CN114678872A - Method for analyzing consumption capability of power grid to distributed power supply - Google Patents

Method for analyzing consumption capability of power grid to distributed power supply Download PDF

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CN114678872A
CN114678872A CN202210087977.6A CN202210087977A CN114678872A CN 114678872 A CN114678872 A CN 114678872A CN 202210087977 A CN202210087977 A CN 202210087977A CN 114678872 A CN114678872 A CN 114678872A
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power
photovoltaic
distributed
line
distributed photovoltaic
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姜捷
姜建明
孙一迪
孙斐
何为民
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Jiangshan Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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Jiangshan Power Supply Co of State Grid Zhejiang Electric Power Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/40—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously

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Abstract

The invention relates to a method for analyzing the consumption capacity of a distributed power supply by a power grid, which comprises the steps of carrying out simulation calculation on the distributed photovoltaic access quantity of a 10kV power distribution network according to a load flow calculation method; analyzing influence factors of the absorption capacity of the distributed photovoltaic of the 10kV power distribution network, analyzing influences of different power supply access positions of the distributed photovoltaic on voltages of all nodes of a line, and further analyzing influence conditions of the access positions on the distributed photovoltaic access amount; further analyzing factors influencing the distributed photovoltaic absorption capacity from the aspects of different trunk lengths, different loads of lines, different lead types and sectional areas; calculating the consumption capacity of the distributed photovoltaic of the 10kV power distribution network in the typical wiring form of the power grid according to different influence factors. The invention provides a power grid distributed power supply power generation consumption analysis method based on a power grid tide and voltage analysis method, quantitatively analyzes the consumption level of a 10kV power grid to distributed power supply power generation, and provides a control standard for large-scale distributed power supply access by combining the actual condition of the power grid.

Description

Method for analyzing consumption capability of power grid to distributed power supply
Technical Field
The invention relates to the technical field of distributed power supplies, in particular to a method for analyzing the consumption capacity of a power grid to a distributed power supply.
Background
The electric energy is used as a secondary energy source, and the energy required by the production of the electric energy mainly comes from primary energy sources such as crude oil, coal, natural gas and the like. In most countries and regions of the world, thermal power generation using fossil fuels as raw materials is absolutely dominant. Primary energy sources, such as fossil fuels, petroleum and the like, are non-renewable energy sources, the existing quantity is limited, the long-term requirements of the society cannot be met, and pollution is generated in the using process, so that the influence on the earth ecological environment is great. Along with the increase of global energy crisis and the increasing of environmental awareness of people, many countries are turning to research new energy sources to seek substitution. The new energy has the characteristics of less energy, uneven distribution, low conversion efficiency and the like, and is suitable for generating power by adopting a small-capacity distributed power generation technology for new energy power generation. Distributed power generation in the form of wind power, solar power and the like is proposed in the background.
With the development of renewable energy, power electronics and other related technologies in recent years, the access of a large-scale distributed power supply to a power grid has a profound influence on the aspects of power grid planning, construction, safe and stable operation and the like of a power company. How to comprehensively consider the development of a power station and the coordinated development of the power grid absorption capacity to ensure the safe and stable operation of the power grid is important for the continuous development of one area. However, a technical scheme capable of effectively and comprehensively considering the development of the power station and the coordinated development of the power grid absorption capacity is lacking at present, and the development demand cannot be kept up to.
Disclosure of Invention
The invention solves the problems and provides a method for analyzing the consumption capacity of a power grid to a distributed power supply, wherein the method is used for analyzing the power generation consumption capacity of the power grid distributed power supply based on a power grid trend and voltage analysis method, quantitatively analyzing the consumption level of a 10kV power grid to the power generation of the distributed power supply, and providing a control standard of large-scale distributed power supply access by combining the actual condition of the power grid.
In order to realize the purpose, the following technical scheme is provided:
a method for analyzing the consumption capability of a power grid on a distributed power supply comprises the following steps:
s1, performing simulation calculation on the distributed photovoltaic access amount of the 10kV power distribution network according to a power flow calculation method, and performing modeling and electrical calculation by using the acceptance capability evaluation software of the distributed power supply of the active power distribution network and adopting an equivalent circuit form of the 10kV power distribution network;
s2, analyzing influence factors of the absorption capacity of the distributed photovoltaic of the 10kV power distribution network, analyzing influences of different power supply access positions of the distributed photovoltaic on the voltage of each node of the line, and further analyzing influence conditions of the access positions on the distributed photovoltaic access amount;
s3, further analyzing factors influencing the distributed photovoltaic absorption capacity from the aspects of different trunk lengths, different loads of circuits, different lead models and different sectional areas under the condition that the photovoltaic power supply access position is fixed;
And S4, calculating the consumption capability of the distributed photovoltaic of the 10kV distribution network in the typical wiring form of the power grid according to different influence factors, determining the maximum consumption capability range of the 10kV distributed photovoltaic, and providing a recommendation table of the distributed photovoltaic access amount of each area.
