Transformer substation pre-disaster emergency resource allocation method based on transmission and distribution cooperation under flood disaster

Abstract

The invention discloses a transformer substation pre-disaster emergency resource allocation method based on transmission and distribution collaboration under flood, and belongs to the field of power systems, and the method comprises the steps: obtaining the historical flood data of each transformer substation in a power system, and generating a flood depth probability density curve according to the historical flood data of each transformer substation; before the flood disaster occurs, the rainfall capacity is predicted; the flood depth, the fault probability, the expected economic loss and the expected maintenance time of the transformer substation are speculated by analyzing the flood depth probability density curve of the transformer substation; calculating a characteristic value of the transformer substation through the load capacity of the transformer substation, the expected maintenance time and the expected economic loss; establishing a two-dimensional space by taking the substation fault probability as an abscissa and the characteristic value of the substation as an ordinate, and generating a flood fault scene; a pre-disaster-based transformer substation emergency resource allocation model is established, and before a flood disaster occurs, a key transformer substation is selected to install a dam by taking the minimum economic loss of the transformer substation as a target so as to protect the transformer substation.

Description

Technical Field

[0001] The present invention belongs to the field of power systems, and more specifically, relates to a pre-disaster emergency resource allocation method for substations based on transmission and distribution coordination during floods. Background Art

[0002] Among natural disasters, flooding poses the most costly threat to power systems due to loss of life and component damage. Power systems in low-slope coastal areas are more vulnerable to flooding. Flooding can damage power system assets, particularly substations, which are among the most expensive and critical components. Substation outages can significantly reduce the resilience of the grid and lead to widespread, prolonged power outages. Taking preventative measures before a flood occurs is necessary to mitigate its impact. Current methods for substation infrastructure reinforcement primarily involve installing the substation on an elevated foundation slab and installing permanent physical barriers. These methods are permanent, long-term plans that require time and improvement through the implementation of operational resilience actions. Tiger Dam, a flood control system around a substation, is a temporary but effective substation protection solution.

[0003] Power system resilience refers to the ability of a power system to prevent, resist, adapt, and quickly recover from emergencies such as natural disasters and man-made sabotage. Improving power system resilience not only reduces losses caused by disasters but also ensures the normal operation of society and stable economic development. Improving power system resilience is particularly important during extreme weather events such as floods. By strengthening the power system's disaster resistance, optimizing emergency response mechanisms, and increasing recovery speed, the impact of floods on the power system can be effectively reduced, ensuring the continuity and reliability of power supply. Therefore, improving power system resilience has become a critical issue in the current power industry. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to propose a pre-disaster emergency resource allocation method for substations based on transmission and distribution coordination under floods. It is a flood control power system resilience improvement method based on emergency resource allocation. By rationally allocating the Tiger Dam installation team resources in the two-level transmission and distribution power grids, and considering the output characteristics of the generator sets in the transmission and distribution power grid, the key substations that need to be protected are determined, the impact of floods on substations is reduced, and the continuity and reliability of power supply are guaranteed.

[0005] To achieve the above objectives, the present invention provides a method for pre-disaster emergency resource allocation of substations based on transmission and distribution coordination during floods, comprising:

[0006] Obtain the historical flood data of each substation in the power system. Since the probability density curve of the flood depth of the substation follows a logarithmic distribution, generate the probability density curve of the flood depth based on a small amount of historical flood data for each substation;

[0007] Before the flood disaster occurs, predict the rainfall to obtain the expected rainfall;

[0008] Speculate the flood depth, failure probability, expected economic loss, and expected maintenance time of the substation by analyzing the probability density curve of the flood depth of the substation;

[0009] To simplify the calculation complexity, divide the substations into affected substations and unaffected substations according to the predicted expected rainfall, and subsequent protection decisions are only for the affected substations;

[0010] Generate representative flood failure scenarios based on the historical flood data of the substation and the expected rainfall;

[0011] Establish a two-dimensional space with the substation failure probability as the abscissa and the characteristic value of the substation as the ordinate to generate flood failure scenarios;

[0012] Establish a pre-disaster substation emergency resource allocation model. Before the flood disaster occurs, with the goal of minimizing the economic loss of the substation, select key substations to install tiger dams to protect the substations;

