Sectional transfer method and device for local load of power distribution network and medium

Abstract

The invention relates to the technical field of power distribution network fault recovery, in particular to a power distribution network local load segmented transfer method based on line bearing capacity evaluation and a parallel tabu search algorithm. Obtaining a power distribution network coefficient, distributed photovoltaic and energy storage equipment output, a load demand and fault position information; calculating the power flow distribution of the power distribution network after the fault occurs and before transfer by adopting a forward-backward substitution method, defining a safety margin index, and screening out a transferable safety line set; a power distribution network load transfer model fusing high voltage priority, important user priority and loss load priority is constructed, and based on a transferable safety line set, a parallel tabu search algorithm is adopted to perform optimization in a safety solution space to obtain an optimal transfer scheme; and calculating a fault rate based on the load rate of the line after transfer, and marking a high-risk line exceeding a threshold value. According to the invention, an effective load transfer scheme can be provided immediately after the power distribution network has a fault, so that the power failure loss after the fault occurs is reduced, and the user satisfaction is improved.

Description

Technical Field

[0001] This invention relates to the field of power distribution network fault recovery technology, specifically to a method, device, and medium for partial load transfer in a power distribution network. Background Technology

[0002] Fault recovery, as an important research direction in the field of power distribution networks, aims to transfer the load of the lines within the fault outage area to other distribution lines, thereby reducing the power loss caused by the fault and improving the reliability of power distribution network operation.

[0003] With the increasing penetration of distributed photovoltaic, energy storage, and other new energy equipment in distribution networks, load transfer, as a core link in the fault recovery process, has become significantly more technically challenging. On the one hand, the power flow distribution of distribution networks exhibits strong uncertainty and time-varying characteristics. Traditional load transfer methods, mostly optimized based on static network parameters and historical load curves, struggle to dynamically respond to fluctuations in new energy output and real-time load changes, leading to risks of line overload or voltage exceeding limits during actual implementation. On the other hand, existing load transfer methods often solely pursue maximizing load recovery without fully considering the coordination of key principles such as "prioritizing high-voltage lines" and "tiered protection for important users," resulting in a lack of holistic consideration in the solutions.

[0004] Therefore, there is an urgent need to develop a method for partial load transfer in distribution networks based on line carrying capacity assessment and parallel tabu search algorithm, in order to meet the fault recovery needs of distribution networks with a high proportion of new energy. Summary of the Invention

[0005] The purpose of this invention is to provide a method for partial load transfer in distribution networks based on line carrying capacity assessment and parallel tabu search algorithm: to solve the technical problems of existing schemes that are based on static network parameters and historical data for optimization, which are difficult to adapt to the increase in the penetration rate of new energy sources and difficult to achieve multi-objective collaborative optimization.

[0006] The above-mentioned objective of this application is achieved through the following technical solution:

[0007] A method for segmented load transfer in a distribution network based on line carrying capacity assessment and parallel tabu search algorithm includes the following steps:

[0008] Step 1: Obtain information on the distribution network coefficient, output of distributed photovoltaic and energy storage equipment, load demand, and fault location;

[0009] Step 2: For the distribution network topology after disconnecting the relevant disconnecting switches in the fault area, the forward-backward substitution method is used to calculate the power flow distribution of the distribution network, and a safety margin index is defined to evaluate the carrying capacity of the lines, thereby obtaining a set of transferable lines that meet the line safety margin.

[0010] Step 3: Taking into account the principles of prioritizing high voltage levels, important users, and loss load, construct a distribution network load transfer model. Combined with a set of transferable lines that meet the safety margin, use a parallel tabu search algorithm to find the optimal transfer path in the safety solution space to obtain the optimal line transfer scheme.

[0011] Step 4: Based on the power flow distribution results of the distribution network after the transfer, calculate the line fault probability and mark the lines that are higher than the risk threshold to provide early warning information for operators.

[0012] Furthermore, in step 1, the distribution network coefficient includes the network topology, line impedance and rated capacity, location and status of sectionalizing switches and tie switches, distributed photovoltaic output includes the active power output and reactive power compensation power of distributed photovoltaics, energy storage equipment output includes the active power regulation power of energy storage equipment, load demand includes the active power demand and reactive power demand of each node, and fault location information includes the sectionalizing switch tripping signal related to the fault area.