The power grid with the 10kV voltage level is complex in structure and large in scale. Due to different load levels, the characteristics of the system are different, and the distribution and the size of the power flow, the short-circuit capacity and the like are also different. The voltage deviation, harmonic wave and other indexes in the electric energy quality and the aspects of network loss, protection and the like are directly related to the operation mode and load of the system, so that a typical line needs to be analyzed and a calculation model is established for a 10kV power distribution network, and the absorption capacity analysis of the 10kV line is completed.
Preferably, the S1 specifically includes the following steps:
analyzing by load flow calculation algorithm, and determining the position of a certain region B of the lineiThe inner node i has distributed photovoltaic access, and when the distributed photovoltaic power factor is 1, the active power output by the inner node i is mainly PPV,i，UiIs the value of the node voltage, IiFor line current values, the mathematical model involved is as follows:
an objective function:
Figure BDA0003487883640000021
in the formula: p is the maximum output power of each distributed photovoltaic power supply, and M is the total number of distributed photovoltaic nodes installed in the circuit;
Node voltage constraint:
UN(1+β1)≤Ui≤UN(1+β2)
in the formula: u shapeNAt a nominal voltage of 10kV, beta1、β2Beta in a 10kV power distribution network for the voltage deviation rate specified in the technical Specification for the distributed Power supply Access to the Power distribution network1Are all-7%, beta2Are all 7 percent;
and (3) line current constraint: the distributed photovoltaic power source is connected into a power flow influencing a power distribution network, the current size and the direction can be changed, and after the distributed photovoltaic power source is connected into the distributed photovoltaic power source, the circuit current constraint is as follows:
|Ii|≤Iimax
in the formula: I.C. AiAs a line current value, IimaxIs a line safety current limit;
and finally, selecting calculation parameters and carrying out electrical calculation.
Preferably, the electrical calculation step in S1 is as follows:
s101, establishing a 10kV power distribution network and an element model thereof according to the characteristics of photovoltaic power generation and the electrical characteristics of the power distribution network;
s102, selecting typical power distribution network parameters, selecting an operation mode and selecting different access positions of the distributed photovoltaic power supply according to a typical wiring form of the power grid.
And S103, calculating the influence of different line parameters on the distributed photovoltaic access amount based on a sensitivity analysis method.
Preferably, the specific step of S103 is as follows:
selecting a certain step length access capacity, gradually increasing the distributed photovoltaic access amount, calculating the voltage quality and the load rate under various load levels, if the voltage quality and the load rate meet the requirement of safe operation, increasing the distributed photovoltaic access capacity according to a specific step length, repeating the calculation steps until the influence of the photovoltaic power generation capacity access amount on the power grid cannot meet the constraint condition, and taking the distributed photovoltaic access amount under the condition that the constraint condition is not exceeded in the last step as the maximum line access amount.
Preferably, the process of selecting the calculation parameter includes: selecting the length range of a trunk, selecting the section of a trunk lead, selecting a grid structure and selecting the power factor of a 10kV bus voltage circuit.
Preferably, the different influencing factors include: the maximum load of the 10kV power distribution network line, the maximum access amount of the photovoltaic power supply when the photovoltaic power supply is connected to the tail end of the trunk and the maximum absorption capacity of the photovoltaic power supply when the photovoltaic power supply is connected to the tail end of the branch line.
The invention has the beneficial effects that: the power generation consumption capability analysis of the power grid distributed power supply based on the power flow and voltage analysis method is used for quantitatively analyzing the consumption level of the 10kV power grid to the power generation of the distributed power supply, and the control standard of large-scale distributed power supply access is provided by combining the actual condition of the power grid.
Drawings
FIG. 1 is an equivalent circuit topology of an embodiment;
FIG. 2 is a diagram of voltage distribution of nodes after photovoltaic is connected to the front end of the trunk in the embodiment;
FIG. 3 is a diagram of voltage distribution at each node after photovoltaic is connected to the middle terminal of the trunk according to the embodiment;
FIG. 4 is a diagram of voltage distribution at each node after the end of the trunk is connected to the photovoltaic module according to the embodiment;
FIG. 5 is a graph of node voltage versus different photovoltaic access positions for an embodiment;
FIG. 6 is a graph of photovoltaic access of different wires of the embodiment at different lengths;
FIG. 7 is a graph of the photovoltaic output greater than line load condition for the example;
FIG. 8 is a graph of line load greater than photovoltaic output for an embodiment;
FIG. 9 is a graph of the photovoltaic output coefficient and the load coefficient at all four seasons for the commercial load of the embodiment;
FIG. 10 is a graph of the photovoltaic output coefficient and the load coefficient at each moment of the industrial load according to the embodiment;
FIG. 11 is a graph showing the photovoltaic output coefficient and the load coefficient at each moment of the occupancy load in the embodiment;
FIG. 12 is a graph of photovoltaic acceptance at various wire cross-sections for the examples;
FIG. 13 is a graph of the photovoltaic access amount at different trunk lengths for different load levels of the embodiment;
FIG. 14 is a graph showing the comparison of the differences between examples;
fig. 15 is a detailed flowchart of an embodiment.