[0013] The pre-disaster substation emergency resource allocation model is as follows:

[0014]

[0015] where k rs and k ds are the states of the transmission network and distribution network substations at time t in the flood failure scenario s respectively; β r and β d are the relevant costs of the transmission network substation r and the distribution network substation d respectively; L is is the load reduction of the distribution network connected to the transmission network node i in the flood failure scenario s; e is the economic value corresponding to the unit load;

[0016] Constraint conditions:

[0017]

[0018]

[0019] 0 ≤ p i,t ≤ P i,t

[0020] 0 ≤ q i,t≤Q i,t

[0021]

[0022]

[0023] where p gst represents the output of the generator at time t in the flood fault scenario s; p gst-1 represents the output of the generator at time t - 1 in the flood fault scenario s; k gs represents the availability of the substation connected to the node where the generator g is located under the flood fault scenario s; and represent the upper and lower limits of the generator output respectively; RU g and RD g represent the upper and lower ramping limits respectively; k ls represents the availability of line l in the flood fault scenario s; k los and k lds represent the availabilities of the substations at the beginning and end of line l respectively; f lst represents the transmission power of line l at time t in the flood fault scenario s; f l max represents the maximum capacity allowed to flow through line l; M is to ensure that when the line is unavailable, the transmission power is independent of the voltage angle; B l represents the susceptance of line l; Δδ st represents the difference in voltage phase angles at the beginning and end of the line in the flood fault scenario s; Ω i represents the set of distribution networks connected to the transmission network node i; p ist represents the power curtailment at the transmission network node i in the flood fault scenario s; represents the load at the transmission network node i at time t; represents the load at the transmission network node i at time t; represents the power transmitted from the transmission network node i to the distribution network under the flood fault scenario s; P DGjt and Q DGjt are the active and reactive power outputs of the distributed power source connected to node j at time t respectively; P ij,t and Q ij,t are the active and reactive power flowing through line ij at time t respectively; P jk,t and Q jk,t are the active and reactive power flowing through line jk at time t respectively; P j,t and Q j,t are the active and reactive power of the load at node j at time t respectively; r ij and x ij are the resistance and reactance of line ij; pj,t and q j,t are the active and reactive load curtailments of node j at time t, respectively; U i,t is the voltage of node i at time t; I ij,t is the square of the current flowing through line ij at time t; u(j) is the set of the first-section nodes of the branches with the end node j; w(j) is the set of the end nodes of the branches with the first node j; k rs and k ds are the states of the transmission network and the distribution network substation at time t under the flood fault scenario s, respectively; represents the load of the distribution network connected to distribution network substation d at time t; p dist represents the sum of the load curtailments of distribution network substation d connected to transmission network node i; T is the total available time for implementing protection actions; N team is the number of flood control protection teams; unkt is a binary variable dispatched by flood control protection team n of the substation; τ k is the protection time of the substation; the binary variable b k indicates whether to protect the substation; ∈ is a very small positive number; o nkt is an auxiliary binary variable that forces the number of teams dispatched to the substation location to be at most one.

[0024] Furthermore, the substation failure probability determination process is as follows:

[0025] Divide the flood depth probability density function g k of substation k into several intervals; the i-th interval is expressed as [h i , h i+1 , where h i and h i+1 represent the flood depths at both ends of the interval, respectively. Each interval corresponds to a flood fault scenario; for each flood fault scenario, its representative flood depth is taken as the average of the interval endpoints (h i +h i+1 ) / 2. Calculate the probability of the occurrence of the predetermined flood depth through the probability density function g k , and the expression is:

[0026]

[0027] where, represents the probability that substation k encounters a flood depth of (h i +h i+1 ) / 2;

[0028] The overall failure probability of the substation is obtained by the weighted sum of the probabilities of each flood fault scenario and their corresponding failure probabilities. The specific expression is:

[0029]

[0030] Among them, π k is the failure probability of substation k; is the failure probability of substation k under the flood failure scenario s with a flood depth of (h i +h i+1 ) / 2.

[0031] Furthermore, the expected economic loss of the substation is determined as follows:

[0032] Establish the relationship between the flood depth and the degree of substation damage, and the expression is:

[0033]

[0034] where h ki represents the flood depth of substation k under the flood failure scenario; d ki represents the degree of damage of substation k at the flood depth h ki .