[0013] Furthermore, in step 1, the output of distributed photovoltaic and energy storage devices is determined using the following strategy:

[0014] (1) Distributed photovoltaic power output

[0015] The operating level of distributed photovoltaic (PV) is set to not exceed the rated range, thus distributed PV can be regarded as a PQ constant-type distributed power source participating in power flow calculation;

[0016] (2) Active power output of energy storage equipment

[0017] The energy storage device is always connected to one node in the distribution network. When the active power demand of the load is unbalanced with the active power output of distributed photovoltaic power, the energy storage device is used to maintain the power balance of the system.

[0018] a. When the active power demand of the load exceeds the active power output of distributed photovoltaic power, the adjustment shall be carried out according to the priority of "energy storage equipment discharge → power purchase from the upstream grid via the interconnection line";

[0019] b. When the active power demand of the load is less than the active power output of the distributed photovoltaic system, the adjustment shall be carried out according to the priority of "charging energy storage equipment → sending out excess power through the interconnection line".

[0020] Furthermore, in step 2, the forward-backward substitution method is used to calculate the power flow distribution of the distribution network before the transfer after fault isolation, including the following steps:

[0021] a. Based on the imbalance between system load power demand and distributed photovoltaic output, the output of energy storage devices and interconnection lines is obtained;

[0022] b. Calculate the injected complex power at each node. ,Right now

[0023]

[0024] In the formula, and They are nodes The active and reactive power injected at the point; and They are divided into nodes. The active power output and reactive power compensation of distributed photovoltaic power; and They are nodes Active and reactive power transmitted to the tie line; and They are nodes Active power demand and reactive power demand of the load; For nodes The active power regulation capacity of the energy storage device;

[0025] c. Based on the injection power of each node Given the initial voltages of each node, calculate the injected current at the terminal node. ,Right now:

[0026]

[0027] In the formula, and They are nodes The injected current phasor and voltage phasor, This represents the number of iterations.

[0028] d. Based on the calculated end-node currents, substitute back to obtain the current flowing through each branch, i.e.:

[0029]

[0030] In the formula, For nodes Connected upper-level branches Current phasor; Number the branch roads; For nodes A set of lower-level branches that are directly connected;

[0031] e. From the current injected at the starting node and the current flowing through each segment of the line, the voltage at each node in the system can be calculated starting from the beginning, i.e.:

[0032]

[0033] In the formula, For nodes The voltage phasor of the directly connected previous node; For nodes This refers to the branch current at the end node; Number the branch roads; branch road impedance;

[0034] f. The criteria for judging tidal convergence are:

[0035]

[0036] In the formula, For the first The longitudinal component of the voltage at the next iteration; For the first The transverse component of the voltage during the next iteration; To ensure convergence accuracy, if the voltage imbalance component at any node exceeds the convergence criterion, repeat steps c~e until the convergence criterion is met.

[0037] g. Calculate the power flowing through the branch, i.e.:

[0038]

[0039] In the formula, For connecting nodes , The complex power flowing through the branch.

[0040] Furthermore, in step 2, assessing the line's carrying capacity includes the following steps:

[0041] a. Based on the line heat balance equation, the line The current carrying capacity can be expressed as:

[0042]

[0043] In the formula, For convection cooling, For radiative heat dissipation, To absorb heat from sunlight, For the line The carrying capacity, Indicates the temperature of the conductor. Resistance per unit length at that time;

[0044] b. Route The remaining capacity can be expressed as:

[0045]

[0046] In the formula, For the line Rated voltage, The circuit obtained by iterative calculation using the forward-backward substitution method The current amplitude;

[0047] c. Obtain a set of transferable lines that satisfy the safety margin constraints. :

[0048]

[0049] In the formula, For the line Safety margin, For margin threshold, The calculation method is as follows:

[0050]

[0051] In the formula, For the line Rated capacity.

[0052] Furthermore, in step 3, the distribution network load transfer model is as follows:

[0053] (1) Objective function

[0054] In the process of load transfer in the distribution network, taking into account voltage level, important users, and load loss, the following weighted objective function is constructed to minimize it:

[0055]

[0056] in, , as well as Let represent the objective functions for prioritizing high voltage levels, prioritizing important users, and prioritizing load loss, respectively. , as well as These are the corresponding weight coefficients. The specific representations of the three sub-objective functions are as follows:

[0057] a. High voltage level preferred

[0058] Since high-voltage lines experience lower losses when transmitting the same power, prioritizing high-voltage lines as load transfer paths can approximate minimizing the active power loss of the distribution network.