Detailed Description
The embodiment is as follows:
the embodiment provides a method for analyzing consumption capability of a power grid for a distributed power supply, which specifically includes the following steps with reference to fig. 15:
s1, performing simulation calculation on the distributed photovoltaic access amount of the 10kV power distribution network according to a power flow calculation method, and performing modeling and electrical calculation by using the active power distribution network distributed power supply receptivity evaluation software in an equivalent circuit form of the 10kV power distribution network;
S2, analyzing influence factors of the absorption capacity of the distributed photovoltaic of the 10kV power distribution network, analyzing influences of different power supply access positions of the distributed photovoltaic on voltages of all nodes of a line, and further analyzing influence conditions of the access positions on distributed photovoltaic access amount;
s3, further analyzing factors influencing the distributed photovoltaic absorption capacity from the aspects of different trunk lengths, different loads of circuits, different lead types and sectional areas under the condition that the access position of the photovoltaic power supply is fixed;
and S4, calculating the consumption capability of the distributed photovoltaic of the 10kV distribution network in the typical wiring form of the power grid according to different influence factors, determining the maximum consumption capability range of the 10kV distributed photovoltaic, and providing a recommendation table of the distributed photovoltaic access amount of each area.
Mathematical computational model determination
When the maximum 10kV distributed photovoltaic access amount is calculated, analysis is carried out by a load flow calculation algorithm, and a certain area B of the line is subjected to analysisiThe inner node i has distributed photovoltaic access, and when the distributed photovoltaic power factor is 1, the active power output by the inner node i is mainly PPV,i，UiIs the value of the node voltage, IiFor line current values, the mathematical model involved is as follows:
an objective function:
Figure BDA0003487883640000051
in the formula: p is the maximum output power of each distributed photovoltaic power supply, and M is the total number of distributed photovoltaic nodes installed in the circuit.
Node voltage constraint:
UN(1+β1)≤Ui≤UN(1+β2) (2)
in the formula: u shapeNAt a nominal voltage of 10kV, beta1、β2Beta in a 10kV power distribution network for the voltage deviation rate specified in the technical Specification for the distributed power supply to the power distribution network1Are all-7%, beta2All are 7 percent.
And (3) line current constraint: the distributed photovoltaic power source is connected into a power flow influencing a power distribution network, the current size and the direction can be changed, and after the distributed photovoltaic power source is connected into the distributed photovoltaic power source, the circuit current constraint is as follows:
|Ii|≤Iimax (3)
in the formula: i isiAs a line current value, IimaxIs the line safety current limit.
Selecting calculation parameter settings:
(1) trunk length range selection
By selecting county-level line trunk line length analysis, the average trunk line length in a B power supply region is within 5km, the average trunk line length in an C, D power supply region is within 10km, the line number proportion of the trunk line length within 10km is 95.83%, and the line number proportion of the trunk line length within 10km-15km is 1.79% of the public line ratio; the ratio of the lines with the length larger than 15km to the public lines is 2.38%, so that the maximum photovoltaic acceptance is verified and calculated by selecting the range of the trunk length of the lead as 10 km.
(2) Selection of section of trunk conductor
According to the requirements of the technical guide of the power distribution network, 185mm of section of a main trunk line of a 10kV overhead line is adopted 2Above, the section of the cable trunk line conductor is preferably 300mm2The section of the line conductor is 185mm by selecting the distribution condition analysis of the county-level line section264.28% of the above, wherein 240mm260.71% of the total weight of the product. The type of the 10kV overhead insulated line is mainly JKLGYJ-10/240, the type of the overhead bare wire is mainly LGJ-240, and the type of the cable wire is mainly YJV22-8.7/15-3 x 240. Therefore, the main lead type of the calculation example is selected from three types of overhead insulation JKLGYJ-10/240, overhead bare lead LGJ-240 and cable YJV22-8.7/15-3 × 300.
(3) Selection of grid structure
The contact rate of 10kV lines is analyzed to be 95.83% by selecting a county-level line network frame. The single connection is 68, which accounts for 40.48% of the public line ratio, so the calculation grid structure of the section is mainly based on the single connection.
(4)10kV bus voltage line power factor selection
In order to avoid the situation that the voltage at the tail end of the line is too low, the voltage of a 10kV bus is set to be 10.5kV, and the power factor of the line is set to be 0.95.
An electrical calculation step:
(1) and establishing a 10kV power distribution network and an element model thereof according to the characteristics of photovoltaic power generation and the electrical characteristics of the power distribution network.
(2) And aiming at a typical wiring form of the power grid, selecting typical power distribution network parameters, selecting possible operation modes and selecting different access positions of the distributed photovoltaic power supply.