[0035] The expected degree of damage of substation k is:

[0036]

[0037] In the formula, D k represents the percentage of substation k damaged by the flood;

[0038] The expected economic loss of the substation is:

[0039]

[0040] where DC k is the expected economic loss of substation k, and P k is the cost of substation k.

[0041] Furthermore, define the concept of the eigenvalue of the substation. This eigenvalue comprehensively considers factors such as the expected repair time, the expected economic loss, the load capacity, and the importance of the load. The specific expression is;

[0042]

[0043] where, ω kd is the weight of the load, is the load quantity on substation k; t k is the expected repair time of substation k; DC k is the expected economic loss of substation k; c kIt represents the importance level of the loads connected to substation k, which is determined by the weights of the first-level, second-level, and third-level loads connected to the substation respectively accounting for the total load; the weighting factors A, B, C, and D represent the importance levels of the four items of load quantity, maintenance time, expected economic loss, and the importance of the connected loads respectively, and A + B + C + D = 100%.

[0044] Furthermore, the failure probability π of the substation under flood disasters ks is the benchmark failure probability π generated from historical data k and is determined by the intensity of rainfall. The specific expression is as follows:

[0045]

[0046] wherein, R represents the expected rainfall depth within 12 hours, and R h represents the benchmark value of the rainfall depth within 12 hours.

[0047] Through the above design scheme, the present invention can bring the following beneficial effects:

[0048] 1. Through the coordinated operation of the transmission network and the distribution network, the optimal allocation of resources and the rapid isolation of faults are realized, the overall resilience of the system is improved, and the power outage time and scope are reduced.

[0049] 2. In extreme events (such as floods), the power system is prone to cascading failures, resulting in large-scale power outages. After the dispatching instructions are issued, the overall allocation of resources and the zonal coordination are realized to ensure the stability of the system operation.

[0050] 3. The method proposed by the present invention reduces the economic losses caused by floods to the substation by allocating emergency resources of the substation before the disaster. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] The following drawings are used to provide a further understanding of the present invention, and constitute a part of the present invention application. The schematic embodiments of the present invention and their descriptions are used to understand the present invention, and do not constitute an improper limitation of the present invention. In the drawings:

[0052] Figure 1 is the flow chart of the substation emergency resource scheduling decision;

[0053] Figure 2 is the simplified method diagram of the substation flood failure scenario;

[0054] Figure 3 is the IEEE 24-node and the coupled distribution network topology diagram;

[0055] Figure 4 is the schematic diagram of the substation flood control protection team scheduling decision in Scenario 1;

[0056] Figure 5 It is a schematic diagram of the dispatching decision-making of the substation flood control protection team in Scenario 2. Specific implementation manner

[0057] The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit scope of the technical solution of the present invention shall be covered within the protection scope of the present invention.

[0058] As Figure 1 shown, the method for pre-disaster emergency resource allocation of substations based on transmission and distribution coordination under flood disasters proposed by the present invention includes:

[0059] I. Obtain the historical flood data of each substation in the power system. Since the flood depth probability density curve of the substation follows a logarithmic distribution, the flood depth probability density curve of the substation is generated based on a small amount of historical flood data of each substation; before the flood disaster occurs, predict the rainfall amount to obtain the expected rainfall amount; and infer the flood depth, failure probability, expected economic loss, and expected maintenance time of the substation by analyzing the probability density curve of the substation flood depth.

[0060] 1) Substation flood depth probability density function

[0061] Due to geographical location differences, the flood risk levels faced by substations in the transmission and distribution network vary significantly. The main factors affecting the degree of flood damage to substations include: the structural characteristics of the substation, the site altitude, and the intensity and duration of local rainfall. Therefore, it is clearly not in line with the actual situation to analyze all substations under the same flood failure scenario. To more accurately describe the flood risk of each substation, the present invention uses a probability density function to predict the flood depth of the substation. Research shows that the probability density function of the substation flood depth conforms to a lognormal distribution. By analyzing the historical flood data of each substation, the flood depth probability density function g k of a specific substation can be obtained.