[0059]

[0060] in, This indicates the total number of branches in the distribution network; branch road The switch has 0-1 state variables, where 0 and 1 represent the open and closed states of the switch, respectively. and They are the branch roads that flow through. Active power and reactive power; and Representing branch roads Resistance and nodes The square of the voltage amplitude;

[0061] b. Prioritize important users

[0062] Prioritize restoring power to critical users:

[0063]

[0064] in, For nodes The importance weight of the user received at the location; when When this happens, it means the switch is off, and the branch circuit... Downstream nodes The load has not been restored to power.

[0065] c. Prioritize loss load

[0066] Minimize the load that cannot be recovered due to insufficient capacity of the transfer path:

[0067]

[0068] in, Represents a node Active load at the location; when When, it means the switch is closed, and the branch circuit... Downstream nodes Power was restored to the affected load.

[0069] (2) Constraints

[0070] The following constraints must be met for the operation of the power distribution network:

[0071] Current balance constraint

[0072]

[0073]

[0074]

[0075]

[0076] In the formula, and They represent time periods respectively. node Injected active and reactive power; Based on nodes It is the set of branch end nodes of the first node; Based on nodes The set of the starting nodes of the branches of the terminal nodes; For time period branch road The square of the current amplitude; and Representing branch roads Resistance and reactance; Indicates time period node The square of the voltage amplitude;

[0077] Network topology constraints

[0078] For a distribution network to operate normally, it must meet the condition of radial operation, meaning that there are no ring networks in the network;

[0079] Branch current constraint

[0080] The current flowing through each branch in a distribution network must not exceed the maximum allowable current for that line, that is:

[0081]

[0082] in, branch road The maximum value of the square of the allowable current amplitude;

[0083] Node voltage constraints

[0084] The voltage at each load node in the distribution network must be within the rated range:

[0085]

[0086] in, and Representing nodes respectively The maximum and minimum values ​​of the square of the allowable voltage amplitude.

[0087] Furthermore, in step 3, the implementation of the parallel tabu search algorithm includes the following:

[0088] (1) Optimize variable design

[0089] An N-dimensional coordinate system is used to encode switches in the distribution network. The dimension of the coordinate system corresponds to the number of interconnecting switches in the network, and each coordinate dimension corresponds to a loop. Points on the coordinate axes represent switches within those loops. When optimizing in the N-dimensional solution space, the coordinates of a point represent the switch number that needs to be turned on in each loop. Furthermore, the feasible solution space is the set of lines that meet the safety margin; for lines that do not meet the safety margin, their switches must be in the open state.

[0090] (2) Neighborhood structure design

[0091] Based on the constructed N-dimensional coordinate system, "+1" and "-1" operations are performed on the switch state variables in each dimension to move them, corresponding to the movement operations of switches in the network topology diagram, thus generating an initial neighborhood set. Candidate solutions are randomly selected from this set and searched in the N-dimensional coordinate system. The specific number of selected solutions can be determined according to the scale of the power distribution network and the requirements for the optimization performance of the algorithm.

[0092] (3) Taboo table design

[0093] The coordinates of the already searched neighborhood set are set as tabu objects, and the tabu length is the term of the tabu object in the tabu table. Only when its value is 0 is the tabu object unbanned and released.

[0094] (4) Design of the contempt criterion and termination criterion

[0095] Disregard rule: If all candidate solutions are taboo, and there is a candidate solution among the taboo objects that is better than the current best solution, then its taboo attribute will be ignored, and the candidate solution will be directly used as the current solution and the current best solution.

[0096] End-of-search criterion: The maximum number of iterations that allow the optimal state to remain unchanged. The algorithm terminates when the number of iterations to reach the optimal state reaches a certain limit.

[0097] Furthermore, in step 4, the probability of line faults after power transfer is calculated using the following steps:

[0098] a. Since the line failure rate is strongly correlated with the load rate, a "load rate - failure rate" model is used to calculate the line failure probability after power transfer. The load factor is expressed by the following formula:

[0099]

[0100] In the formula, For time period After transfer line Apparent power;

[0101] b. Therefore, calculate the transmission line after the transfer. Failure rate :

[0102]

[0103] In the formula, For the line The baseline failure rate is obtained from historical data statistics; This is the load sensitivity factor, which is related to the line type;

[0104] c. Based on the set high-risk threshold For satisfying The route They are marked as high-risk lines to provide early warning information to operators.