(3) And calculating the influence of different line parameters on the distributed photovoltaic access quantity based on a sensitivity analysis method. Selecting certain step length access capacity (the minimum step length is 10kW in a 10kV power grid), gradually increasing distributed photovoltaic access capacity, calculating voltage quality and load rate under various load levels, if the voltage quality and the load rate meet the requirements of safe operation, increasing the distributed photovoltaic access capacity according to the specific step length, repeating the calculation steps until the influence of the photovoltaic power generation capacity access capacity on the power grid cannot meet the constraint condition, and taking the distributed photovoltaic access capacity under the condition that the photovoltaic power generation capacity access capacity does not exceed the constraint condition as the maximum line access capacity.
Considering the influence of different access points on the distributed photovoltaic access capacity:
the section selects an equivalent circuit model for simulation, and referring to fig. 1, the configured variable capacities on the branch lines of the circuit are accumulated, and the simplified equivalent circuit model is hung on the main line by taking the single 400kVA capacity as a unit. The trunk lead section was set to overhead insulation JKLGYJ-10/240, and the trunk length was set to 10 km. The influence of different access nodes on the photovoltaic power supply access amount is mainly analyzed, so that the line load is set to be 1MW, and the equal capacity is distributed in each distribution transformer; in order to maximize the photovoltaic active output, the parameter power factor of the distributed photovoltaic power supply is set to 1. The front end (the load node closest to a transformer substation), the middle end (the load node at the position of about 1/2 of the trunk line length) and the tail end (the load node at the tail end of the trunk line length) of a trunk are used as distributed photovoltaic access positions, the voltage of each node is set as a reference when the photovoltaic capacity is not accessed, the upper limit of the voltage of each node is constrained to 10.7kV, the photovoltaic capacity accessed under the condition that the voltage of the node exceeds 10.7kV is set as the maximum photovoltaic access capacity, the 25% maximum photovoltaic access capacity is used as gradual reduction at intervals, and the influence conditions of different photovoltaic admission amounts and different access positions on the voltage of each node of the line are observed.
Under the condition of steady-state operation of a traditional power distribution network, because load consumption is connected along a line, the line loss consumption gradually reduces voltage along the tidal current direction of a feeder line. After the distributed photovoltaic is accessed to the power distribution network, the voltage of each node along the feeder line is improved due to the fact that the transmission power on the feeder line is reduced, when the distributed photovoltaic access amount reaches a certain capacity, the voltage near the access node crosses 10.7kV voltage constraint, and at the moment, the last step length access capacity is selected as the maximum distributed photovoltaic access capacity meeting the constraint condition.
Through simulation measurement and calculation, under the above parameter setting, the front end, the middle end and the tail end of the line are respectively connected to the maximum photovoltaic capacity of 3.52MW, 3.1MW and 2.51MW, and under each photovoltaic access amount level, the specific situation of the line node voltage is shown in reference to fig. 2-4:
the comprehensive results show that:
when other factors of photovoltaic access to the power distribution network are not changed, the distribution condition of the node voltage of the power distribution network is determined by the size of the photovoltaic access capacity, and the larger the access capacity is, the larger the node voltage of the power distribution network is increased.
The line node voltage gradually rises along with the increase of the photovoltaic access amount, and when the photovoltaic access capacity reaches a certain degree, the photovoltaic access point voltage is higher than the substation outlet voltage.
Under the condition that other conditions are not changed, the maximum photovoltaic access amount (2.51MW) of the tail end is taken as a photovoltaic access amount constraint condition, and when the front end, the middle end and the tail end of the line are respectively accessed and each node is observed to access distributed photovoltaic with the same capacity, the voltage change situation is specifically changed as shown in fig. 5:
under the condition of accessing the photovoltaic power supply with the same capacity, the voltage change conditions of different accessed positions are shown in table 1.
TABLE 1 case of equal capacity access to different locations versus voltage rise amplitude
Figure BDA0003487883640000081
When the photovoltaic power supply with the same capacity is connected to different positions of the circuit, the voltage of each node of the circuit is raised, and the voltage is raised to the maximum near the photovoltaic power supply access point.
The voltage lifting amplitude is 1.14% when the front end of the trunk is accessed, the voltage lifting amplitude is 2.85% when the middle end of the trunk is accessed, and the voltage lifting amplitude is 3.73% when the tail end of the trunk is accessed, so that under the same condition, the closer the distributed photovoltaic access position is to the tail end of the line, the larger the node voltage lifting amplitude is.
When the distributed photovoltaic access position is at the front end of the line, the lifting effect on the outlet voltage is large; when the terminal of the line is accessed, the voltage of the node of the whole line is greatly lifted.
Considering the influence of different trunk lengths on the distributed photovoltaic access capacity:
Under the condition that the line load condition and the lead model are not changed, a photovoltaic power supply is connected to the tail end of the trunk, the line length of the trunk is gradually changed, and the maximum photovoltaic receiving capacity change condition corresponding to different trunk lengths is observed, as shown in fig. 6:
under the condition that other conditions are not changed, only the length of the trunk line is changed, and the distributed photovoltaic access amount is reduced along with the increase of the length of the trunk line, namely the longer the line is, the less the photovoltaic access amount is.
