Power distribution network homogeneity planning method under new power system distributed photovoltaic access

Abstract

The application discloses a power system distributed photovoltaic access under the power distribution network homogeneity planning method, including the homogeneity analysis model based on the source load prediction result and the power distribution network planning model based on the homogeneity, the homogeneity analysis model based on the source load prediction result is based on the existing source load prediction result to the existing network calculation structure homogeneity index and the current-carrying homogeneity index, and the output thereof, the power distribution network planning model based on the homogeneity is to the structure homogeneity index and the current-carrying homogeneity index of the to-be-planned model as input, under the given substation configuration and layout, the total operation economic cost is lowest as the target to the distribution network planning, the planning result is output, the purpose of comprehensively considering the operation safety and the economy of the distribution network is achieved, so as to solve the problem that the fluctuation and the uncertainty of the existing planning model are not considered multiple source loads and the influence on the operation of the distribution network.

Description

[Technical field]

[0001] The present invention relates to the field of distribution network planning, and in particular to a distribution network uniformity planning method under distributed photovoltaic access in a new power system. [Background Technology]

[0002] Under the background of new power system, a large number of distributed new energy and diversified loads are connected to the distribution network, and the operation structure of the distribution network has changed. The traditional single radial type has become a two-way flow. The complexity of the interaction between the diversified loads and the power grid also causes the distribution network to be in a constantly changing state in time and space. In the traditional distribution network planning method, the basic point of view is from the perspective of economic cost, with the minimum total investment cost as the planning goal, and the substation layout and line construction are planned, without considering the impact of the volatility and uncertainty of the multiple sources and loads on the operation safety of the distribution network. The uneven distribution of distributed power sources and diversified loads in time and space has brought about the unevenness of the grid structure and grid current. It is unreasonable to ignore the uniformity of the distribution network when planning the distribution network of the new power system. This is because: (1) The uniformity of the distribution network is poor, and many equipment are running in a light-load state, with low utilization and low economic benefits. Some equipment is running under heavy load, which affects its service life and operation reliability, and there are safety hazards. (2) The uniformity of the distribution network is poor, so there must be weak links. Once the weak links are attacked, it is easy to cause a chain reaction and evolve into a major accident. (3) The new power system contains a large number of multiple sources and loads, and the interaction between sources and loads is enhanced. They influence each other and have complex characteristics of interaction with the power grid. The randomness and uncertainty in time and space make the weak links of the non-uniform power grid more vulnerable to attack and more prone to over-limit or failure. Improving the uniformity of the distribution network means improving the overall robustness of the distribution network, improving the overall utilization of the system, and improving the ability of the distribution network to cope with the uncertainty and randomness brought about by the access of multiple sources and loads in the context of the new power system. Therefore, it is necessary to incorporate normalization into the planning of the distribution network and improve the adaptability of the distribution network to the access of multiple sources and loads. [Summary of the invention]

[0003] The purpose of the present invention is to propose a distribution network uniformity planning method under the background of a new power system in response to the problem that existing planning methods are not adaptable to the new power system. By comprehensively considering the economy and uniformity of the distribution network, a win-win goal of distribution network economy and operation is achieved, providing guidance for distribution network planning.

[0004] To achieve the above object, the present invention adopts the following technical solutions:

[0005] A distribution network uniformity planning method under distributed photovoltaic access in a new power system is characterized by comprising a uniformity analysis model based on source-load prediction results and a distribution network planning model based on uniformity, wherein the two models iterate each other to obtain a distribution network planning result.

[0006] The distribution network uniformity planning method under the distributed photovoltaic access of the new power system as described above is characterized by: the uniformity analysis model based on the source-load prediction result is based on the existing source-load prediction result to calculate the uniformity index of the existing network structure and the current uniformity index; the source-load prediction result is the maximum source-load prediction result of the planning area, the power source node has the maximum predicted output value, and the load node has the maximum predicted load value.

[0007] The above-mentioned new power system distributed photovoltaic access distribution network uniformity planning method is characterized by: the structural uniformity index is based on the node importance analysis of the uniformity of the distribution network topology structure, as shown in formula (8):

[0008]

[0009] Where, E is the structural uniformity of the distribution network, E1 is the standard deviation of the importance of each node in the distribution network, E2 is the range of the importance of each node in the distribution network, N is the number of nodes in the distribution network, and I i is the node importance of node i, is the average importance of distribution network nodes.

