A method for evaluating the new energy absorption capacity of distribution networks based on load simultaneity rate

Abstract

The present invention provides a method for evaluating the new energy absorption capacity of a distribution network based on load simultaneity, including the following steps: collecting historical data and grid information of a 10kV distribution network area; normalizing the historical data to obtain a characteristic curve of total load and new energy output; establishing a flow calculation topology grid according to the grid information; establishing a relationship model between new energy absorption capacity and new energy output; and using a binary cyclic approximation method to obtain the maximum absorption capacity of the power grid for new energy. The present invention uses a binary cyclic approximation method to obtain the maximum absorption capacity of the distribution network for new energy based on a relationship model between new energy absorption capacity and new energy output normalized by historical load data; the capacity of the distribution network to absorb new energy obtained by the present invention is higher than that obtained by the traditional method, and the improvement is more obvious, and the absorption capacity of the present invention is used to plan the construction of the grid connection of new energy, which can provide a planning reference capacity for the grid connection of new energy to a greater extent.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy consumption in power systems, and in particular to a method for evaluating the new energy consumption capacity of a distribution network based on load simultaneity rate. Background Art

[0002] With the development of social economy, environmental pollution and the depletion of fossil fuels have become the two main culprits that hinder the sustainable development of mankind. Developing clean renewable energy is one of the effective solutions to environmental problems and energy constraints, and it is also the only way for human society to achieve sustainable development. At present, new energy power generation has received much attention both at home and abroad. With the advancement of technology and the support of governments of various countries, the installed capacity of new energy power generation has ushered in rapid development in the past decade.

[0003] With the vigorous development and popularization of new energy, its application in daily life is becoming more and more extensive. The scale of new energy will also be further expanded. The higher demand for new energy grid-connected construction poses a certain impact risk to the original distribution network. Therefore, the planning and construction of new energy needs to be done with high precision, high safety and high reliability.

[0004] At present, the development stage of new energy in my country has shifted from supplementary energy to large-scale substitution. A large number of distributed wind and light new energy have poured into the distribution network, making the operation of the distribution network more uncertain and causing serious random power disturbances. At the same time, while new energy has brought significant benefits to the whole society, its own absorption problem has become increasingly severe, becoming one of the main factors restricting the development and utilization of new energy in the future. In the initial stage of the research on the evaluation of new energy absorption capacity, the evaluation of new energy absorption capacity mainly serves the planning of the power system and is used to determine the maximum installed capacity of new energy. The evaluation using the constraint factor method is relatively simple, but because only the influence of a certain constraint factor is considered, the results obtained by this evaluation method are not general, and can only reflect the overall absorption capacity of the system, and cannot quantify the absorption capacity of the regional power grid and nodes, and cannot fully reflect the absorption capacity of new energy.

[0005] In the existing research on the assessment of new energy acceptance, the solution is generally roughly calculated according to the capacity redundancy method, which lacks consideration of the compatibility of the system operation sequence with the access of new energy. The resulting absorption capacity cannot fully tap the distribution network's carrying capacity for the access of new energy, and cannot fully tap the distribution network's grid connection limit and utilization benefits for the grid connection of new energy. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a method for evaluating the new energy consumption capacity of a distribution network based on load simultaneity rate.

[0007] The technical solution of the present invention is: a method for evaluating the new energy consumption capacity of a distribution network based on load simultaneity rate, comprising the following steps:

[0008] S1) Collect historical data and grid information of 10kV distribution network area, with the collection time interval of 15 minutes;

[0009] S2), normalizing the historical data collected in step S1) to obtain a characteristic curve of total load and new energy output;

[0010] S3), establishing a power flow calculation topology grid according to the grid information collected in step S1);

[0011] S4) Establish a relationship model between new energy consumption capacity and new energy output;

[0012] S5) Use the binary cycle approximation method to obtain the maximum absorption capacity of the power grid for new energy.

[0013] Preferably, in step S1), the historical data collected includes regional total load data and new energy output data for the past year.

[0014] Preferably, in step S1), the collected grid information includes the regional distribution network topology, line impedance and the length of each trunk branch.

