CN113610359A - Photovoltaic access power distribution network adaptability evaluation method based on quantitative hierarchical index system - Google Patents
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Abstract
The invention relates to a photovoltaic access power distribution network adaptability evaluation method based on a quantitative hierarchical index system, which comprises the following steps: the method comprises the following steps of firstly, collecting background information and historical data of various photovoltaic power distribution networks accessed and related to a target network frame of the power distribution network to be evaluated for analysis; extracting key indexes of reliability, load rate, short-circuit current and power quality, and constructing an adaptability evaluation system; thirdly, performing adaptive evaluation on the network distribution system of the planning region to be evaluated by adopting an index scoring and weighting method; step four, layering and partitioning; fifthly, evaluating a regional power grid; calculating the adaptability score value of the regional power grid, and obtaining the adaptability evaluation result of the regional power grid according to the adaptability score; and seventhly, judging whether the photovoltaic access adaptability is provided, and taking corresponding measures. The method provides an effective tool for assisting planning personnel to reasonably consider the installation scale of regional photovoltaic and the development and planning of a matched power grid.
Description
Technical Field
The invention relates to the field of adaptability evaluation of a photovoltaic power project access area power grid, in particular to a photovoltaic access power distribution network adaptability evaluation method based on a quantitative hierarchical index system.
Background
With the continuous development of social economy, the development and utilization of energy are deepened, and the traditional energy consumption structure mainly based on fossil energy effectively supports the energy supply at the present stage, but inevitably brings about the problems of resource shortage and environmental pollution. In recent years, the development and utilization of renewable energy sources such as solar energy and the like are accelerated, and the demand of future energy development is greatly met. With the implementation of the energy development concepts of clean substitution and electric energy substitution, photovoltaic power generation has been provided with a considerable construction scale in distribution networks as an important implementation manner for promoting the development of renewable energy. Meanwhile, the photovoltaic power generation has the characteristic of high uncertainty in space-time distribution, so that the photovoltaic power generation has wide and profound influence on a power distribution network. On one hand, as the photovoltaic technology is mature day by day, the photovoltaic power generation cost is reduced year by year and policy support is provided, and the photovoltaic power generation shows more and more excellent social and economic benefits; on the other hand, the problems of source load boundary fuzzification, uncertainty aggravation and high absorption capacity presented by a power distribution system after large-scale photovoltaic access urgently need to be improved, so that power distribution network photovoltaic access adaptability analysis considering multiple evaluation elements becomes a practical requirement.
Certain planning occasions need to implement a photovoltaic installation quota policy, and the photovoltaic installation scale, density and permeability of a region need to reach specific target levels. Under this premise, the power enterprise must consider how to consume this portion of the photovoltaic quota. When the photovoltaic quota (the sum of newly-added photovoltaic installed capacity) is known, reasonably and effectively allocating the quota is a problem to be solved by the electric power enterprise function. In general, the electric energy of the conventional unit is distributed according to the generating capacity of the unit. The photovoltaic power supply is different from the traditional energy, and on the occasion that the photovoltaic power supply outputs enough power, if the consumption capacity of the power grid is insufficient, the photovoltaic power supply cannot bring the photovoltaic power output into the power balance. Therefore, besides the internal conditions of the photovoltaic system, the quota allocation mechanism should also account for the influence of grid-side factors, which includes at least two aspects: on the one hand, the power grid factor and on the other hand, the social factor.
By extracting the quantitative indexes, the operation condition of the power grid is quantitatively analyzed, and a quantitative basis and a scientific judging method are provided for the adaptability evaluation of the photovoltaic power supply connected to the power grid, so that a reasonable quantitative basis can be provided for the development and planning of regional renewable energy sources, the defects caused by certain subjectivity can be effectively overcome, and the method becomes an effective tool for assisting planning personnel to reasonably consider the installation scale of regional photovoltaic and the development and planning of a matched power grid.
