of the photovoltaic connected to the ith village in the kth 10kV voltage level node in the tth calculation period is T ts,t The same number of time periods, W, for the year-round operation represented by the tth calculation period sjbuy Annual total quantity of electricity, W, purchased from a grid company to a superordinate grid sjsell Annual total quantity of electricity sold to a superordinate grid for a grid company, P g,sjbuy,t ，P g,sjsell,t The power purchasing power and the power selling power of a power grid company to a superior power grid in the tth time period are respectively;
E. other constraints are:
besides the constraints, the power grid company model still needs to consider the constraint conditions such as power flow equation constraint, node balance constraint, reactive power constraint, node voltage constraint, power flow out-of-limit constraint, line current constraint and the like, and the specific form is as follows:
wherein, P ij For branch active power, Q ij Is the branch reactive power, g ij For branch conductance, b ij For branch susceptance, V i And V j Node voltages, θ, at node i and node j, respectively ij Representing the difference between the phase angles of the voltages at the two ends of the branch, [ pi ] (i) representing all the nodes connected to node i, P gi Representing the amount of generated photovoltaic power, P, installed at node i di Representing the amount of active load at node i. Q gi Represents the installation of photovoltaic reactive power generation capacity and reactive compensation capacity, Q, of reactive equipment at the node i di Representing the amount of reactive load at node i,
representing line capacity, I max Allowing maximum current for the line;
s3: constructing a lower-layer lean village photovoltaic installation amount investment model by taking economic benefits as a lower-layer objective function according to a distributed generation marketization constraint condition and a lean village photovoltaic installation amount investment constraint condition;
(3.1) a lower-layer objective function of the photovoltaic installation amount investment model of the poverty-induced villages:
and taking the villages in the poverty-alleviation area as independent benefit subjects collectively, and making a decision according to respective benefit maximization targets.
Obj i ＝C pv,i +C interest,i +C yw,i +C wire,i +C gwf,i -B pv,sell,i -B pv,bt,i i∈Ccl (13)
Wherein, obj i Net cost of building a photovoltaic for the ith village, P fp,i ，P pt,i Respectively determine the ith villageBuilt poverty-alleviation photovoltaic capacity and common distributed photovoltaic capacity, C gwf,i The net charge paid to the grid company by the photovoltaic power station built for the village in year, B pv,sell,i Earnings for selling electricity in ith village under each trading mode, C gwf,i ，B pv,sell,i Determined by distributed power generation marketization constraints;
wherein, C pv,i Annual cost for photovoltaic installation, r is the rate of occurrence, T gc For engineering period, α 0 Is the residual value rate of the equipment, C pv,inv The installation cost of the unit power photovoltaic; c interest,i Loan interest for setting common photovoltaic, unconscious loan provided by the nation for poverty-alleviation photovoltaic, rate is loan interest rate, C yw,i For the operation and maintenance costs of a photovoltaic power generation project, λ yw Maintenance fee for electric power, W sum,i Collectively building the annual total power generation of the power station for the ith village; c wire,i Overhead costs for photovoltaic plant access, C w Is the unit price of the wire gf,i,k Distance, dis, for the photovoltaic plant and the kth common variable gf10,i The distance is the distance of a 35kV/10kV transformer of a photovoltaic power station; b is pv,bt,i Is subsidized for the photovoltaic power generation electric quantity received all year round, lambda btfp For photovoltaic power subsidy for poverty relief, lambda btpt Is a common photovoltaic power subsidy, ratio i The percentage of poverty-reduced photovoltaic in photovoltaic power stations built in villages, that is,
ratio i ＝P fp,i /(P fp,i +P pt,i ) (15)
(3.2) constraint conditions of the photovoltaic installation amount investment model of the non-smooth villages:
A. putting into construction scale constraint:
wherein Pkh i Number of impoverished households for village, P area,i The maximum photovoltaic capacity that can be built for the unused land in the village. According to the regulation of photovoltaic poverty-relief power station management method, the scale of the village-level poverty-relief power station is configured according to the number of helped poverty-relief households about 5kW per household, the maximum is not more than 7kW, the scale of a single power station is not more than 300kW in principle, and the conditions of nearby access and consumption can be widened to 500kW;
B. and (3) yield constraint:
Obj i /Pkh i ≤-3000 (17)
according to relevant regulations, photovoltaic poverty alleviation needs to ensure that each household of poverty-stricken increases income by more than 3000 yuan every year.