[0062] 2) Substation failure probability

[0063] The present invention divides the flood depth probability density function g k of substation k into several intervals. The i-th interval is expressed as [h i , h i+1 , where h i and h i+1 respectively represent the flood depths at both ends of the interval. Each interval corresponds to a specific flood failure scenario. For each flood failure scenario, the representative flood depth is taken as the average of the interval endpoints (h i + h i+1) / 2, through the probability density function g k Calculate the probability of a specific flood depth occurring, and the expression is as shown in Equation (1):

[0064]

[0065] Where Represents the probability that substation k encounters a flood depth of (h i +h i+1 ) / 2.

[0066] The vulnerability curve of the substation describes the relationship between the flood depth and the substation failure probability. Based on the vulnerability curve of the substation, the failure probability of the substation under each flood failure scenario can be determined. The overall failure probability of the substation can be obtained by the weighted sum of the probabilities of each flood failure scenario and their corresponding failure probabilities, and the specific calculation is as shown in Equation (2):

[0067]

[0068] Where π k Is the failure probability of substation k; Is the failure probability of substation k under the flood failure scenario s with a flood depth of (h i +h i+1 ) / 2.

[0069] 3) Expected economic loss of the substation

[0070] The present invention uses the substation loss curve to evaluate the damage degree of the substation under different flood failure scenarios. Based on the substation loss curve provided by the Federal Emergency Management Agency (FEMA) of the United States, establish the relationship between the flood depth and the damage degree of the substation, and the expression is as shown in Equation (3):

[0071]

[0072] Where, h ki Represents the flood depth of substation k under the flood failure scenario; d ki Represents the damage degree of substation k at the flood depth h ki Below.

[0073] Table 1 Substation costs at each voltage level

[0074]

[0075] Then the expected damage degree of substation k is:

[0076]

[0077] In the formula, D kIndicates the percentage of the substation k damaged by floods.

[0078] The expected economic loss of the substation is:

[0079]

[0080] Where DC k is the expected economic loss of substation k, and P k is the cost of substation k, which is mainly determined by the voltage level where the substation is located, as shown in Table 1.

[0081] The expected repair time of the substation is closely related to its damage degree. Through the expected repair time - damage degree curve of the substation, according to the expected damage percentage D k the repair time of substation k can be accurately estimated.

[0082] 4) Simplification method for substation flood fault scenarios

[0083] Due to the high uncertainty of floods, the prediction and modeling of their depth are extremely complex, and it is difficult for grid operators to obtain accurate flood information. Therefore, China's power grid usually adopts the random scenario method to formulate protection strategies based on the possible power outages of substations. In each flood fault scenario, the substation only has two mutually exclusive states: failure (represented by "1") and normal operation (represented by "0"). Among them, F ds and F rs respectively represent whether the substation d of the distribution network and the substation r of the transmission network fail in the flood fault scenario s without installing Tiger Hum. Theoretically, 2 N scenarios can be generated for N substations (N is the total number of substations). However, considering that the occurrence probability of some scenarios is extremely low and to reduce the computational complexity, the present invention adopts a scenario simplification method to simplify the substation flood fault scenarios into a set of representative scenarios.

[0084] To quantify the importance of substations to the power grid, the present invention proposes the concept of substation eigenvalue, as shown in Equation (6). This eigenvalue comprehensively considers factors such as expected repair time, expected economic loss, load capacity, and the importance of the load. For grid operators, substations with larger loads, serving important users, longer repair times, and larger potential economic losses should be protected first.

[0085]

[0086] Among them, ω kd is the weight of the load, is the load amount on substation k; t k is the expected repair time of substation k; DC k is the expected economic loss of substation k; ck Indicates the importance level of the loads connected to substation k, which is determined by the weights of the first-class, second-class, and third-class loads connected to the substation respectively accounting for the total load; the weighting coefficients A, B, C, and D represent the importance levels of the four items of load quantity, maintenance time, expected economic loss, and the importance of the connected loads respectively (A + B + C + D = 100%).

[0087] The failure probability π of the substation under flood disasters ks is the baseline failure probability π generated from historical data k and the intensity of rainfall, as specifically shown in Equation (7).

[0088]

[0089] Among them, R represents the expected rainfall depth within 12 hours, and R h represents the baseline value of the rainfall depth within 12 hours.