Disclosure of Invention
The method has the advantages that the absorption capacity of the photovoltaic needs to be checked and checked, the technical evaluation needs to be carried out on the accessed photovoltaic from multiple aspects, the evaluation flow is applied to the evaluation of the current state and the planning state of the photovoltaic accessed power distribution network, and a beneficial conclusion for further improving the planning level of the power distribution network can be obtained. The invention provides a grading index system for evaluating the consumption level of a power distribution network, quantifies the influence of photovoltaic power sources on the grid structure, safety, reliability, electric energy quality and other aspects of the power distribution network after the photovoltaic power sources are connected, calculates comprehensive indexes to evaluate the adaptability of the system to photovoltaic admission, and provides an operable, referable and theoretical-basis photovoltaic connection adaptability evaluation process.
In order to achieve the purpose, the invention discloses a photovoltaic access power distribution network adaptability assessment method and a photovoltaic access power distribution network adaptability assessment process based on a quantitative grading index system. The overall evaluation flow is shown as the attached figure 1, and the specific steps are as follows:
the method comprises the steps of firstly, collecting background information and historical data of various photovoltaic power distribution networks accessed and related to a target network frame of the power distribution network to be evaluated for analysis.
The background data and the historical data of the photovoltaic power distribution network comprise: the method comprises the following steps of evaluating the range related to a power distribution network frame to be evaluated, the distribution range of a photovoltaic power supply, the installed capacity and the access voltage grade, and performing transformer data statistics, transformer historical operation load rate, line data statistics, line historical operation load rate, short-circuit current level, voltage deviation condition, harmonic distortion condition, voltage fluctuation, voltage unbalance condition and the like of the access power distribution network. The data collection and investigation work before evaluation needs to be deeply carried out, and relevant statistical information and data information need to be collected and provided for evaluation and analysis.
And step two, fully considering power grid planning and operation requirements, extracting key indexes in the aspects of reliability, load rate, short-circuit current, power quality and the like, and constructing an adaptability evaluation system. And the adaptability of the photovoltaic power supply to be connected into the power grid is scientifically judged through quantitative calculation of various indexes. In order to fully reflect the change condition of the running state of the power distribution network before and after power supply access, an adaptive evaluation index system is refined into 10 specific evaluation indexes, and then index weight and a scoring standard are determined according to the influence of each index on the running state of the power distribution network, wherein the specific evaluation indexes and the specific evaluation standards are shown in the following table 1.
TABLE 1 adaptability evaluation index and evaluation criteria
Wherein, x in the scoring formula is each index value, and y is the score of each index.
And thirdly, performing adaptive evaluation on the network distribution system of the planning region to be evaluated by adopting an index scoring and weighting method. And collecting or counting operation data and data of the area to be evaluated after the photovoltaic power supply is accessed, and calculating to obtain each index value and corresponding index score in the adaptive index evaluation table. Extracting typical boundaries and calculation scenes depending on calculation according to basic data of the power grid, and fitting the output characteristics and probability distribution of photovoltaic units and the like; determining a probability distribution model (usually a normal distribution model) of the load by combining the load prediction result; generating a certain number of output combination and analysis scenes which obey probability distribution; and calculating the load flow distribution under the determined scene and source load combination, and calculating the line load rate by using the load flow calculation result of each branch and the allowable transmission capacity upper limit. The flow of the random power flow evaluation is shown in fig. 2.
And calculating to obtain the weighted score value of each index and obtain an adaptability analysis result by combining the following formula:
in the formula: m is the total score of the regional power grid adaptability under the evaluated scene; y iskThe k-th specific index value of the regional power grid under the evaluated scene; m is the index item number of the regional power grid under the evaluated scene, and m is less than or equal to 10; w is akThe k-th specific index weight of the selected regional power grid, and the sum of the m weights is 1.
And step four, if the selected regional power grid to be evaluated is large and integral analysis is inconvenient, a layering and partitioning idea is adopted, and the power grid evaluation range is divided into three layers of regional power grids, power grids of all voltage levels and power grids of all partitions for evaluation. If a subarea power grid with weak electrical connection or relatively independent subarea power grids exist in the same voltage class and each subarea has power supply access, the subarea power grid is further divided. The grid hierarchy is shown in figure 3.
And fifthly, after the layering and the partitioning are finished, evaluating the regional power grid. The adaptability score of each subarea power grid is calculated firstly, and then the adaptability score of each voltage grade power grid is calculated according to the following formula.