[0010] The distribution network uniformity planning method under the distributed photovoltaic access of the new power system as described above is characterized by: the current uniformity index is based on the network flow analysis of the uniformity of the distribution network line current, as shown in formula (9),

[0011]

[0012] Where H is the structural uniformity of the distribution network, H1 is the standard deviation of the load rate of the distribution network lines, H2 is the range of the load rate of each line in the distribution network, l is the number of distribution network lines, and p is ij is the load rate of line ij, is the average value of the distribution network line load rate.

[0013] The above-mentioned new power system distributed photovoltaic access distribution network uniformity planning method is characterized by: the line load rate can be determined by formula (10):

[0014]

[0015] Where P ij is the active power passing through line i, P ijmax is the maximum allowable active power of line ij.

[0016] The distribution network uniformity planning method under the distributed photovoltaic access of the new power system as described above is characterized by: the distribution network planning model based on uniformity is a planning model that aims at minimizing the total economic cost of operation under given substation configuration and layout, and meets the flow constraints and safety constraints.

[0017] The above-mentioned new power system distributed photovoltaic access distribution network uniformity planning method is characterized by: the total operating economic cost, which is based on the investment cost, the structural uniformity and the current uniformity as the power, as shown in formula (11):

[0018]

[0019] In the formula, C inv is the investment cost, c L 、c S is the investment cost per unit length / capacity of the line and distribution transformer, is a binary investment variable for lines and distribution transformers. If the value is 1, it means that investment is needed. are the corresponding line length and distribution transformer expansion capacity, Ψ L ,Ψ S is the set of all network lines and substations, κ L , κ S It is the cost recovery factor of line and distribution transformer investment.

[0020] The above-mentioned new power system distributed photovoltaic access distribution network uniformity planning method is characterized by: the cost recovery coefficient of line and distribution transformer investment can be determined by formula (12):

[0021]

[0022] In the formula, r in is the annual discount rate; T L , T S It is the service life of the line and distribution transformer.

[0023] The distribution network uniformity planning method under the new power system distributed photovoltaic access as described above is characterized by: the power flow constraint is as shown in formula (13):

[0024]

[0025] Where P G,i , Q G,i is the active and reactive power output by the generator at node i, P G,i,min , P G,i,max , Q G,i,min , Q G,i,max The upper and lower limits of the generator capacity.

[0026] The distribution network uniformity planning method under the new power system distributed photovoltaic access as described above is characterized by: the safety constraint is as shown in formula (14)

[0027] U i,min <|U i|<U i,max (7)

[0028] Where U i is the voltage at node i; U i,min , U i,max are the upper and lower limits of the node i voltage.

[0029] The beneficial effects of the present invention are:

[0030] 1. The planning method of the present invention not only takes into account the economic indicators of building a distribution network, but also takes into account the uniformity indicators of the distribution network, taking into account both the economy and operation of the distribution network. The planned scheme has a higher overall robustness and is more in line with the requirements for economical and efficient operation of the power system.

[0031] 2. The planning method of the present invention improves equipment utilization and service life from the perspective of grid uniformity, and effectively alleviates the problem of equipment aging.

[0032] 3. The planning method of the present invention takes into account the uncertainty and randomness problems brought about by the access of multiple sources and loads in the context of the new power system, and improves the distribution network's ability to cope with the uncertain fluctuations brought about by the large-scale access of multiple sources and loads from the perspective of improving the uniformity of the power grid. [Drawings]

[0033] Figure 1 This is a flow chart of the distribution network uniformity planning method under the new type of power system distributed photovoltaic access proposed by the present invention;

[0034] Figure 2 It is the topology diagram of IEEE 4-node distribution network;

[0035] Figure 3 This is the topological diagram of the distribution network planning results. [Specific implementation method]

[0036] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the accompanying drawings.

[0037] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly. In addition, the descriptions of "preferred", "sub-preferred", etc. in the present invention are only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of indicated technical features. Therefore, the features defined as "preferred" or "sub-preferred" may explicitly or implicitly include at least one such feature.