(3.3) marketization constraint of distributed generation
A. Transaction pattern constraints
a. Direct transaction mode constraints:
wherein λ is xy,i Agreement electricity price, W, for direct transaction between photovoltaic power generation project and electricity consumer built in village zjload Total annual transaction power, ccl, for the village group to sign a direct transaction contract with the electricity consumers zj A set of villages that employ a direct transaction mode;
b. and (3) power grid electricity-substituted selling mode constraint:
B pv,sell,i ＝λ zh W sum,i i∈Ccl ds (19)
wherein λ is zh For the comprehensive electricity selling price of the power grid enterprise, the Ccl is limited by the load electricity selling condition of the power supply area to be researched ds A village set adopting a power grid electricity-substituted selling mode;
c. the power grid pole surfing electricity price purchasing mode comprises the following steps:
B pv,sell,i ＝λ rmbg W sum,i i∈Ccl bg (20)
in the formula of lambda rmbg Ccl for the electricity price of coal-burning marker post bg Is a village set adopting a post internet surfing electricity price mode.
B. Over-the-net cost constraint
In distributed power generation marketization, village groups in a direct transaction mode and a power grid electricity-substitute selling mode need to pay network charge to a power grid enterprise, village groups in a power grid pole internet-surfing electricity price purchasing mode do not need to pay network charge, but the power grid enterprise needs to bear corresponding network charge loss;
C gwf,i ＝-B gwf,i ＝(λ clv,i -λ clvmax,i )W sum,i ,i∈(Ccl zj &Ccl ds ) (21)
wherein, C gwf,i The net charge paid by the photovoltaic power station put into operation for villages to the power grid company by year, B gwf The method is characterized in that the method is used for collectively collecting the net-passing fee income, lambda, from each village under the distributed power generation marketization mode by a power grid company clv,i Collectively establishing power transmission and distribution price, lambda, corresponding to the access voltage grade of the photovoltaic power station for the ith village clvmax,i Transmission and distribution price, W, of the highest voltage level involved for ith village collective distributed power generation marketization trade sum,i Collectively commissioning the annual total power generation capacity, ccl, of the power station for the ith village zj Ccl for a set of villages using direct transaction mode ds Ccl for a village set using a power grid electricity-vending model bg Is a village set adopting a post internet-surfing electricity price mode;
wherein, P fp,i ，P pt,i Determine the poverty-relieving photovoltaic capacity and the common distributed photovoltaic capacity, lambda, to be put into operation for the ith village respectively clv,i Collectively establishing power transmission and distribution prices (considering 400V or 10kV access) corresponding to the access voltage grade of the photovoltaic power station for the ith village, and determining lambda clvmax,i The transmission and distribution price of the highest voltage level involved in the ith village collective distributed generation marketization trade is lambda 1 、λ 10 And λ 35 Respectively less than 1kV, 1-10 kV and 35kV,
the annual average power load in the ith village,
annual average power load on the whole power supply area;
and the grid charge standard is determined in a grading way according to the access voltage grade and the transmission and power consumption range. When the photovoltaic installation capacity is smaller than the annual average power load in the power supply area, the consumption of the electric quantity of the project in the voltage class range can be determined, the 'power grid fee' standard in the voltage class is executed, and the power grid fee standard of the voltage class at the upper stage is executed when the power grid fee standard exceeds the power grid fee standard of the voltage class at the lower stage;
to sum up, the poverty alleviation photovoltaic access model of the upper-layer power distribution network is as follows:
the photovoltaic installation amount investment model of the lower-layer poverty-induced village is as follows:
s4: the non-convex constraint conditions contained in the upper-layer poverty-relief photovoltaic access model and the lower-layer poverty-relief village photovoltaic installation amount investment model realize the convex approximation of the non-convex model by using a convex relaxation technology;
in the poverty-relief photovoltaic stationing and volume-fixing double-layer model, two non-convex constraint influence models are solved, wherein the two non-convex constraint influence models are in a trend equation constraint mode in an upper-layer power distribution network company model, and the formula (15) is in a lower-layer poverty-relief village photovoltaic installation volume decision model;
(4.1) convex relaxation of tidal flow equation constraints
Defining:
U i ＝V i 2
W ij ＝V i V j cosθ ij
T ij ＝V i V j sinθ ij
the power flow equation can be transformed into:
P ij ＝g ij U i -g ij W ij +b ij T ij
Q ij ＝b ij U i -g ij W ij -b ij T ij
the node voltage constraint can be transformed into:
further relaxation is inequality:
the power flow constraint sum equation (26) is converted into a 2-norm form, i.e., a standard second order cone equation is available:
(4.2) convex relaxation of lower layer model
Let x 1 ＝P fp,i ,x 2 ＝P pt,i ,x s ＝x 1 +x 2 Equation (25) can be abstracted as a model:
wherein the content of the first and second substances,
a＝0.005Pkh i
b＝0.007Pkh i
c＝P area,i
d＝3000
equation (27) is fully equivalent to equation (25), with formally two additional decision variables, ratio and x s Equation (15) is replaced by the constraints (d) and (e) of equation (27), and equation (27) is still a non-convex model due to the existence of constraint (e). Further, as shown in fig. 2, the constraint (e) can be regarded as a mathematical form of z = xy, which is a conical surface in three-dimensional space, such as the light-colored surface in fig. 2, and x is obtained by using a convex relaxation technique 1 ＝x s ratio relaxation, realizing a convex hull form formed by two intersecting planes, such as a dark color plane in fig. 2, wherein a specific alternative form of constraint (e) is as follows:
or
s5: converting the photovoltaic installation amount investment model of the low-layer poverty village into an upper-layer constraint condition by adopting a KKT condition conversion method, and realizing the solution of converting a double-layer planning model into a single-layer model;
the method adopts KKT condition to convert a lower layer model (25) into an upper layer constraint condition, and converts the whole problem into mixed integer nonlinear programming through constraint linearization;
original feasible field:
in the formula of 1 ～μ 10 Are dual variables.
Dual variable feasible field:
μ i ≥0 i∈[1,9] (29)
complementary relaxation conditions:
μ 1 (a-x 1 )＝0μ 2 (x 1 -b)＝0
μ 3 x 2 ＝0
μ 4 (a-x s )＝0μ 5 (x s -c)＝0
μ 7 (a/c-ratio)＝0μ 8 (ratio-b/a)＝0
μ 9 [d+f(x 1 ,x 2 ,x s ,ratio)]＝0
stability conditions:
the complementary relaxation conditions have strong nonlinearity, and the linearization treatment can be obtained by setting the maximum number:
in the formula (I), the compound is shown in the specification,
is a binary variable flag bit, and M is a maximum number;
the lower layer model is converted into constraint conditions (28), (29), (30) and (31) through KKT conditions, the four constraint conditions are combined into the upper layer model to obtain a single layer model, and therefore the whole model is converted into a mixed integer nonlinear programming problem and can be solved by using mature mathematical programming software.
In conclusion, the poverty-alleviation photovoltaic distribution point constant volume double-layer model is established under the distributed power generation marketization environment by fully considering poverty-alleviation photovoltaic access policies and standard constraints and considering the commissioning behaviors of benefit subjects such as poverty-alleviation village groups on the premise of avoiding large-scale modification of a power distribution network.