[0015] Preferably, in step S2), the normalization process of the historical load data is specifically as follows:

[0016] S201), firstly, according to the load data of the past year, the characteristic curve of the regional overall load and the output of new energy is calculated, and the relevant calculation is as follows:

[0017]

[0018]

[0019] Where P z (t) and P xny (t) are the total load characteristics and new energy output characteristics of the region at time t; P z,i (t) and P xny,i (t) are the total load and renewable energy output at time t on day i in the past year;

[0020] S202), then normalize the total load characteristics and the new energy output characteristics. Since the data collection time interval is 15 minutes, there are 96 data points collected in one day, so the normalization is as follows:

[0021]

[0022] Where P * (t) is the load / output normalized value at time t; P(t) is the load value / output at time t; P max and P min They are the maximum load / output and minimum load / output in a day respectively.

[0023] Preferably, in step S4), a relationship model between the new energy consumption capacity and the new energy output is established, which is as follows:

[0024] S401), the absorption capacity refers to the capacity of the distribution network that allows the construction of new energy equipment, the unit is kW, and the regional absorption capacity is P xiao , the new energy output allowed to be carried at time t is P xiao (t), then P xiao and P xiao (t) satisfies the following relationship:

[0025] P xiao =min[P xiao (1),P xiao (2),...,P xiao (95),P xiao (96)];

[0026]

[0027] Where P xiao is the minimum value of renewable energy output that can be absorbed at each time of the day; P xny (t) is the output amplitude of new energy; Normalize the output value of new energy.

[0028] Preferably, in step S5), the maximum absorption capacity of the distribution network for new energy is obtained by using a binary cycle approximation method, as follows:

[0029] S501), initialize three absorption capacities, including large, medium and small values ​​P xiao，1 , P xiao,2 and P xiao，3 ,in,

[0030] P jie，1 =0,

[0031] P jie，3 , should be achieved greatly,

[0032] P jie,2 =(P jie,1 +P jie,3 ) / 2;

[0033] The original total load of each node of the grid is calculated as follows:

[0034]

[0035] Where P k (t) is the original total load of the kth node at time t; P z (t) is the total load of the distribution network; K is the number of load nodes;

[0036] S502), the absorption capacity is the capacity of a node that allows the addition of new energy sources. The output amplitudes brought by the addition of new energy sources are calculated according to the three absorption capacities. The output amplitudes corresponding to the small, medium and large absorption capacities are:

[0037]

[0038]

[0039]

[0040] Assume that the node where the new energy source is connected is node m, then the load input for the power flow calculation of node m is:

[0041] P m (t)-P xny (t);

[0042] in, is the normalized value of new energy output, P m (t) is the original total load of node m at time t;

[0043] S503), under the three absorption capacities, calculate the power flow at each moment in a day, and obtain the maximum feeder current I under the three absorption capacities in a day 1,max ,I 2,max ,I 3,max , and the maximum voltage per unit value U of all nodes in a day 1,max ,U 2,max ,U 3,max ;

[0044] S504) Make an over-limit judgment. Under a certain absorption capacity, if the power flow result satisfies that the maximum current exceeds the feeder current carrying capacity, or the maximum node voltage is greater than the upper limit of the voltage, it means that the absorption capacity will cause unsafe operation of the distribution network and should be reduced. The relevant over-limit formulas for current and voltage are as follows:

[0045] I max >I lim ;

[0046] U max >1.07U N ;

[0047] In the formula, Ilim U is the current carrying capacity of the feeder; N is the voltage reference value;

[0048] S505) The regional power flow results of the three absorption capacities are judged to be over-limit. If the voltage or current exceeds the limit, it is marked as 1, and if not, it is marked as 0. Thus, the over-limit situation r under the absorption capacity of small, medium and large is obtained. 1 , r 2 , r 3 ;

[0049] S506) Update the small, medium and large values ​​of the absorption capacity according to the over-limit situation and by using the dichotomy method. The updating method is as follows:

[0050] If r 1 =0,r 2 =0,r 3 =1, indicating that the small median value does not exceed the limit, and the large value exceeds the limit, then the original median absorption capacity needs to be assigned to the small value, and the large value absorption capacity remains unchanged. The median absorption capacity is the mean value after the large and small values ​​are updated, as shown in the following formula:

[0051]

[0052] S507), repeat step S2) with the updated absorption capacity until the absorption capacity accuracy is less than 10 -4 , then the final distribution network area absorption capacity P is output xiao,2 , the absorption capacity accuracy ε is calculated as follows:

[0053] ε=P xiao,2 -P xiao,1 .