Considering photovoltaic output risk coefficients under different load characteristics:
the load analysis method comprises the steps of selecting commercial, industrial and residential lines to carry out four-season load analysis, wherein three types of loads show the trend of two peaks and one valley from load curves of three different load characteristic lines, the commercial and residential loads are greatly influenced by four-season weather, the loads in the south are basically large in summer and autumn, the loads in the spring and winter are small, and the loads in the north are large in winter. And industrial electricity is less influenced by seasons, and the load level in four seasons is basically kept consistent.
The first peak of the business type appears at 11-12 noon, the second peak appears at 18-23 pm, mainly during business hours and relatively dense time of people flow in one day. The industrial type peaks appear during the early 9-11 pm and 14-18 pm, and the main industrial type is greatly influenced by the rest time of workers, so that the load is relatively a valley period between 12-14 pm and 18 pm to 8 pm. The first peak of the residential type appears at 11-14 noon, the second peak appears at 19-23 nights, and the residential type is mainly used in the time period of concentrated use of household appliance loads.
When the photovoltaic power supply is connected to lines with different load characteristics, the photovoltaic output capacity is also different due to different line loads, and the relationship between the line loads and the photovoltaic output can be roughly divided into two types in the time dimension: referring to fig. 7, when the line load power is greater than the photovoltaic output power, the photovoltaic output may be completely absorbed in-situ by the line; referring to fig. 8, when the photovoltaic output power is greater than the line load power, the line load can only cancel part of the photovoltaic output in situ, and the rest of the output can be transmitted to the grid through the line. However, when the photovoltaic output reaches a certain degree, the photovoltaic output can cause the power quality of the power distribution network to exceed the constraint range, and the safe operation state of the line is damaged.
In order to determine the maximum degree of accepting photovoltaic output under different load characteristics, a photovoltaic output risk coefficient concept is adopted, in a time dimension, the ratio of the line load power at a certain time in the year to the maximum load power in the year is used as a load coefficient, the ratio of the photovoltaic output power at the same time in the year to the maximum photovoltaic output power in the year is used as a photovoltaic output coefficient, and the ratio of the photovoltaic output coefficient to the load coefficient is the photovoltaic output risk coefficient.
Figure BDA0003487883640000091
Figure BDA0003487883640000092
Figure BDA0003487883640000093
In the formula: k is the photovoltaic output risk coefficient, α iIs the photovoltaic output coefficient, λiLoad factor, i is a certain time point in the year, PViTo photovoltaic output power at time i, PVmaxMaximum photovoltaic output power in the year, PLiFor loading power at point iLmaxThe annual maximum load power.
According to photovoltaic output characteristics and different line load characteristics, the four-season load coefficients with different load characteristics and the corresponding moments of the photovoltaic output coefficients are shown in the figures 9-11, and when the photovoltaic output power is higher in a certain day and the load output is lower in the same moment in the same day, the maximum photovoltaic output risk coefficient under each load characteristic can be obtained by combining the formulas (1), (2) and (3).
According to analysis, the commercial maximum photovoltaic output risk coefficient at 14 points is 3.75; the industrial maximum photovoltaic output risk coefficient when at 13 o' clock is 2.41; the resident maximum photovoltaic output risk factor when at point 13 is 2.05.
Considering the influence of different wire sections on the distributed photovoltaic access capacity:
the length of the trunk is the same (10km), the access positions are the same (the tail end of the trunk), the sectional area of a line conducting wire is taken as a variable, and overhead insulation JKLGYJ, overhead bare conductor LGJ and cable YJV are respectively selected22The cross-sectional area of the medium-voltage wire is 240mm 2、185mm2、150mm2、120mm2、95mm2、70mm2、50mm2And therefore in this range as a simulation variable. When other conditions are not changed, the sectional areas of the trunk leads of the equivalent circuit are gradually changed, and the maximum photovoltaic receiving capacity conditions corresponding to different trunk lead sectional areas are observed, referring to fig. 12.
(1) With the reduction of the sectional area of the lead, the distributed photovoltaic access amount of different types of lines is reduced. The smaller the sectional area of the lead is, the larger the line impedance is, and when the distributed photovoltaic is accessed, the larger the voltage lifting effect on the line is, namely, the accessed photovoltaic capacity is smaller.
(2) When the cross section of the wire is larger than 150mm2In time, the difference between the distributed photovoltaic receiving capacity of the cable line and the difference between the overhead bare conductor and the insulated wire is large; when the section of the wire is less than 70mm2During operation, the distributed photovoltaic receiving capacity of the overhead line insulation, the overhead bare conductor and the cable line is similar.