[0090] The present invention constructs a two-dimensional space (as Figure 2 shown), with the failure probability π ks as the abscissa and the substation characteristic value as the ordinate. By setting multiple horizontal and vertical thresholds, several failure scenario points are formed. For each failure scenario point, the substations located on its right and above are determined to be in a failure state, and the rest are regarded as operating normally. This scenario simplification method ensures that substations with higher failure probabilities and importance levels are marked as "failed" in more scenarios, so that these key substations are given priority consideration when formulating protection strategies.

[0091] II. The present invention establishes a pre-disaster substation emergency resource allocation model. With the goal of minimizing the economic loss of the substation, a solution is provided for the power system to resist flood disasters. The model construction includes the following steps:

[0092] Construct a pre-disaster substation emergency resource allocation model:

[0093] The optimization model proposed by the present invention aims to minimize the overall economic loss caused by floods to the power grid, including the direct loss of the transmission and distribution network substations and the indirect economic loss brought by load shedding. When calculating the load shedding amount, this model innovatively uses the load shedding amount of the entire distribution network connected to the transmission network nodes to replace the traditional node power shedding amount. This method can better consider the output characteristics of distributed power sources in the active distribution network, thereby improving the effectiveness of decision-making. The objective function is expressed as:

[0094]

[0095] Among them, k rs and k dsThey are the states of the transmission network and the distribution network substation at time t in the flood fault scenario s; β r and β d are the relevant costs of the transmission network substation r and the distribution network substation d respectively; L is is the load reduction of the distribution network connected to the transmission network node i in the flood fault scenario s; e is the economic value corresponding to the unit load (MW).

[0096] The calculation formula is as follows:

[0097] β k = b k C k +(1 - b k )DC k (9)

[0098] b k is a protection variable. If the substation k is protected, the binary variable b k is 1, otherwise it is 0; C k is the cost of protecting the substation k; DC k is the loss caused by the flood to the substation. It should be noted that the formula (9) is satisfied when the substation k is the distribution network substation d or the transmission network substation r.

[0099] Constraint conditions:

[0100] a) Generator output constraint:

[0101]

[0102] Among them, equation (10) is the generator output constraint, p gst represents the output of the generator at time t in the flood fault scenario s, p gst-1 represents the output of the generator at time t - 1 in the flood fault scenario s, k gs represents the availability of the substation of the node connected to the generator g in the flood fault scenario s, and represent the upper and lower limits of the generator output; equations (11) and (12) represent the upper and lower ramping constraints of the generator output respectively; RU g and RD g represent the upper and lower ramping limits respectively.

[0103] b) Transmission network constraint:

[0104]

[0105] Among them, equation (13) represents the availability constraint of the transmission line. The availability of the line is determined by the availability of the substations at both ends of the line, k lsDenotes the availability of line l in the flood fault scenario s, k los and k lds Denote the availabilities of the substations at the beginning and end of line l respectively; Equation (14) represents the transmission capacity constraint of the line, f lst Denotes the transmission power of line l at time t in the flood fault scenario s; f l max Denotes the maximum capacity allowed to flow through line l; Equations (15) and (16) represent the power angle constraints, where M is to ensure that when the line is unavailable, the transmission power is independent of the voltage angle; B l Denotes the susceptance of line l; Δδ st Denotes the difference in voltage phase angles at the beginning and end of the line in the flood fault scenario s; Equation (17) represents the active power balance constraint; Denotes the load at time t on the transmission grid node i; p ist The amount of power reduction on the transmission grid node i in the flood fault scenario s; Ω i Denotes the set of distribution grids connected to the transmission grid node i; Denotes the load on the transmission grid node i at time t.

[0106] c) Distribution grid constraints:

[0107]

[0108]

[0109] 0 ≤ p i,t ≤ P i,t (22)

[0110] 0 ≤ q i,t ≤ Q i,t (23)

[0111] Where, P DGjt and Q DGjt Are the active and reactive power outputs of the distributed power source connected to node j at time t respectively; Denotes the power transmitted from the transmission grid node i to the distribution grid under the flood fault scenario s, P ij,t and Q ij,t Are the active power and reactive power flowing through line ij at time t respectively; P jk,t and Q jk,t Are the active power and reactive power flowing through line jk at time t respectively; P j,t and Q j,t Are the active power and reactive power of the load at node j at time t respectively; r ij and x ij Are the resistance and reactance of line ij; p j,t and q j,tare the active and reactive power curtailment amounts of node j at time t; U i,t is the voltage of node i at time t; I ij,t is the square of the current flowing through line ij at time t; u(j) is the set of the first-section nodes of the branches with the end node being j; w(j) is the set of the end nodes of the branches with the first node being j.