The practical distribution network system of a certain village and town is taken as an embodiment. The main line of the power grid in the area to be planned is a 10kV outgoing line, and 12 10kV/400V transformers are provided in total, wherein 2 transformers are special load transformers; the total length of the trunk line is 8.51km, the annual maximum load is 0.714MW, and the ultimate transmission capacity is 4.05MW; the whole line relates to three administrative villages A, B and C. Under the distributed power generation marketization environment, a power grid pole-surfing electricity price purchasing mode is adopted in village A, a power grid electricity selling mode is adopted in village B, and a direct trading mode is adopted in village C. Table 1 provides the village parameters used in this embodiment, table 2 provides the key economic parameters and table 3 with the basic line parameters, which are specifically as follows:
TABLE 1 village parameters
TABLE 2 Key economic parameters
| Poverty-relief photovoltaic patch | 480 yuan/MWh |
| Ordinary photovoltaic subsidy | 330 yuan/MWh |
| Coal burning pole for electric price | 369.3 Yuan/MWh |
| Comprehensive electricity price | 608.6 yuan/MWh |
| Agreement price of electricity | 700 yuan/MWh |
| Less than 1kV transmission and distribution price | 349 member/MWh |
| 1kV to 10kV transmission and distribution electrovalence | 315 element/MWh |
| Over 35kV power transmission and distribution price | 282 Yuan/MWh |
| General agricultural electricity price | 484.2 element/MWh |
| Photovoltaic operation and maintenance cost | 100 yuan/MWh |
| Photovoltaic installation cost | 7000 yuan/kW |
| Installation cost of 100kw special transformer | 40500 yuan |
| 200kw installation cost for special transformer | 81000 yuan |
| Installation cost of 400kw special transformer | 162000 yuan |
| Current rate of sticking | 0.03 |
| Bank loan interest rate | 0.05 |
| Residual value rate | 0.05 |
| Engineering period | 20 years old |
TABLE 3 line parameters
In this embodiment, with the minimum net cost of economic operation as a target, 3 different access schemes are set to analyze the effectiveness of the present invention:
in the scheme 1, only poverty-alleviation photovoltaic access is allowed, and a photovoltaic power station is integrally connected to a single transformer to operate;
according to the scheme 2, poverty-alleviation photovoltaic and common photovoltaic are allowed to be accessed simultaneously, and a photovoltaic power station is integrally accessed to a single transformer to operate;
scheme 3 allows poverty-relieving photovoltaic and common photovoltaic to be accessed simultaneously, and adopts a stationing constant-volume double-layer model for access.
Respectively carrying out comparative analysis on three aspects of main body net income, photovoltaic installation amount and each operation index of the power grid under the implementation of the scheme in the step 3 according to the graph 3, the graph 4 and the graph 5;
in the aspect of economic benefit shown in fig. 3, the scheme 2 can further increase the total benefit of the poverty-relieving users in the situation of reducing the loss of the power grid company compared with the scheme 1; on the basis, the loss can be further reduced and the income can be further increased by adopting the scheme 3 for access.
In terms of operation of the power grid shown in fig. 4 and 5, each access scheme performs basically the same in three aspects of photovoltaic reduction, grid loss and power purchase to the upper-level power grid, and is at a better level. On the other hand, the optimal photovoltaic installation amount which can be accommodated by the three schemes is relatively different, and the advantage of the scheme 3 is more obvious in view of a large amount of photovoltaic which exists in a weak power distribution network in the poor area at present.
In conclusion, compared with the traditional access scheme, the poverty-relieving photovoltaic stationing and constant-volume double-layer access scheme provided by the invention can improve economic benefits of poverty-relieving villages and reduce economic losses of power grid companies, can effectively reduce running risks of the power grid, improves photovoltaic admission scale and achieves the aim of 'win and win' at one stroke.
It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.