In the formula: miGrading the adaptability of the voltage grade power grid with the sequence number i; wi jThe voltage class is numbered i, and the partition is numbered AjAdaptive scoring weight of the partitioned grid of (A)jThe sum of the term weights should equal 1.
Calculating the adaptability score value of the regional power grid, and obtaining the adaptability evaluation result of the regional power grid according to the adaptability score:
in the formula: mAREAGrading the adaptability of the regional power grid after the photovoltaic power supply is connected; n is the number of different voltage grades evaluated by the regional power grid, and n is less than or equal to 5; wiThe adaptive index weight of the voltage grade power grid with the voltage grade serial number i is obtained, and the sum of n terms of weight is equal to 1.
Step seven: aiming at an evaluation object and a power distribution network frame with the adaptability evaluation score value smaller than 0, considering that the evaluation object and the power distribution network frame do not have photovoltaic access adaptability, a targeted improvement measure needs to be taken, and after the measure is taken, the adaptability evaluation can be carried out again to calculate the score value; and regarding the evaluation object and the power distribution network frame with the adaptability evaluation score value larger than 0, the photovoltaic access adaptability is considered to be possessed.
The invention has the beneficial effects that:
the method disclosed by the invention starts from four key dimensions of power grid reliability, load rate, short-circuit current and power quality, and carries out quantitative analysis on the operation condition of the power grid by extracting quantitative indexes, and provides quantitative basis and scientific judgment method for the photovoltaic power supply connected to the power grid.
Aiming at the problem that quantitative basis is lacked in quantitative evaluation of the digestion capacity caused by large development scale of the photovoltaic power supply, the invention provides a power distribution network adaptability evaluation flow based on quantitative grading indexes, and the power distribution network adaptability evaluation flow is applied to evaluation of the current state and the planning state of a photovoltaic access power distribution network, so that a beneficial conclusion that the power distribution network planning level can be improved in a targeted manner is obtained. Firstly, a hierarchical index system for evaluating the consumption level of the power distribution network is introduced, the influence of the photovoltaic power supply on the grid structure, safety, reliability, power quality and the like of the power distribution network after the photovoltaic power supply is connected is quantified through indexes, and then comprehensive indexes are calculated to evaluate the adaptability of the system to photovoltaic acceptance, so that an operable flow and basis are provided for guiding the planning and design of the system, excavating weak links of the grid and improving the investment proficiency level of the system.
The method can provide a scientific, efficient, reasonable and orderly planning process for the power distribution network with large-scale and large-capacity photovoltaic power access and a scene to be evaluated, promotes the power distribution network frame with increasingly large scale and increasingly complex elements to realize safe, reliable, economic and reasonable transition to a target network frame, and plays a beneficial leading role in continuously improving the lean level of power distribution network planning in China.
The conception, the specific structure and the technical effects of the present invention will be further described with reference to the accompanying drawings to fully understand the objects, the features and the effects of the present invention.
Drawings
FIG. 1 shows a flow chart of an implementation of the present invention.
Fig. 2 shows a line load rate calculation random power flow operation flow of the present invention.
Fig. 3 shows a schematic diagram of a layered partitioning structure of a power distribution network according to the present invention.
Fig. 4 shows a rack topology diagram of an embodiment of the invention.
Fig. 5-1 shows a schematic diagram of bus voltage levels after photovoltaic access to a platform a area according to an embodiment of the present invention.
Fig. 5-2 shows a schematic diagram of bus voltage levels after photovoltaic access to a station B area according to an embodiment of the present invention.
Fig. 5-3 show schematic diagrams of bus voltage levels after photovoltaic access to a cell C zone according to embodiments of the invention.
Fig. 5-4 show schematic diagrams of bus voltage levels after photovoltaic access to a D-stage area according to embodiments of the invention.
Fig. 6 shows a schematic diagram of the net rack reconstruction and lifting according to the embodiment of the invention.
Fig. 7-1 is a schematic diagram of bus voltage levels after photovoltaic access to a platform a area after grid transformation and lifting are completed according to an embodiment of the invention.