Calculating the maximum photovoltaic access amount of the 10kV power grid distribution type:
(1) determination of minimum load upper limit scheme of 10kV power distribution network line
Under the condition that basic parameters of a line and photovoltaic output conditions are the same, when the load of the line is larger, the distributed photovoltaic access amount of the line is larger than that of the line under the condition that the load of the line is smaller, if the distributed photovoltaic capacity which can be accepted by the line under the condition that the load of the line is larger is taken as the maximum accessible photovoltaic capacity of the line, the power quality of the line easily exceeds the upper limit of the constraint because the access amount of the distributed photovoltaic power supply is too large under the condition that the load level of the line is lower, and the use of a user side is influenced under the condition that no power control is adopted. Therefore, when analyzing the line distributed photovoltaic power generation absorption capacity, the distributed photovoltaic capacity that can be accessed when the line is under a small load should be taken as the maximum absorption capacity of the line.
The photovoltaic output time period is from 6 hours to 18 hours in the daytime, according to analysis of photovoltaic output risk coefficients of different load types, the commercial type photovoltaic output risk coefficient is the largest at 14 points, the industrial type photovoltaic output risk coefficient is the largest at 13 points, and the residential type photovoltaic output risk coefficient is the largest at 10 points, namely, the safe operation state of the line is easily damaged by photovoltaic output at the moments, so that when the photovoltaic output risk coefficient is the largest, the load coefficient at the moment is multiplied by the typical daily maximum load of the line, and the obtained load value is used as the minimum load of the line for calculating the photovoltaic access amount. The load factor in each load characteristic is shown in table 2.
TABLE 2 minimum load selection basis under different load characteristics
Load characteristic Coefficient of load Minimum load
Commerce 0.25 0.25 × maximum load
Industrial process 0.42 0.42 maximum load
Residence 0.38 0.38 × maximum load
(2) Determination of maximum load upper limit scheme of 10kV power distribution network line
In the interconnection line, single interconnection is a main wiring mode, so that the maximum power supply capacity of the single interconnection wiring mode of the 10kV line is used as the upper limit of the maximum load connected with the line to measure and calculate the maximum photovoltaic access capacity. According to the requirements of the technical guide of the power distribution network, JKLGYJ-10/240mm 2For example, the maximum transmission capacity of the overhead insulated wire in the single-connection mode of the line is 4.09MW, that is, the annual maximum load upper limit of the line is calculated to be 4.09MW, and if the line load exceeds the set maximum load upper limit, the annual maximum load of the line should be the maximum load upper limit.
(3) Maximum access calculation considering photovoltaic power supply to be connected to tail end of trunk
In the calculation example, a JKLGYJ-10/240 overhead insulated wire is taken as an example, and the trunk length range is set within 10 km. The load level takes the maximum allowable power supply capacity of the single-link line as the upper limit of the maximum load of the line, the upper limit of the maximum allowable power supply capacity of the single-link line is 4.09MW when the JKLGYJ-10/240 overhead insulated line meets the condition of 'N-1', the maximum load of the line exceeds the upper limit value, the upper limit of the minimum load is 42% of the maximum allowable power supply capacity of the single-link line, and the upper limit is divided equally by 5 equal parts downwards to represent the minimum load condition of different load levels of the line.
Referring to table 3, taking the end of the distributed photovoltaic centralized access trunk as an example, the upper limit of the voltage of each node in the feeder is constrained to 10.7kV, the power factor is set to 1, the distributed photovoltaic access amount is gradually increased, the step size of the minimum access photovoltaic capacity is 10kW, the calculation is stopped until the voltage of a certain node exceeds the constrained voltage, and the photovoltaic capacity accessed in the previous step is taken as the maximum photovoltaic access amount of the line.
TABLE 3 photovoltaic access capacity at different load levels under trunk length tolerance
Figure BDA0003487883640000121
Referring to fig. 13, it can be seen that the longer the trunk length is at different load levels, the smaller the maximum capacity of the distributed photovoltaic system can be accessed, and the smaller the load level is, the lower the maximum capacity of the distributed photovoltaic system can be accessed. According to the distributed photovoltaic access capacity trend line, under different load levels, the trend of the distributed photovoltaic maximum access capacity is similar, and the trend of the quadratic polynomial is found to be closer to the trend of the load measurement value by comparing exponential, linear, logarithmic, quadratic polynomial, power exponent and other mathematical models, so that the quadratic polynomial is adopted for access capacity trend analysis in subsequent calculation.
Under the same trunk length, distributed photovoltaic capacities accessed between different load levels have a certain value or a certain proportion difference. To determine the difference between different load levels, the correlation coefficient R is further verified when a constant value C or a proportional k is added between different load levels2Approach (c) of (d).