[0054] The beneficial effects of the present invention are:

[0055] 1. The present invention adopts a relationship model between the new energy absorption capacity and the new energy output based on the normalization of historical load data, and adopts a binary cycle approximation method to obtain the maximum absorption capacity of the distribution network for new energy;

[0056] 2. The capacity of the distribution network of the present invention to add new energy is higher than that of the traditional method, and the improvement is more obvious. In addition, the construction planning of the new energy grid connection can be carried out by using the absorption capacity of the present invention, which can provide planning reference capacity for the new energy grid connection to a greater extent, and meet the construction needs under the background of the vigorous promotion of new energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Figure 1 It is a flow chart of the method of the present invention;

[0058] Figure 2 A power flow grid diagram established in Example 2 of the present invention;

[0059] Figure 3 is the original load characteristic diagram of Example 2 of the present invention;

[0060] Figure 4 This is a new energy output characteristic diagram of Example 2 of the present invention; DETAILED DESCRIPTION

[0061] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings:

[0062] Example 1

[0063] like Figure 1 As shown, this embodiment provides a method for evaluating the new energy consumption capacity of a distribution network based on load concurrency rate, comprising the following steps:

[0064] S1) Collect historical data and grid information of the 10kV distribution network area, with the collection point time interval being 15 minutes; in this embodiment, the collected historical data includes the regional total load data and new energy output data for the past year. The collected grid information includes the regional distribution network topology, line impedance and the length of each trunk branch.

[0065] S2), normalize the historical data collected in step S1) to obtain the characteristic curve of total load and new energy output, as follows: S201), first calculate the characteristic curve of regional overall load and new energy output based on the load data of the past year, and the relevant calculation is as follows:

[0066]

[0067]

[0068] Where P z (t) and P xny (t) are the total load characteristics and new energy output characteristics of the region at time t; P z,i (t) and P xny,i (t) are the total load and renewable energy output at time t on day i in the past year;

[0069] S202), then normalize the total load characteristics and the new energy output characteristics. Since the data collection time interval is 15 minutes, there are 96 data points collected in one day, so the normalization is as follows:

[0070]

[0071] Where P * (t) is the load / output normalized value at time t; P(t) is the load value / output at time t; P maxand P min They are the maximum load / output and minimum load / output in a day respectively.

[0072] S3), establishing a power flow calculation topology grid according to the grid information collected in step S1);

[0073] S4) Establish a relationship model between new energy consumption capacity and new energy output, as follows:

[0074] S401), the absorption capacity refers to the capacity of the distribution network that allows the construction of new energy equipment, the unit is kW, and the regional absorption capacity is P xiao , the new energy output allowed to be carried at time t is P xiao (t), then P xiao and P xiao (t) satisfies the following relationship:

[0075] P xiao =min[P xiao (1),P xiao (2),...,P xiao (95),P xiao (96)];

[0076]

[0077] Where P xiao is the minimum value of renewable energy output that can be absorbed at each time of the day; P xny (t) is the output amplitude of new energy; Normalize the output value of new energy.

[0078] S5) Use the binary cycle approximation method to obtain the maximum absorption capacity of the power grid for new energy, as follows:

[0079] S501), initialize three absorption capacities, including large, medium and small values ​​P xiao，1 , P xiao,2 and P xiao，3 ,in:

[0080] P jie，1 =0,

[0081] P jie，3 , should be achieved greatly,

[0082] P jie,2 =(P jie,1 +P jie,3 ) / 2;

[0083] The original total load of each node of the grid is calculated as follows:

[0084]

[0085] Where P k (t) is the original total load of the kth node at time t; P z (t) is the total load of the distribution network; K is the number of load nodes;

[0086] S502), the absorption capacity is the capacity of a node that allows the addition of new energy sources. The output amplitudes brought by the addition of new energy sources are calculated according to the three absorption capacities. The output amplitudes corresponding to the small, medium and large absorption capacities are:

[0087]

[0088]

[0089]

[0090] Assume that the node where the new energy source is connected is node m, then the load input for the power flow calculation of node m is:

[0091] P m (t)-P xny (t);

[0092] in, is the normalized value of new energy output, P m (t) is the original total load of node m at time t;

[0093] S503), under the three absorption capacities, calculate the power flow at each moment in a day, and obtain the maximum feeder current I under the three absorption capacities in a day 1,max ,I 2,max ,I 3,max , and the maximum voltage per unit value U of all nodes in a day 1,max ,U 2,max ,U 3,max ;

[0094] S504) Make an over-limit judgment. Under a certain absorption capacity, if the power flow result satisfies that the maximum current exceeds the feeder current carrying capacity, or the maximum node voltage is greater than the upper limit of the voltage, it means that the absorption capacity will cause unsafe operation of the distribution network and should be reduced. The relevant over-limit formulas for current and voltage are as follows:

[0095] I max >I lim ;

[0096] U max >1.07U N ;

[0097] In the formula, I lim U is the current carrying capacity of the feeder;N is the voltage reference value;

[0098] S505) The regional power flow results of the three absorption capacities are judged to be over-limit. If the voltage or current exceeds the limit, it is marked as 1, and if not, it is marked as 0. Thus, the over-limit situation r under the absorption capacity of small, medium and large is obtained. 1 , r 2 , r 3 ;

[0099] S506) Update the small, medium and large values ​​of the absorption capacity according to the over-limit situation and by using the dichotomy method. The updating method is as follows:

[0100] If r 1 =0,r 2 =0,r 3 =1, indicating that the small median value does not exceed the limit, and the large value exceeds the limit, then the original median absorption capacity needs to be assigned to the small value, and the large value absorption capacity remains unchanged. The median absorption capacity is the mean value after the large and small values ​​are updated, as shown in the following formula:

[0101]

[0102] S507), repeat step S2) with the updated absorption capacity until the absorption capacity accuracy is less than 10 -4 , then the final distribution network area absorption capacity P is output xiao,2 , the absorption capacity accuracy ε is calculated as follows:

[0103] ε=P xiao,2 -P xiao,1 .

[0104] Example 2

[0105] This embodiment takes a 33-node overhead line grid as an example. Figure 2 The cross-sectional area of ​​the overhead line used is 240mm 2 , reactance and resistance are 0.307 and 0.13Ω / kM respectively, the total length of the feeder is 5km, the lines between each node are of equal length, the feeder current is 495A, the wiring form is 3-1 wiring, and the goal is to consider connecting new energy from node 16. The original load characteristics are as follows Figure 3 As shown in Figure 2, the output characteristics of new energy are as follows: Figure 4 The original load sets the original load maximum load rate gradient, including 0%, 20%, 40%, and 60%, and the original load is evenly distributed to each node.

[0106] The simulation results and analysis are shown in Table 1:

[0107] Table 1 Comparison of evaluation of new energy consumption capacity

[0108]

[0109] It can be seen from Table 1 that when the maximum load rate of the original load is 0%, there is no peak-shifting of the original load and the output of new energy. Therefore, the absorption capacity obtained by the two methods is the redundant capacity of the distribution network. When the load rate is 20%, 40%, and 60%, the capacity of the distribution network to add new energy output obtained by the present invention is higher than that of the traditional method, and the improvement is more obvious. This embodiment takes a 33-node overhead line grid as an example, and verifies through simulation that the capacity of the distribution network to add new energy obtained by the present invention is higher than that of the traditional method, and the improvement is more obvious. If the construction plan of the new energy grid connection is carried out according to the absorption capacity obtained in this article, it can provide a planning reference capacity for the new energy grid connection to a greater extent, and meet the construction needs under the background of the current vigorous promotion of new energy.

[0110] The above embodiments and descriptions are only for illustrating the principles and best embodiments of the present invention. Without departing from the spirit and scope of the present invention, the present invention may be subject to various changes and improvements, all of which fall within the scope of the present invention to be protected.