Fig. 7-2 is a schematic diagram showing bus voltage levels after photovoltaic access to a zone B area after grid transformation and lifting are completed according to the embodiment of the invention.
Fig. 7-3 are schematic diagrams illustrating bus voltage levels after photovoltaic access to a district C after grid transformation and lifting are completed according to an embodiment of the invention.
Fig. 7-4 are schematic diagrams illustrating bus voltage levels after photovoltaic access to a D-stage area after grid transformation and lifting are completed according to an embodiment of the invention.
Detailed Description
Example 1: scene assessment with photovoltaic access adaptability
The method comprises the steps of selecting a photovoltaic poverty alleviation grid-connected project in a certain area as an analysis object, researching the adaptability assessment evaluation and analysis of the power distribution network under the photovoltaic access scene in the area, and applying the method disclosed by the invention by adopting the flow shown in the attached drawing 1 as a specific implementation mode example.
Step one to step two: determining the evaluation area range of the power grid, and collecting the basic data of the power grid of the selected area, wherein the basic data comprises power supply data, transformer data, line data, load data and the like.
The power grid of the area to be evaluated is powered by 10kV lines of a peripheral 35 kV A station, and comprises 4 transformer areas which are respectively a transformer area A to a transformer area D, and each transformer area supplies power to users through distribution transformation. The installed photovoltaic power generation capacity of each household is 3kWp, the total number of the household is 100, and the total installed capacity is 300 kWp. Each household is directly connected to a user distribution box through 220V for grid connection, as shown in fig. 4, a network topology structure of a distribution network in a planning scene is shown, and the following table 2 shows the number and capacity of photovoltaic power generation installation users in 4 distribution areas.
TABLE 2 photovoltaic installation Capacity
The scene load is mainly lighting equipment, the daily load is small, the daily maximum load is about 80kW, and the daily minimum load is about 10 kW.
Step three: and calculating each index value in the evaluation index system according to the basic data of the power grid. After the 300kWp photovoltaic power generation in the region is connected into a system, the bus voltage of each region is within the range required by the national standard. The following table 3 shows the voltage unbalance of the 10kV buses of the 4 transformer substations, and the voltage unbalance of the 10kV buses of the 4 transformer substations does not exceed the specified range according to the specification of GB/T-15543-.
TABLE 3 three-phase voltage unbalance
| Platform area | Degree of unbalance (%) |
| Platform area A10 kilovolt bus | 0.009 |
| Platform zone B10 kilovolt bus | 0.009 |
| Platform C10 KV bus | 0.01 |
| Platform area D10 kilovolt bus | 0.01 |
The distribution network safety analysis results calculated by using a random power flow method after photovoltaic power generation is accessed are shown in the following table 4:
TABLE 4 statistical table of security results
Step four: and obtaining an adaptability evaluation and analysis conclusion according to the index adaptability calculation result of the photovoltaic access power distribution network. And (3) substituting the index calculation result into a calculation formula of the formula (1), wherein the photovoltaic access comprehensive score of the power distribution network to be evaluated is 0.5, and the score conclusion is that the power distribution network has photovoltaic access adaptability.
Example 2: scene assessment without photovoltaic access adaptability and after transformation
The method comprises the steps of selecting a photovoltaic poverty alleviation grid-connected project in a certain area as an analysis object, researching the adaptability assessment evaluation and analysis of the power distribution network under the photovoltaic access scene in the area, and applying the method disclosed by the invention by adopting the flow shown in the attached drawing 1 as a specific implementation mode example.
Step one to step two: determining the evaluation area range of the power grid, and collecting the basic data of the power grid of the selected area, wherein the basic data comprises power supply data, transformer data, line data, load data and the like. The basic data of the selected area are the same as in example 1.
Step three: and calculating each index value in the evaluation index system according to the basic data of the power grid. After the 300kWp photovoltaic power generation in the area is connected into a system, the bus voltages of the transformer area B and the transformer area C are within the range required by the national standard, the bus voltage lifting amplitude of the transformer area A and the transformer area D is large, the maximum values are 1.15pu and 1.1pu respectively, the voltage is out of limit, and the requirement of the national standard is not met. The attached figures 5-1 to 5-4 are voltage curves of different transformer areas after photovoltaic power generation is connected. The distribution network safety analysis results calculated by using a random power flow method after the 10kV bus voltage unbalance of the 4 transformer areas and the photovoltaic power generation are accessed are the same as those in embodiment 1, as shown in table 3 and table 4.