Claims (4)
1. A poverty-relieving photovoltaic distribution point constant volume method is characterized by comprising the following steps:
(1) Constructing an upper-layer power distribution network poverty-alleviation photovoltaic access model according to typical daily photovoltaic output, photovoltaic access constraint conditions and power grid operation constraint conditions by taking the minimum net cost of economic operation, the minimum reduction of photovoltaic power generation and the minimum network loss as upper-layer objective functions;
the typical solar photovoltaic output formula is:
wherein, P s Rated for the photovoltaic power supply, alpha T Is the power temperature coefficient of the photovoltaic panel, T is the operating photovoltaic module temperature,
as a latitude of
The average value of the surface solar irradiance hour of the photovoltaic region to be built at the mth month, d days and h;
the average hourly value formula of the surface solar irradiance of the photovoltaic region to be built is as follows:
wherein the content of the first and second substances,
as the latitude
The sunshine clear sky index of the mth month of the photovoltaic region to be built; alpha is alpha p (m) is the meteorological attenuation coefficient in the mth month;
as a latitude of
The total amount of extraterrestrial single-day solar irradiation of the mth month and the day d of the photovoltaic region to be built; k t (h) The daily change coefficient of the surface solar irradiance is obtained;
wherein, I 0 Is the base value of solar irradiance in W/m 2 ；
The latitude of the area to be built; delta is declination angle;
is the hour angle at daytime; n is the calculation dayThe number of sequences in the year; h is sr The daily rise time; h is ss Is the sunset time; alpha is the direct solar latitude on the Nth day; Δ t m Is a time correction factor;
the expression of an upper layer objective function in the upper layer power distribution network poverty alleviation photovoltaic access model is as follows:
a. economic net cost minimum objective function:
Qbj 1 ＝C zb +C pvbuy +C sjbuy -B sjsell -B load -B gwf
wherein Qbj 1 For economic net cost of operation, C zb Annual cost of adding special transformers, C pvbuy Acquisition costs for grid companies for photovoltaic power generation, C sjbuy Annual purchase costs for the grid company to the higher-level grid, B sjsell Annual revenue for the grid company to sell to the higher level grid, B load Annual revenue generation for grid companies in the supply area gwf The method comprises the following steps of (1) collectively collecting network fee profits from all villages for a power grid company in a distributed power generation marketization mode;
b. minimum objective function of photovoltaic power generation reduction:
wherein Qbj 2 For the reduction of photovoltaic power generation, tjs is the number of time periods, P pv,t For the unit power output value of the photovoltaic panel in the tth calculation time period, byq is a 10kV/400V public transformer set of a power grid of an area to be planned, P byq,i For the photovoltaic access capacity, P, of the ith utility transformer byqzb,i Adding photovoltaic access capacity P of special transformer to ith village collectively byq10,i Photovoltaic capacity, T of 35kV/10kV transformer connected to ith village ts,t The number of the same time periods which are represented by the tth calculation time period and run all year round, G is the actual access node set of the photovoltaic power station, and P g,i,t For the ith node, a force value, W, is derived at the t-th calculation period sjbuy Annual total power for power grid company to purchase power to higher-level power gridAmount, W sjsell Annual total electricity sold to a superior grid by a grid company;
c. network loss minimum objective function:
wherein Qbj 3 As the amount of grid network loss, W sjbuy Annual total quantity of electricity, C, to a superordinate grid for a grid company cl As a collective set of villages, W sum,i Collectively commissioning the annual total power generation of the power station for the ith village, W sjsell Annual total electricity quantity, W, sold to a superordinate grid for a grid company loadsum The total annual load of a power supply area of a power grid company is supplied;
(2) Constructing a lower-layer lean village photovoltaic installation amount investment model by taking economic benefits as a lower-layer objective function according to a distributed generation marketization constraint condition and a lean village photovoltaic installation amount investment constraint condition;
the economic gain objective function is:
Obj i ＝C pv,i +C interest,i +C yw,i +C wire,i +C gwf,i -B pv,sell,i -B pv,bt,i i∈C cl