[0105] This application also provides a distribution network partial load segmentation and transfer device, including a memory and a processor. The memory stores a computer program, and when the computer program is called and executed by the processor, it implements the distribution network partial load segmentation and transfer method as described above.

[0106] This application also provides a computer-readable medium storing a computer program, which, when executed by a computer, implements the method for partial load transfer in a distribution network as described above.

[0107] In summary, the beneficial effects of this application are:

[0108] This invention can calculate the power flow distribution of the distribution network before transfer after a fault occurs, based on the distribution network coefficient, output of distributed photovoltaic and energy storage equipment, load demand, and fault location information. It also defines a safety margin index and selects a set of transferable safe lines. A distribution network load transfer model integrating high-voltage priority, important user priority, and loss load priority is constructed. Based on the set of transferable safe lines, a parallel tabu search algorithm is used to find the optimal transfer scheme in the safe solution space. The fault rate is calculated based on the line load rate after transfer, and high-risk lines exceeding the threshold are marked. This enables effective assessment of the safe operation status of lines and provides a load transfer scheme that considers multi-objective collaborative optimization in real time. Attached Figure Description

[0109] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0110] Figure 1This is a flowchart of a method for partial load transfer in a distribution network based on line carrying capacity assessment and parallel tabu search algorithm, according to an embodiment of the present invention.

[0111] Figure 2 This is a flowchart of the forward-backward substitution method according to an embodiment of the present invention;

[0112] Figure 3 This is a flowchart of the parallel tabu search algorithm according to an embodiment of the present invention. Detailed Implementation

[0113] The specific embodiments of this application are described in detail below with reference to the accompanying drawings.

[0114] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0115] This embodiment provides a method for local load segmentation transfer in a distribution network based on line carrying capacity assessment and a parallel tabu search algorithm. Figure 1 This is a flowchart of a method for partial load transfer in a distribution network based on line carrying capacity assessment and parallel tabu search algorithm, according to an embodiment of the present invention. Figure 1 As shown, the method includes the following steps:

[0116] Step S101: Obtain information on the distribution network coefficient, output of distributed photovoltaic and energy storage equipment, load demand, and fault location;

[0117] Step S102: For the distribution network topology after disconnecting the relevant disconnecting switches in the fault area, the forward-backward substitution method is used to calculate the power flow distribution of the distribution network, and a safety margin index is defined to evaluate the carrying capacity of the lines, thereby obtaining a set of transferable lines that meet the line safety margin.

[0118] Step S103: Taking into account the principles of prioritizing high voltage levels, important users, and loss load, a distribution network load transfer model is constructed. Combined with a set of transferable lines that meet the safety margin, a parallel tabu search algorithm is used to find the optimal transfer path in the safety solution space to obtain the optimal line transfer scheme.

[0119] Step S104: Based on the power flow distribution results of the distribution network after the transfer, calculate the line fault probability and mark the lines that are higher than the risk threshold to provide early warning information for operators.

[0120] In summary, this invention can obtain information on distribution network coefficients, output of distributed photovoltaic and energy storage devices, load demand, and fault location; it uses the forward-backward substitution method to calculate the power flow distribution of the distribution network before transfer after a fault occurs, defines a safety margin index, and selects a set of transferable safe lines; it constructs a distribution network load transfer model that integrates high-voltage priority, important user priority, and loss load priority, and uses a parallel tabu search algorithm to find the optimal transfer scheme in the safe solution space based on the set of transferable safe lines; it calculates the fault rate based on the line load rate after transfer, marks high-risk lines exceeding the threshold, and can effectively assess the safe operation status of lines, providing load transfer schemes that consider multi-objective collaborative optimization in real time.

[0121] In some embodiments, in step S101, the output of the distributed photovoltaic and energy storage devices is determined using the following strategy:

[0122] (1) Distributed photovoltaic power output

[0123] The operating level of distributed photovoltaic (PV) is set to not exceed the rated range, thus distributed PV can be regarded as a PQ constant-type distributed power source participating in power flow calculation;

[0124] (2) Active power output of energy storage equipment

[0125] The energy storage device is always connected to one node in the distribution network. When the active power demand of the load is unbalanced with the active power output of distributed photovoltaic power, the energy storage device is used to maintain the power balance of the system.