It can be known from the measured data by observation that, when the fixed value C is used for distinguishing, the difference between the photovoltaic access amounts of adjacent load levels is about 0.05MW within 1km, and is about 0.06MW within 1-2km, the difference between the photovoltaic access amounts of adjacent load levels in an area of 2-7km is about 0.11MW, and the difference between the photovoltaic access amounts of adjacent load levels in an area of 7-10 km is about 0.16MW within 1 km. If a proportional method is used for distinguishing according to a proportional relation k, the difference ratio of the photovoltaic access amounts of the adjacent load levels within 1km is about 1.5%, the difference ratio of the photovoltaic access amounts of the adjacent load levels within 1-2km is about 1.8%, the difference ratio of the photovoltaic access amounts of the adjacent load levels in the 2-7km area is 4%, and the difference ratio of the photovoltaic access amounts of the adjacent load levels in the 7-10 km area is about 6.3%.
Comparing the actual measured value with the actual measured value by using the actual measured value as the reference value under different load levels and comparing the value obtained by the constant method (adjacent load level plus constant value C) and the proportional method (adjacent load level is proportional to k)Calculating by regression curve method, comparing correlation coefficient R of the result of constant value method and proportional method2Values, results are shown with reference to table 4:
TABLE 4 comparison of correlation coefficients of photovoltaic access quantities in the case of fixed-value method and proportional method
Figure BDA0003487883640000131
As can be seen from fig. 14, when the photovoltaic capacity accessed at the minimum load level of 0.34MW is added with different fixed values C according to different trunk lengths, the correlation coefficient R between the obtained result and the actual measured value is obtained by using the regression curve method2Values are 0.9408(1.72MW), 0.9022(1.38MW), 0.9636(1.03MW), 0.9896(0.69MW), respectively; when the accessed photovoltaic capacity is divided into different trunk lengths and multiplied by different proportional k values on the 0.16MW minimum load level, the correlation coefficient R of the obtained result and the actual measured value20.9446(1.72MW), 0.9587(1.38MW), 0.9829(1.03MW), 0.9987(0.69MW) respectively; calculating the obtained correlation coefficient R from different load levels2In the method, the correlation coefficient obtained by the proportional method is basically larger than the correlation coefficient obtained by the fixed value method, and the correlation coefficient R is obtained by the proportional relation method 2Higher, more consistent with the actual measured values of the results, therefore, the following results can be obtained at different trunk lengths by using the proportional method to calculate the maximum acceptance of the distributed photovoltaic, referring to table 5.
TABLE 5 calculation formula of photovoltaic access under different load levels and trunk lengths
Figure BDA0003487883640000141
In the table, X represents the trunk line length, k1, k2, k3, k,4 are the proportion of the distributed photovoltaic access amount between different load levels and the minimum load level, the maximum distributed photovoltaic admission amount proportion value between adjacent loads, and NnIs in the order of different load levels, wherein N is in the range of 1,2,3,4,5, N1＝0。
(4) Maximum absorption capacity calculation considering photovoltaic power supply connected to branch line tail end
When the distributed photovoltaic is connected into the branch line, the section of the connected branch line wire is reduced, and the photovoltaic connection amount is reduced. Due to the fact that the sections of the branch wires are various in line length conditions, the photovoltaic access amount under each condition cannot be determined and researched one by one, and the equivalent line model is utilized for researching the size of the branch access distributed photovoltaic capacity. The length of the trunk is still set within 10km, and the section of the trunk lead is also selected from JKLGYJ-10/240mm2And (4) an overhead insulated wire. According to the technical specification of a power supply mode, the sectional area of a branch wire of a 10kV line is preferably 70mm 2Above, under the same conditions, the larger the line wire sectional area is, the more the photovoltaic access quantity is, and under the requirement of following the guiding rule, the distributed photovoltaic access quantity can be ensured to meet the electric energy quality constraint under all branch wire sectional areas, so that the section is 70mm2The photovoltaic capacity of the branch line and each branch line length can be used as the maximum photovoltaic access amount constraint under the condition that the photovoltaic power supply is accessed into the branch line.
Because the branch access conditions are complex and various, the minimum ratio of the photovoltaic access quantity of the corresponding branch and the trunk under the conditions of different load levels and different branch lengths is taken as the maximum photovoltaic access quantity allowed by the branch under the condition of considering the safe operation of the power grid, and the reference table 6 is referred to.
TABLE 6 ratio of photovoltaic Access of Branch to photovoltaic Access of trunk
Figure BDA0003487883640000142
(5) Line distributed photovoltaic maximum access calculation
And (3) performing input simulation on regional lines by using the distributed power supply acceptance evaluation software of the active power distribution network, and calculating the photovoltaic acceptance of each 10kV line.
The present embodiment provides a specific use case:
the method comprises the steps that input simulation is carried out on lines in a certain area by utilizing active power distribution network distributed power supply receptivity evaluation software, the number of power supply subareas is 5, the number of power supply grids is 18, 128 medium-voltage lines are totally arranged, branch terminals are mostly connected to 10kV photovoltaic access positions in a certain city, and in order to meet the safety level operation constraint of a power grid, the maximum capacity allowed to be connected to the branch terminals is used as the photovoltaic absorption capacity of the lines when the specific distributed photovoltaic access amount of each power supply grid line is measured. Through calculation, the accessible distributed photovoltaic capacity 190.03MW, the accessed amount 27.11MW and the remaining accessible amount 162.92MW of a medium-voltage power grid in a certain city can be obtained. The urban power supply area can be accessed with distributed photovoltaic capacity of 76.18MW, the proportion is 46.76%, and the rural power supply area is accessed with distributed photovoltaic capacity of 86.74MW, and the proportion is 53.24%.