[0112] d) Transmission and distribution coupling constraints

[0113]

[0114]

[0115] Among them, represents the load connected to the distribution substation at time t of day d; p dist is the sum of the load curtailment amounts of the distribution network of the substation; Equation (24) indicates that the actual load amount on the transmission network node i cannot be greater than the sum of the load amounts of the distribution networks connected to this node; Equation (25) indicates that when the transmission substation on the transmission network node i fails, the loads of all the distribution networks connected to this node are lost; Equations (26) and (27) represent the power transmitted from the transmission network to the distribution network.

[0116] e) Substation flood control protection team constraints:

[0117] Before the flood comes, the management departments of each region of the transmission and distribution network need to formulate protection strategies for the substations within their jurisdiction. The formulation of protection decisions mainly considers three key factors: the number of protection teams, the task start time, and the grid topology. During the specific implementation process, only one flood control protection team can be assigned to each substation, and each flood control protection team needs to install the Tiger Dam at the current substation before it can be transferred to the next target site. To simplify the calculation, the transfer time between substations is not considered in the model.

[0118]

[0119] Among them, T is the total available time for performing protection actions; N team is the number of flood control protection teams; u nkt is a binary variable for unit scheduling; τ k is the protection time of substation k; b k indicates whether to install Tiger Hum at the substation; ∈ is a very small positive number; o nrt is an auxiliary binary variable that forces the number of teams dispatched to the substation location to be at most one.

[0120] The protection time of the substation by the substation flood control protection team depends on the average flood depth of the substation and the number of people in the protection team, as follows:

[0121]

[0122] Where: τ k is the protection time of substation k; H k is the average flood depth of substation k; N w is the number of the installation team of Hub Dam.

[0123] III. Feasibility Verification

[0124] Next, the improved IEEE 24-node power transmission network is used to verify the feasibility of the method proposed by the present invention.

[0125] 1) Scenario Setting

[0126] There are 24 power transmission network substations (T1 - T24) and 40 distribution network substations (D1 - D40) in this electronic system. The interconnection relationships of each substation are shown in Table 2 in detail. The 40 distribution network substations are altogether responsible by three power grid companies. As Figure 3 shown, specifically as shown in Table 3, not all power transmission network substations are connected to distribution network substations, and some of them are only responsible for voltage level conversion.

[0127] Table 2 Interconnection Relationship of Power Transmission and Distribution Network Substations

[0128]

[0129] Table 3 Substations Responsible by Each Power Grid Company

[0130]

[0131] In this power system, some distribution network substations (D1, D12, D15, D16, D21, D23, D32, D36) are defined as active distribution network substations. These active distribution networks integrate a small amount of distributed power sources, and their topological structures are as Figure 3 shown. In the case of power outage of the power transmission network, these distributed power sources will give priority to ensuring the power supply of important loads. The remaining 32 distribution network substations are regarded as traditional distribution network substations, and their loads will all be interrupted after the power outage of the power transmission network.

[0132] 2) Generation of Substation Flood Fault Scenarios

[0133] The substation data (including failure probability, expected damage percentage, expected economic loss and expected repair time) is derived from flood data and combined with the specific vulnerability curve, damage curve, repair time curve and cost factor of the substation. In subsequent studies, these data will be regarded as known parameters.

[0134] The calculation of substation characteristic values comprehensively considers substation load, expected maintenance time, and expected economic loss, and their weights are set to 0.5, 0.2, and 0.3 respectively. Based on the calculated characteristic values and failure probabilities of 24 transmission network substations and 40 distribution network substations, a two-dimensional spatial distribution of substations is constructed, as Figure 2 shown.

[0135] Table 4 Flood fault scenarios

[0136]

[0137] 3) Analysis of model improvement effect

[0138] To verify the feasibility of the proposed substation emergency resource scheduling model based on transmission and distribution coordination, the following two scenarios are set from different configuration perspectives.