Step four: and obtaining an adaptability evaluation and analysis conclusion according to the index adaptability calculation result of the photovoltaic access power distribution network. And (3) substituting the index calculation result into a calculation formula of the formula (1), wherein the photovoltaic access comprehensive score of the power distribution network to be evaluated is-7.5, and the score conclusion is that the power distribution network does not have adaptability.
Step five: according to the evaluation result and conclusion of the selected evaluation power distribution network area, targeted improvement and promotion should be carried out on the power distribution network frame. The reconstruction measures involved in the planning scheme are as follows: the power utilization condition (for example, A phase) of partial users in 4 distribution areas is changed (changed into C phase), and the balance of the number of A, B, C three-phase users is ensured. And transforming part of circuits of the transformer area A and the transformer area D from the current small-section power transmission line and replacing the partial circuits with large-section power transmission lines, so as to strengthen the power grid frame for the trunk. And part of photovoltaic power generation and load of the transformer area B and the transformer area C are changed into lines, so that the transformer area access capacity is balanced as much as possible, and the terminal photovoltaic access distance is shortened. Fig. 6 is a structure diagram of the transformed grid structure, and the following table 5 shows photovoltaic installation capacity of 4 transformer areas in the region after transformation.
TABLE 5 photovoltaic installation Capacity after reforming
By modifying the electricity phase sequence for part of users (for example, changing A phase into B phase), and enhancing the adjustment of the number of users between a station main line and 4 stations, after the 300kWp photovoltaic power generation 220V of the area is connected into a system, the bus voltages of the 4 stations are within the range required by the national standard and do not exceed the standard. Fig. 7 is a voltage curve for the modified back land a and land D.
After the transformation scheme is implemented, indexes such as short-circuit current, voltage deviation, harmonic distortion, harmonic current, voltage fluctuation and the like meet requirements. After the transformation, the average load rate of the line in each district is reduced to 62% from 88% before the access, and the rating value of the full (over) load rate of the line is 2.5 points. The comprehensive evaluation result is 2.5 points, the evaluation result is more than 0 point, and the method belongs to the field of 'strong adaptability'.
The embodiment represents a household photovoltaic power station, the load of the power supply access area is generally small, and the problems that the transmission capacity of distribution and transformation is limited, the current carrying capacity of a low-voltage line cannot meet the requirement and the voltage is higher are mainly caused. The necessity of adapting to photovoltaic large-scale development and access targeted improvement and promotion of a rural power grid weak grid structure is fully explained by combining the quantitative grading index and the adaptability evaluation method provided by the invention.
Claims (10)
1. A photovoltaic access distribution network adaptability assessment method based on a quantitative hierarchical index system is characterized by comprising the following steps:
the method comprises the following steps of firstly, collecting background information and historical data of various photovoltaic power distribution networks accessed and related to a target network frame of the power distribution network to be evaluated for analysis; step two, considering power grid planning and operation requirements, extracting key indexes of reliability, load rate, short-circuit current and power quality, and constructing an adaptability evaluation system; thirdly, performing adaptive evaluation on the network distribution system of the planning region to be evaluated by adopting an index scoring and weighting method; step four, layering and partitioning; step five, after layering and partitioning are completed, evaluating a regional power grid; calculating the adaptability score value of the regional power grid, and obtaining the adaptability evaluation result of the regional power grid according to the adaptability score; and seventhly, judging whether the photovoltaic access adaptability is provided, and taking corresponding measures.
2. The photovoltaic access power distribution network adaptability evaluation method based on the quantitative hierarchical index system according to claim 1, wherein in the step one, the background data and the historical data of various photovoltaic power distribution networks comprise the range related to the power distribution network frame to be evaluated, the distribution range, the installed capacity and the access voltage grade of the photovoltaic power supply, and the statistics of transformer data, the historical operating load rate of the transformer, the statistics of line data, the historical operating load rate of the line, the short-circuit current level, the voltage deviation condition, the harmonic distortion condition, the voltage fluctuation and the voltage unbalance condition of the access power distribution network.