Claims (6)

1. A method for analyzing the consumption capability of a power grid to a distributed power supply is characterized by comprising the following steps:
s1, performing simulation calculation on the distributed photovoltaic access amount of the 10kV power distribution network according to a power flow calculation method, and performing modeling and electrical calculation by using the active power distribution network distributed power supply receptivity evaluation software in an equivalent circuit form of the 10kV power distribution network;
s2, analyzing influence factors of the absorption capacity of the distributed photovoltaic of the 10kV power distribution network, analyzing influences of different power supply access positions of the distributed photovoltaic on voltages of all nodes of a line, and further analyzing influence conditions of the access positions on distributed photovoltaic access amount;
s3, further analyzing factors influencing the distributed photovoltaic absorption capacity from the aspects of different trunk lengths, different loads of circuits, different lead types and sectional areas under the condition that the access position of the photovoltaic power supply is fixed;
and S4, calculating the consumption capability of the distributed photovoltaic of the 10kV distribution network in the typical wiring form of the power grid according to different influence factors, determining the maximum consumption capability range of the 10kV distributed photovoltaic, and providing a recommendation table of the distributed photovoltaic access amount of each area.
2. The method according to claim 1, wherein the step S1 specifically includes the following steps:
Analyzing by load flow calculation algorithm, and determining a certain region B of the lineiThe inner node i has distributed photovoltaic access, and when the distributed photovoltaic power factor is 1, the active power output by the inner node i is mainly PPV,i，UiIs the value of the node voltage, IiFor line current values, the mathematical model involved is as follows:
an objective function:
Figure FDA0003487883630000011
in the formula: p is the maximum output power of each distributed photovoltaic power supply, and M is the total number of distributed photovoltaic nodes installed in the circuit;
node voltage constraint:
UN(1+β1)≤Ui≤UN(1+β2)
in the formula: u shapeNAt a nominal voltage of 10kV, beta1、β2Beta in a 10kV power distribution network for the voltage deviation rate specified in the technical Specification for the distributed power supply to the power distribution network1Are all-7%, beta2Are all 7 percent;
and (3) line current constraint: the distributed photovoltaic power source is connected into a power flow influencing a power distribution network, the current size and the direction can be changed, and after the distributed photovoltaic power source is connected into the distributed photovoltaic power source, the circuit current constraint is as follows:
|Ii|≤Iimax
in the formula: i isiAs a line current value, IimaxIs a line safety current limit;
and finally, selecting calculation parameters and carrying out electrical calculation.
3. The method for analyzing the consumption capability of the distributed power source by the power grid according to claim 2, wherein the step of calculating the electric power in S1 is as follows:
s101, establishing a 10kV power distribution network and an element model thereof according to the characteristics of photovoltaic power generation and the electrical characteristics of the power distribution network;
S102, selecting typical power distribution network parameters, selecting an operation mode and selecting different access positions of the distributed photovoltaic power supply according to a typical power grid connection mode.
And S103, calculating the influence of different line parameters on the distributed photovoltaic access amount based on a sensitivity analysis method.
4. The method for analyzing the consumption capability of the power grid for the distributed power supply according to claim 3, wherein the step S103 is as follows:
selecting a certain step length access capacity, gradually increasing the distributed photovoltaic access amount, calculating the voltage quality and the load rate under various load levels, if the voltage quality and the load rate meet the requirement of safe operation, increasing the distributed photovoltaic access capacity according to a specific step length, repeating the calculation steps until the influence of the photovoltaic power generation capacity access amount on the power grid cannot meet the constraint condition, and taking the distributed photovoltaic access amount under the condition that the constraint condition is not exceeded in the last step as the maximum line access amount.
5. The method for analyzing the consumption capability of the distributed power source by the power grid according to claim 2, wherein the step of selecting the calculation parameters comprises the following steps: selecting the length range of a trunk, selecting the section of a trunk lead, selecting a grid structure and selecting the power factor of a 10kV bus voltage circuit.
6. The method according to claim 1, wherein the different influencing factors comprise: the maximum load of the 10kV power distribution network line, the maximum access amount of the photovoltaic power supply when the photovoltaic power supply is connected to the tail end of the trunk and the maximum absorption capacity of the photovoltaic power supply when the photovoltaic power supply is connected to the tail end of the branch line.
CN202210087977.6A 2022-01-25 2022-01-25 Method for analyzing consumption capability of power grid to distributed power supply Pending CN114678872A (en)

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