[0139] Scenario 1: The substation information between the transmission network and the distribution network is not interconnected, and the distribution network and the transmission network formulate their own substation emergency resource scheduling strategies respectively.

[0140] Scenario 2: The substation information between the transmission network and the distribution network is interconnected, and they jointly formulate the distribution strategy of substation resources and consider the distributed power sources in the active distribution network and the topological structure of the distribution network.

[0141] Two flood protection teams are arranged in the transmission network, denoted as Team 1 and Team 2. Each of the three power grid companies in the distribution network arranges 1 flood protection team to protect the substations under their responsibility, denoted as Team 3, Team 4, and Team 5 in sequence. Each team consists of four staff members, and the protection time of each substation is calculated based on the personnel of the flood protection team and the flood depth of each substation. It is considered that the disaster information is obtained ten hours before the disaster starts, and the flood protection teams of the transmission network and the distribution network start to perform the substation flood protection task. To simplify the decision-making process, the inter-station travel time of the teams is ignored when formulating the protection strategy. The team scheduling schemes under the two scenarios are as Figure 4 and Figure 5 shown.

[0142] Table 5 Losses under each scenario

[0143]

[0144] Compared with Scenario 1, the load reduction in Scenario 2 is significantly reduced by 166.2%. Scenario 1 mainly focuses on minimizing the economic losses of substations and does not fully consider the synergy between the transmission and distribution networks. Therefore, its substation economic losses are the lowest. However, the method proposed in Scenario 2 can more effectively coordinate the resources of the transmission and distribution networks and performs best in reducing the total losses, which is 39.8% lower than that in Scenario 1. This is highly consistent with the main objective of the substation emergency resource scheduling model proposed in this paper - minimizing the total system economic losses. The results show that the model in Scenario 2 can make more effective use of existing resources, make more effective decisions, and enhance the resilience of the power system. [[ID=])]

[0145] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for pre-disaster emergency resource allocation of a substation based on the coordination of power transmission and distribution under flood disasters, characterized in that, It includes the following steps: Obtain the historical flood data of each substation in the power system, and generate the flood depth probability density curve according to the historical flood data of each substation; Before the flood disaster occurs, predict the rainfall to obtain the expected rainfall; Speculate the flood depth, failure probability, expected economic loss and expected maintenance time of the substation by analyzing the flood depth probability density curve of the substation; Calculate the characteristic value of the substation through the substation load, expected maintenance time and expected economic loss; Establish a two-dimensional space with the substation failure probability as the abscissa and the characteristic value of the substation as the ordinate to generate a flood failure scenario; Establish a pre-disaster substation emergency resource allocation model. Before the flood disaster occurs, with the goal of minimizing the economic loss of the substation, select key substations to install tiger dams to protect the substations; The pre-disaster substation emergency resource allocation model is as follows: where k rs and k ds are the states of the transmission network and distribution network substations at time t under the flood fault scenario s, respectively; β r and β d are the relevant costs of the transmission network substation r and the distribution network substation d, respectively; L is is the load reduction of the distribution network connected to the transmission network node i in the flood fault scenario s; e is the economic value corresponding to the unit load. Constraint conditions: 0 ≤ p i,t ≤ P i,t 0 ≤ q i,t ≤ Q i,t Among them, p gst represents the output of the generator at time t in the flood fault scenario s; p gst-1 represents the output of the generator at time t - 1 in the flood fault scenario s; k gs represents the availability of the substation of the node connected to the generator g under the flood fault scenario s; and represent the upper and lower limits of the generator output respectively; RU g and RD g represent the upper and lower ramp limits respectively; k ls represents the availability of line l in the flood fault scenario s; k los and k lds represent the availabilities of the substations at the start and end of line l respectively; f lst represents the transmission power of line l at time t in the flood fault scenario s; f l max represents the maximum capacity allowed to flow through line l; M is to ensure that when the line is unavailable, the transmission power is independent of the voltage angle; B l represents the susceptance of line l; Δδ st represents the difference in voltage phase angles at the beginning and end of the line in the flood fault scenario s; Ω i represents the set of distribution networks connected to the transmission network node i; pist represents the power curtailment at the transmission network node i in the flood fault scenario s; represents the load at time t on the transmission network node i; represents the load at time t on the transmission network node i; represents the power transmitted from the transmission network node i to the distribution network under the flood fault scenario s; P DGjt and Q DGjt represent the active and reactive power outputs of the distributed power source connected to node j at time t respectively; P ij,t and Q ij,t represent the active and reactive powers flowing through line ij at time t respectively; P jk,t and Q jk,t represent the active and reactive powers flowing through line jk at time t respectively; P j,t and Q j,t represent the active and reactive power loads of node j at time t respectively; r ij and x ij are the resistance and reactance of line ij; p j,t and q j,t are the active and reactive load curtailments of node j at time t respectively; U i,t is the voltage of node i at time t; I ij,t The square of the current flowing through line ij at time t; u(j) is the set of the first nodes of the branches with the end node j; w(j) is the set of the end nodes of the branches with the first node j; k rs and k ds are the states of the transmission grid and the distribution network substation at time t under the flood fault scenario s, respectively; represents the load of the distribution network connected to distribution network substation d at time t; p dist represents the sum of the load curtailment amounts of distribution network substation d connected to transmission grid node i; T is the total available time for performing protection actions; N team is the number of flood control protection teams; u nkt is a binary variable scheduled by flood control protection team n for the substation; τ k is the protection time of the substation; the binary variable b k indicates whether to protect the substation; ∈ is a very small positive number; o nkt is an auxiliary binary variable that forces the number of teams dispatched to the substation location to be at most one.