3. The photovoltaic access power distribution network adaptability evaluation method based on the quantitative hierarchical index system as claimed in claim 1, wherein in the second step, the adaptability of the photovoltaic power supply to the power distribution network is scientifically judged through quantitative calculation of various indexes, in order to fully reflect the change situation of the power distribution network operation state before and after power supply access, the adaptability evaluation index system is refined into 10 specific evaluation indexes, and then index weight and scoring standards are determined according to the influence of each index on the power distribution network operation state.
4. The photovoltaic access power distribution network adaptability evaluation method based on the quantitative hierarchical index system according to claim 1, characterized in that operation data and data after photovoltaic power access of an area to be evaluated are collected or counted in the third step, and index values and corresponding index scores in an adaptability index evaluation table are calculated; extracting typical boundaries and calculation scenes depending on calculation according to the basic data of the power grid, and fitting the output characteristics and probability distribution of the photovoltaic units; determining a probability distribution model of the load by combining the load prediction result; generating an output combination and an analysis scene which obey probability distribution; and calculating the load flow distribution under the determined scene and source load combination, and calculating the line load rate by using the load flow calculation result of each branch and the allowable transmission capacity upper limit.
5. The photovoltaic access distribution network adaptability evaluation method based on the quantitative hierarchical index system according to claim 4, wherein the probability distribution model is a normal distribution model.
6. The photovoltaic access distribution network adaptability assessment method based on the quantitative hierarchical index system according to claim 5, characterized in that the weighted score values of the indexes are calculated and the adaptability analysis result is obtained by combining the formula (1):
in the formula: m is a scoreEstimating the total score of regional power grid adaptability under the scene; y iskThe k-th specific index value of the regional power grid under the evaluated scene; m is the index item number of the regional power grid under the evaluated scene, and m is less than or equal to 10; w is akThe k-th specific index weight of the selected regional power grid, and the sum of the m weights is 1.
7. The photovoltaic access power distribution network adaptability evaluation method based on the quantitative hierarchical index system according to claim 1, characterized in that in the fourth step, if the selected regional power grid to be evaluated is large and not convenient for overall analysis, a hierarchical zoning idea is adopted to divide the power grid evaluation range into three layers of the regional power grid, each voltage level power grid and each subarea power grid for evaluation, and if a subarea power grid with weak electrical connection or relatively independent electrical connection exists in the same voltage level and each subarea has power access, a subarea power grid should be further divided.
8. The photovoltaic access distribution network adaptability assessment method based on the quantitative hierarchical index system as claimed in claim 1, wherein in step five, the adaptability score of each subarea power grid is calculated first, and then the adaptability score of each voltage level power grid is calculated according to a formula (2).
In the formula: miGrading the adaptability of the voltage grade power grid with the sequence number i; wi jThe voltage class is numbered i, and the partition is numbered AjAdaptive scoring weight of the partitioned grid of (A)jThe sum of the term weights should equal 1.
9. The photovoltaic access distribution network adaptability assessment method based on the quantitative hierarchical index system according to claim 1, wherein the calculation formula of the adaptability evaluation result of the regional power grid obtained according to the adaptability score in the sixth step is as follows (3):
in the formula: mAREAGrading the adaptability of the regional power grid after the photovoltaic power supply is connected; n is the number of different voltage grades evaluated by the regional power grid, and n is less than or equal to 5; wiThe adaptive index weight of the voltage grade power grid with the voltage grade serial number i is obtained, and the sum of n terms of weight is equal to 1.
10. The photovoltaic access distribution network adaptability evaluation method based on the quantitative hierarchical index system according to claim 1, characterized in that in step seven, for evaluation objects and distribution network racks with an adaptability evaluation score value less than 0, it is considered that the evaluation objects and distribution network racks do not have photovoltaic access adaptability, a targeted improvement measure needs to be taken, and after the measure is taken, the adaptability evaluation can be performed again to calculate the score value; and regarding the evaluation object and the power distribution network frame with the adaptability evaluation score value larger than 0, the photovoltaic access adaptability is considered to be possessed.
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