Claims

1. A method for evaluating the new energy absorption capacity of distribution networks based on load simultaneity rate. It is characterized in that The following steps are involved: S1), collect historical data and grid information of the 10kV distribution network area, with the collection point time interval being 15 minutes; the collected historical data includes the regional total load data and new energy output data for the past year; the collected grid information includes the regional distribution network topology, line impedance and the length of each trunk branch; S2), normalize the historical data collected in step S1) to obtain the characteristic curve of total load and new energy output; specifically: S201), firstly, according to the load data of the past year, the characteristic curve of the regional overall load and the output of new energy is calculated, and the relevant calculation is as follows: Where P z (t) and P xny (t) are the total load characteristics and new energy output characteristics of the region at time t; P z ,i (t) and P xny ,i (t) are the total load and renewable energy output at time t on day i in the past year; S202), then normalize the total load characteristics and the new energy output characteristics. Since the data collection time interval is 15 minutes, there are 96 data points collected in one day, so the normalization is as follows: Where P * (t) is the load / output normalized value at time t; P(t) is the load value / output at time t; P max and P min They are the maximum load / output and minimum load / output in a day respectively; S3), establishing a power flow calculation topology grid according to the grid information collected in step S1); S4) Establish a relationship model between new energy consumption capacity and new energy output; the details are as follows: S401), the absorption capacity refers to the capacity of the distribution network that allows the construction of new energy equipment, the unit is kW, and the regional absorption capacity is P xiao , the new energy output allowed to be carried at time t is P xiao (t), then P xiao and P xiao (t) satisfies the following relationship: Where P xiao is the minimum value of renewable energy output that can be absorbed at each time of the day; P xny (t) is the output amplitude of new energy; Normalize the output value of new energy; S5) Use the binary cycle approximation method to obtain the maximum absorption capacity of the power grid for new energy; the details are as follows: S501), initialize three absorption capacities, including large, medium and small values ​​P xiao，1 , P xiao ,2 and P xiao，3 ,in, P jie，1 ＝0， P jie，3 , should be achieved greatly, P jie ,2 =(P jie ,1 +P jie ,3 ) / 2; The original total load of each node of the grid is calculated as follows: Where P k (t) is the original total load of the kth node at time t; P z (t) is the total load of the distribution network; K is the number of load nodes; S502), the absorption capacity is the capacity of a node that allows the addition of new energy sources. The output amplitudes brought by the addition of new energy sources are calculated according to the three absorption capacities. The output amplitudes corresponding to the small, medium and large absorption capacities are: Assume that the node where the new energy source is connected is node m, then the load input for the power flow calculation of node m is: P m (t)-P xny (t); Among them, P * xny (t) is the normalized value of the new energy output, P m (t) is the original total load of node m at time t; S503), under the three absorption capacities, calculate the power flow at each moment in a day, and obtain the maximum feeder current I under the three absorption capacities in a day 1 ,max ,I 2 ,max ,I 3 ,max , and the maximum voltage per unit value U of all nodes in a day 1 ,max ,U 2 ,max ,U 3 ,max ; S504) Make an over-limit judgment. Under a certain absorption capacity, if the power flow result satisfies that the maximum current exceeds the feeder current carrying capacity, or the maximum node voltage is greater than the upper limit of the voltage, it means that the absorption capacity will cause unsafe operation of the distribution network and should be reduced. The relevant over-limit formulas for current and voltage are as follows: I max >I lim ; IN max >1.07U N ; In the formula, I lim U is the current carrying capacity of the feeder; N is the voltage reference value; S505) The regional power flow results of the three absorption capacities are judged to be over-limit. If the voltage or current exceeds the limit, it is marked as 1, and if not, it is marked as 0. Thus, the over-limit situation r under the absorption capacity of small, medium and large is obtained. 1 , r 2 , r 3 ; S506) Update the small, medium and large values ​​of the absorption capacity according to the over-limit situation and by using the dichotomy method. The updating method is as follows: If r 1 =0,r 2 =0,r 3 =1, indicating that the small median value does not exceed the limit, and the large value exceeds the limit, then the original median absorption capacity needs to be assigned to the small value, and the large value absorption capacity remains unchanged. The median absorption capacity is the mean value after the large and small values ​​are updated, as shown in the following formula: S507), repeat step S2) with the updated absorption capacity until the absorption capacity accuracy is less than 10 -4 , then the final distribution network area absorption capacity Pxiao,2 is output, and the absorption capacity accuracy ε is calculated as follows: e=P xiao ,2 -P xiao ,1。

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