[0126] a. When the active power demand of the load exceeds the active power output of distributed photovoltaic power, the adjustment shall be carried out according to the priority of "energy storage equipment discharge → power purchase from the upstream grid via the interconnection line";

[0127] b. When the active power demand of the load is less than the active power output of the distributed photovoltaic system, the adjustment shall be carried out according to the priority of "charging energy storage equipment → sending out excess power through the interconnection line".

[0128] In some embodiments, in step S102, Figure 2 This is a flowchart of the forward-backward substitution method according to an embodiment of the present invention, as follows: Figure 2 As shown, the forward-backward substitution method is used to calculate the power flow distribution of the distribution network before transfer after fault isolation, including the following steps:

[0129] Step S201: Determine the output of the energy storage equipment and interconnection lines.

[0130] Step S202: Calculate the injected complex power at each node. That is:

[0131]

[0132] In the formula, and They are nodes The active and reactive power injected at the point; and They are divided into nodes. The active power output and reactive power compensation of distributed photovoltaic power; and They are nodes Active and reactive power transmitted to the tie line; and They are nodes Active power demand and reactive power demand of the load; For nodes The active power regulation capacity of the energy storage device.

[0133] Step S203: Calculate the injected current at the end node. The calculation method is as follows:

[0134] Based on the injection power of each node Given the initial voltages of each node, calculate the injected current at the terminal node. ,Right now:

[0135]

[0136] In the formula, and They are nodes The injected current phasor and voltage phasor, This represents the number of iterations.

[0137] Step S204: Substitute the current of each branch back. The calculation method is as follows:

[0138] Based on the calculated end-node currents, the currents flowing through each branch are obtained by substituting back into the calculated end-node currents, i.e.:

[0139]

[0140] In the formula, For nodes Connected upper-level branches Current phasor; Number the branch roads; For nodes A set of lower-level branches that are directly connected.

[0141] Step S205: Advance the voltage of each node. The calculation method is as follows:

[0142] The voltage at each node in the system can be calculated from the current injected at the starting node and the current flowing through each segment of the line, starting from the beginning:

[0143]

[0144] In the formula, For nodes The voltage phasor of the directly connected previous node; For nodes This refers to the branch current at the end node; Number the branch roads; branch road The impedance.

[0145] Step S206: Power flow convergence assessment. The assessment method is as follows:

[0146] The criteria for judging the convergence of currents are:

[0147]

[0148] In the formula, For the first The longitudinal component of the voltage at the next iteration; For the first The transverse component of the voltage during the next iteration; To ensure convergence accuracy, if the voltage imbalance component at any node exceeds the convergence criterion, repeat steps S203 to S205 until the convergence criterion is met.

[0149] Step S207: Calculate the power of each branch. The calculation method is as follows:

[0150] Calculate the power flowing through the branch, i.e.:

[0151]

[0152] In the formula, For connecting nodes , The complex power flowing through the branch.

[0153] In some instances, step S102, assessing the line's carrying capacity includes the following steps:

[0154] a. Based on the line heat balance equation, the line The current carrying capacity can be expressed as:

[0155]

[0156] In the formula, For convection cooling, For radiative heat dissipation, To absorb heat from sunlight, For the line The carrying capacity, Indicates the temperature of the conductor. Resistance per unit length at that time;

[0157] b. Route The remaining capacity can be expressed as:

[0158]

[0159] In the formula, For the line Rated voltage, The circuit obtained by iterative calculation using the forward-backward substitution method The current amplitude;

[0160] c. Obtain a set of transferable lines that satisfy the safety margin constraints. :

[0161]

[0162] In the formula, For the line Safety margin, For margin threshold, The calculation method is as follows:

[0163]

[0164] In the formula, For the line Rated capacity.

[0165] In some instances, in step S103, the distribution network load transfer model is as follows:

[0166] (1) Objective function

[0167] In the process of load transfer in the distribution network, taking into account voltage level, important users, and load loss, the following weighted objective function is constructed to minimize it:

[0168]

[0169] in, , as well as Let represent the objective functions for prioritizing high voltage levels, prioritizing important users, and prioritizing load loss, respectively. , as well as These are the corresponding weight coefficients. The specific representations of the three sub-objective functions are as follows:

[0170] a. High voltage level preferred

[0171] Since high-voltage lines experience lower losses when transmitting the same power, prioritizing high-voltage lines as load transfer paths can approximate minimizing the active power loss of the distribution network.