[0038] like Figure 1As shown in the figure, a distribution network uniformity planning method under distributed photovoltaic access in the new power system includes a uniformity analysis model based on source-load prediction results and a distribution network planning model based on uniformity. The two models iterate each other to obtain the distribution network planning results, quantify the distribution network uniformity, and take into account both the distribution network uniformity and the investment cost. This overcomes the problem that the current distribution network planning method only considers the investment cost but ignores the impact of the randomness and volatility of multiple sources and loads accessing the distribution network on the operation of the power grid, and realizes the distribution network planning with a large number of multiple sources and loads accessed under the new power system.

[0039] Specifically, the uniformity analysis model based on the source-load prediction results calculates the structure uniformity index and the current-carrying uniformity index of the existing network based on the existing source-load prediction results, and proposes quantitative indicators of distribution network uniformity from the two perspectives of topological characteristics and electrical characteristics, reflecting the ability of the distribution network to cope with the randomness and volatility of multiple source loads; further, a distribution network structure uniformity index is proposed based on the distribution network topological structure, and a distribution network current-carrying uniformity index is proposed based on the distribution network operation trend, reflecting the distribution network uniformity from the two perspectives of topological characteristics and electrical characteristics.

[0040] Specifically, the source load prediction result is the maximum source load prediction result of the planning area, the value of the power source node is the maximum predicted output value, and the value of the load node is the maximum predicted load value.

[0041] Specifically, the structural uniformity index analyzes the uniformity of the distribution network topology structure based on the node importance, as shown in formula (8):

[0042]

[0043] Where, E is the structural uniformity of the distribution network, E1 is the standard deviation of the importance of each node in the distribution network, E2 is the range of the importance of each node in the distribution network, N is the number of nodes in the distribution network, and I i is the node importance of node i, and I is the average importance of distribution network nodes.

[0044] Specifically, the current uniformity index is based on the network flow analysis of the uniformity of the current of the distribution network line, as shown in formula (9):

[0045]

[0046] Where H is the structural uniformity of the distribution network, H1 is the standard deviation of the load rate of the distribution network lines, H2 is the range of the load rate of each line in the distribution network, l is the number of distribution network lines, and p is ij is the load rate of line ij, is the average value of the distribution network line load rate.

[0047] Specifically, the line load rate can be determined by formula (10):

[0048]

[0049] Where P ij is the active power passing through line i, P ijmax is the maximum allowable active power of line ij.

[0050] Specifically, the distribution network planning model based on uniformity is a planning model that aims to minimize the total economic cost under given substation configuration and layout, and meets the flow constraints and safety constraints. Based on the uniformity index of the distribution network, a planning scheme with the lowest total economic cost is obtained to achieve a win-win situation for distribution network operation and economy.

[0051] Specifically, the total operating economic cost is based on the investment cost and the structural uniformity and current uniformity as powers, as shown in formula (11):

[0052]

[0053] In the formula, C inv is the investment cost, c L 、c S is the investment cost per unit length / capacity of the line and distribution transformer, is a binary investment variable for lines and distribution transformers. If the value is 1, it means that investment is needed. are the corresponding line length and distribution transformer expansion capacity, Ψ L ,Ψ S is the set of all network lines and substations, κ L , κ S It is the cost recovery factor of line and distribution transformer investment.

[0054] Specifically, the cost recovery coefficient of line and distribution transformer investment can be determined by formula (12):

[0055]

[0056] In the formula, r in is the annual discount rate; T L , T S It is the service life of the line and distribution transformer.

[0057] Specifically, the power flow constraint is as shown in formula (13):

[0058]

[0059] Where P G,i , Q G,i is the active and reactive power output by the generator at node i, P G,i,min , P G,i,max , Q G,i,min , Q G,i,max The upper and lower limits of the generator capacity.

[0060] Specifically, the safety constraint is as shown in formula (14):

[0061] U i,min <|U i |<U i,max (14)

[0062] Where U i is the voltage at node i; U i,min , U i,max are the upper and lower limits of the node i voltage.

[0063] This embodiment is used to plan the IEEE 4-node distribution network. The topology diagram is as follows: Figure 2 shown.

[0064] The input calculation data include: IEEE 3-node distribution network data, new substation layout, and investment cost per unit length of line. L = 1,002,750 yuan / km, investment cost per unit capacity of power distribution c S = 15.0725 million yuan / km, annual discount rate r in =0.01; service life of the line T L =50 years, the service life of the transformer is T S = 30 years, maximum allowable structural uniformity E max =10, maximum allowable current uniformity H max =10, the source load prediction results are shown in Table 1.