2. The pre-disaster emergency resource allocation method for a substation based on the coordination of transmission and distribution under flood disasters according to claim 1, wherein, The process of determining the substation failure probability is as follows: Divide the flood depth probability density function g of substation k k into several intervals; the i-th interval is denoted as [h i , h i+1 , where h i and h i+1 represent the flood depths at both ends of the interval respectively, and each interval corresponds to a flood fault scenario; for each flood fault scenario, its representative flood depth is taken as the average value of the interval endpoints (h i + h i+1 ) / 2. Calculate the probability of the occurrence of a predetermined flood depth through the probability density function g k , and the expression is: Among them, represents the probability that the flood depth of substation k is (h i + h i+1 ) / 2; The overall failure probability of the substation is obtained by the weighted sum of the probabilities of each flood failure scenario and their corresponding failure probabilities. The specific expression is: where, π k is the failure probability of substation k; is the failure probability of substation k under the flood failure scenario s with the flood depth of (h i + h i+1 ) / 2.

3. The method for pre-disaster emergency resource allocation of a substation based on transmission and distribution coordination under flood disasters according to claim 2, wherein, The process of determining the expected economic loss of the substation is as follows: Establish the relationship between the flood depth and the degree of substation damage. The expression is: where h ki represents the flood depth of substation k under the flood fault scenario; d ki represents the degree of damage of substation k at the flood depth h ki ; The expected degree of damage of substation k is: where D k represents the percentage of substation k damaged by flood; The expected economic loss of the substation is: Among them, DC k is the expected economic loss of substation k, and P k is the cost of substation k.

4. The method for pre-disaster emergency resource allocation of a substation based on transmission and distribution coordination under flood disasters according to claim 3, wherein, Define the concept of the substation characteristic value, which comprehensively considers factors such as the expected maintenance time, expected economic loss, load capacity and importance of the load. The specific expression is; Among them, ω kd is the weight of the load, is the load quantity on substation k; t k is the expected maintenance time of substation k; DC k is the expected economic loss of substation k; c k represents the importance degree of the load connected to substation k, which is determined by the weights of the first-level, second-level, and third-level loads connected to the substation respectively accounting for the total load; the weighting coefficients A, B, C, and D respectively represent the importance levels of the four items of load quantity, maintenance time, expected economic loss, and the importance of the connected load, and A + B + C + D = 100%.

5. The pre-disaster emergency resource allocation method for substations based on the coordination of transmission and distribution under flood disasters according to claim 4, wherein, The fault probability π of a substation under flood disasters ks is the benchmark fault probability π generated from historical data k and is determined by the intensity of rainfall. The specific expression is as follows: where R represents the rainfall depth expected within 12 hours, and R h represents the reference value of the rainfall depth within 12 hours.

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