[0172]

[0173] in, This indicates the total number of branches in the distribution network; branch road The switch has 0-1 state variables, where 0 and 1 represent the open and closed states of the switch, respectively. and They are the branch roads that flow through. Active power and reactive power; and Representing branch roads Resistance and nodes The square of the voltage amplitude;

[0174] b. Prioritize important users

[0175] Prioritize restoring power to critical users:

[0176]

[0177] in, For nodes The importance weight of the user received at the location; when When this happens, it means the switch is off, and the branch circuit... Downstream nodes The load has not been restored to power.

[0178] c. Prioritize loss load

[0179] Minimize the load that cannot be recovered due to insufficient capacity of the transfer path:

[0180]

[0181] in, Represents a node Active load at the location; when When, it means the switch is closed, and the branch circuit... Downstream nodes Power was restored to the affected load.

[0182] (2) Constraints

[0183] The following constraints must be met for the operation of the power distribution network:

[0184] Current balance constraint

[0185]

[0186]

[0187]

[0188]

[0189] In the formula, and They represent time periods respectively. node Injected active and reactive power; Based on nodes It is the set of branch end nodes of the first node; Based on nodes The set of the starting nodes of the branches of the terminal nodes; For time period branch road The square of the current amplitude; and Representing branch roads Resistance and reactance; Indicates time period node The square of the voltage amplitude;

[0190] Network topology constraints

[0191] For a distribution network to operate normally, it must meet the condition of radial operation, meaning that there are no ring networks in the network;

[0192] Branch current constraint

[0193] The current flowing through each branch in a distribution network must not exceed the maximum allowable current for that line, that is:

[0194]

[0195] in, branch road The maximum value of the square of the allowable current amplitude;

[0196] Node voltage constraints

[0197] The voltage at each load node in the distribution network must be within the rated range:

[0198]

[0199] in, and Representing nodes respectively The maximum and minimum values ​​of the square of the allowable voltage amplitude.

[0200] In some embodiments, in step S103 Figure 3 This is a flowchart of the parallel tabu search algorithm according to an embodiment of the present invention, as follows: Figure 3 As shown, the implementation of the parallel tabu search algorithm includes the following:

[0201] (1) Optimize variable design

[0202] An N-dimensional coordinate system is used to encode switches in the distribution network. The dimension of the coordinate system corresponds to the number of interconnecting switches in the network, and each coordinate dimension corresponds to a loop. Points on the coordinate axes represent switches within those loops. When optimizing in the N-dimensional solution space, the coordinates of a point represent the switch number that needs to be turned on in each loop. Furthermore, the feasible solution space is the set of lines that meet the safety margin; for lines that do not meet the safety margin, their switches must be in the open state.

[0203] (2) Neighborhood structure design

[0204] Based on the constructed N-dimensional coordinate system, "+1" and "-1" operations are performed on the switch state variables in each dimension to move them, corresponding to the movement operations of switches in the network topology diagram, thus generating an initial neighborhood set. Candidate solutions are randomly selected from this set and searched in the N-dimensional coordinate system. The specific number of selected solutions can be determined according to the scale of the power distribution network and the requirements for the optimization performance of the algorithm.

[0205] (3) Taboo table design

[0206] The coordinates of the already searched neighborhood set are set as tabu objects, and the tabu length is the term of the tabu object in the tabu table. Only when its value is 0 is the tabu object unbanned and released.

[0207] (4) Design of the contempt criterion and termination criterion

[0208] Disregard rule: If all candidate solutions are taboo, and there is a candidate solution among the taboo objects that is better than the current best solution, then its taboo attribute will be ignored, and the candidate solution will be directly used as the current solution and the current best solution.

[0209] End-of-search criterion: The maximum number of iterations that allow the optimal state to remain unchanged. The algorithm terminates when the number of iterations to reach the optimal state reaches a certain limit.

[0210] In some instances, in step S104, the probability of line fault after power transfer is calculated using the following steps:

[0211] a. Since the line failure rate is strongly correlated with the load rate, a "load rate - failure rate" model is used to calculate the line failure probability after power transfer. The load factor is expressed by the following formula:

[0212]

[0213] In the formula, For time period After transfer line Apparent power;

[0214] b. Therefore, calculate the transmission line after the transfer. Failure rate :

[0215]

[0216] In the formula, For the line The baseline failure rate is obtained from historical data statistics; This is the load sensitivity factor, which is related to the line type;

[0217] c. Based on the set high-risk threshold For satisfying The route They are marked as high-risk lines to provide early warning information to operators.