wherein, obj i Net cost of building a photovoltaic for the ith village, C gwf,i The net charge paid to the grid company by the photovoltaic power station built for the village in year, B pv,sell,i Earnings for selling electricity in ith village under each trading mode, C gwf,i ，B pv,sell,i Determined by distributed power generation marketization constraints;
wherein, C pv,i Annual cost for photovoltaic installation, P fp,i ，P pt,i Determining the poverty-relieving photovoltaic capacity and the common distributed photovoltaic capacity for the ith village respectively, wherein r is the discount rate and T gc For engineering period, α 0 Is the residual value rate of the equipment, C pv,inv The installation cost of the unit power photovoltaic; c interest,i Loan interest for the commissioning of ordinary photovoltaics, rate is loan interest rate, C yw,i For the operation and maintenance costs of a photovoltaic power generation project, λ yw Maintenance fee for electric power, W sum,i Collectively building annual total power generation of power station for ith village, C wire,i Overhead costs for photovoltaic plant access, C w Is the unit price of the wire gf,i,k Distance, dis, for photovoltaic power plant and kth common transformer gf10,i Distance of a 35kV/10kV transformer of a photovoltaic power station, B pv,bt,i Is subsidized for the photovoltaic power generation electric quantity received all year round, lambda btfp For photovoltaic power subsidy for poverty relief, lambda btpt Is a common photovoltaic power subsidy, ratio i Poverty-relief photovoltaic proportion, Y, in photovoltaic power station built for villages byq,k For the kth transformer, a flag, Y byq10,i Connecting a 10kV voltage level zone bit for the ith village photovoltaic power station;
(3) Convex relaxation is carried out on the non-convex constraint conditions in the two models;
(4) Converting the photovoltaic installation amount investment model of the lower-layer poverty-depleted village into an upper-layer constraint condition, and realizing the solution of converting a double-layer planning model into a single-layer model;
(5) And obtaining a poverty-relief photovoltaic stationing constant volume access configuration scheme.
2. The poverty-relief photovoltaic stationing and volume-fixing method as claimed in claim 1, wherein the method for converting the lower-layer poverty-relief village photovoltaic installation volume investment model into the upper-layer constraint condition is a KKT condition conversion method.
3. The poverty-reduced photovoltaic distribution point constant volume method according to claim 1, wherein the non-convex constraint condition included in the poverty-reduced photovoltaic access model of the upper layer distribution network is a power flow equation constraint:
P ij ＝g ij V i 2 -g ij V i V j cosθ ij +b ij V i V j sinθ ij
Q ij ＝b ij V i 2 -g ij V i V j sinθ ij -b ij V i V j cosθ ij
convex approximation of the flow equation constraints:
P ij ＝g ij U i -g ij W ij +b ij T ij
Q ij ＝b ij U i -g ij W ij -b ij T ij
wherein, P ij For branch active power, Q ij Is the branch reactive power, g ij For branch conductance, b ij For branch susceptance, V i And V j Node voltages, θ, of node i and node j, respectively ij Indicates the difference of the phase angle between the two ends of the branch, U i ＝V i 2 ，W ij ＝V i V j cosθ ij ，T ij ＝V i V j sinθ ij 。
4. The poverty-reduced photovoltaic stationing and volume-fixing method according to claim 1, wherein the non-convex constraint conditions included in the lower-layer poverty-reduced village photovoltaic installation volume investment model are as follows:
ratio i ＝P fp,i /(P fp,i +P pt,i )
wherein, ratio i Poverty-relief photovoltaic proportion, P, in photovoltaic power station built for villages fp,i 、P pt,i Determining the built poverty-alleviation photovoltaic capacity and the common distributed photovoltaic capacity for the ith village respectively;
the convexity is approximated as:
or
a＝0.005Pkh i
b＝0.007Pkh i
x 3 ＝P fp,i
x 2 ＝P pt,i
x s ＝x 3 +x 2
c＝P area,i
x 1 ＝x s ratio i
wherein Pkh i Number of impoverished households for village, P fp,i ，P pt,i Poverty-alleviation photovoltaic capacity and common distributed photovoltaic capacity, P, determined to be put into operation for ith village area,i Maximum photovoltaic capacity that can be built for un-utilized land in villages.
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| CN107301470A (en) * | 2017-05-24 | 2017-10-27 | 天津大学 | A kind of power distribution network Expansion Planning stores up the dual blank-holder of addressing constant volume with light |
| CN108599235A (en) * | 2018-04-20 | 2018-09-28 | 国网湖北省电力有限公司宜昌供电公司 | A kind of constant volume method that distributed photovoltaic networks |
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| CN108599235A (en) * | 2018-04-20 | 2018-09-28 | 国网湖北省电力有限公司宜昌供电公司 | A kind of constant volume method that distributed photovoltaic networks |
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