[0065] Table 1 Maximum load data of distribution network

[0066] node Maximum load(MW) 1 50 2 170 3 200 4 80

[0067] According to the content of the invention, the planning result is: two new lines need to be built, from node 1 to node 5 and from node 3 to node 5, and the capacity of the new substation is 100MW. Figure 3 shown.

[0068] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings under the inventive concept of the present invention, or directly or indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A distribution network uniformity planning method for a new type of power system with distributed photovoltaic access, characterized by: It includes a uniformity analysis model based on source-load prediction results and a distribution network planning model based on uniformity. The two models iterate each other to obtain the distribution network planning results.

2. The method for planning uniformity of distribution network under distributed photovoltaic access in a new type of power system according to claim 1 is characterized by: The uniformity analysis model based on source-load prediction results calculates the uniformity index of the existing network structure and the current uniformity index based on the existing source-load prediction results; the source-load prediction result is the maximum source-load prediction result of the planning area, the power node value is the maximum predicted output value, and the load node value is the maximum predicted load value.

3. The method for planning uniformity of distribution network under distributed photovoltaic access in a new type of power system according to claim 2 is characterized by: The structural uniformity index analyzes the uniformity of the distribution network topology based on the node importance, as shown in formula (1): Where, E is the structural uniformity of the distribution network, E1 is the standard deviation of the importance of each node in the distribution network, E2 is the range of the importance of each node in the distribution network, N is the number of nodes in the distribution network, and I i is the node importance of node i, is the average importance of distribution network nodes.

4. The method for planning uniformity of distribution network under distributed photovoltaic access in a new type of power system according to claim 2 is characterized by: The current uniformity index is based on the network flow analysis of the uniformity of the distribution network line current, as shown in formula (2): Where H is the structural uniformity of the distribution network, H1 is the standard deviation of the load rate of the distribution network lines, H2 is the range of the load rate of each line in the distribution network, l is the number of distribution network lines, and p is ij is the load rate of line ij, is the average value of the distribution network line load rate.

5. The method for planning uniformity of distribution network under distributed photovoltaic access in a new type of power system according to claim 4 is characterized by: The line load rate can be determined by formula (3): Where P ij is the active power passing through line i, P ijmax is the maximum allowable active power of line ij.

6. The method for uniformity planning of distribution network under distributed photovoltaic access in a new type of power system according to claim 1 is characterized by: The distribution network planning model based on uniformity is a planning model that aims to minimize the total economic cost and meet the power flow constraints and safety constraints under given substation configuration and layout.

7. The method for planning uniformity of distribution network under distributed photovoltaic access in a new type of power system according to claim 6 is characterized by: The total economic cost of operation is based on the investment cost and the structural uniformity and current uniformity as the power, as shown in formula (4): In the formula, C inv is the investment cost, c L 、c S is the investment cost per unit length / capacity of the line and distribution transformer, is a binary investment variable for lines and distribution transformers. If the value is 1, it means that investment is needed. are the corresponding line length and distribution transformer expansion capacity, Ψ L , S is the set of all network lines and substations, κ L , κ S It is the cost recovery factor of line and distribution transformer investment.

8. The method for planning uniformity of distribution network under distributed photovoltaic access in a new type of power system according to claim 7 is characterized by: The cost recovery coefficient of line and distribution transformer investment can be determined by formula (5): In the formula, r in is the annual discount rate; T L , T S It is the service life of the line and distribution transformer.

9. The method for planning uniformity of distribution network under distributed photovoltaic access in a new type of power system according to claim 6 is characterized by: The power flow constraint is shown in formula (6): Where P G,i , Q G,i is the active and reactive power output by the generator at node i, P G,i,min , P G,i,max , Q G,i,min , Q G,i,max The upper and lower limits of the generator capacity.

10. The method for uniformity planning of distribution network under distributed photovoltaic access in a new type of power system according to claim 6 is characterized by: The safety constraint is shown in formula (7): IN i,min <|U i |<U i,max (7) Where U i is the voltage at node i; U i,min , U i,max are the upper and lower limits of the node i voltage.

Images