[0218] Another specific embodiment of this application provides a distribution network partial load segmentation transfer device, including a memory and a processor. The memory stores a computer program, and when the computer program is called and executed by the processor, it implements the distribution network partial load segmentation transfer method as described above.

[0219] Another specific embodiment of this application provides a computer-readable medium storing a computer program, which, when executed by a computer, implements the method for partial load transfer in a distribution network as described above.

[0220] The above description is only a preferred embodiment of this application. It should be noted that for those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of this application, and these all fall within the protection scope of this application.

Claims

1. A method for local load sectionalizing and transfer in an electric distribution network, characterized by, The method comprises the following steps: Step 1, obtaining power distribution network network coefficient, distributed photovoltaic and energy storage device output, load demand and fault position information; Step 2, for the power distribution network topology after disconnecting the related disconnectors of the fault area, the forward-backward substitution method is used to calculate the power distribution of the power distribution network, and a safety margin index is defined to evaluate the carrying capacity of the line, so as to obtain a set of transferable lines that meet the safety margin of the line; Step 3, considering the principles of high voltage level priority, important user priority and loss load quantity priority, a power distribution network load transfer model is constructed, and combined with the set of transferable lines that meet the safety margin, a parallel tabu search algorithm is used to find the optimal transfer path in the safe solution space, and the optimal line transfer scheme is obtained; Step 4, based on the power flow distribution result of the power distribution network after transfer, the line fault probability is calculated, and the lines higher than the risk threshold are marked to provide reference for the warning information of the operation personnel.

2. The method of claim 1, wherein, In step 1, the power distribution network network coefficient includes network topology structure, line impedance and rated capacity, the position and state of sectional switch and tie switch, the distributed photovoltaic output includes active power output and reactive power compensation power of distributed photovoltaic, the energy storage device output includes active power regulation power of energy storage device, the load demand includes active power demand and reactive power demand of each node, and the fault position information includes sectional switch tripping signal related to the fault area.

3. The method of claim 1, wherein, In step 1, the output of distributed photovoltaic and energy storage device is determined by the following strategies: (1) Distributed photovoltaic output The running level of distributed photovoltaic is set to be not more than the rated range, so that the distributed photovoltaic is regarded as a PQ constant type distributed power source to participate in the power flow calculation; (2) Active power output of energy storage device The energy storage device is set to be connected with one node in the power distribution network, and when the active power demand of the load is not balanced with the active power output of the distributed photovoltaic, the energy storage device is used to maintain the system power balance: a. When the active power demand of the load is greater than the active power output of the distributed photovoltaic, the energy storage device is discharged according to the priority of "purchasing power from the upper-level power grid through the tie line"; b. When the active power demand of the load is less than the active power output of the distributed photovoltaic, the energy storage device is charged according to the priority of "sending excess power through the tie line".

4. The method of claim 1, wherein, In step 2, the forward-backward substitution method is used to calculate the power flow distribution of the power distribution network before transfer after fault isolation, comprising the following steps: a. According to the imbalance between the system load power demand and the distributed photovoltaic output, the output of the energy storage device and the tie line is obtained; b. Calculate the injected complex power of each node i.e. ； wherein, and are the active power and the reactive power injected at the nodes ; and are the active power and the reactive power of the distributed photovoltaic at the nodes ; and are the active power and the reactive power transmitted to the tie line at the nodes ; and are the active power and the reactive power demand of the load at the nodes ; is the active power of the energy storage device at the nodes ; c. Calculate the end node injection current based on the injection power of each node and the set initial voltage of each node i.e.: ； wherein and are the injected current and voltage phasors of the node respectively, is the iteration number; d. According to the calculated end node current, the current flowing through each branch is obtained, that is: ； In the formula, For nodes Connected upper-level branches Current phasor; Number the branch roads; For nodes A set of lower-level branches that are directly connected; e. From the start node injection current and the current flowing through each section of line, the voltage of each node in the system can be calculated from the start node, that is: ； wherein is the voltage phasor of the previous node directly connected to the node ; is the voltage phasor of the previous node directly connected to the node ; is the branch number; is the impedance of the branch ; f. The judgment basis for the convergence of power flow is: ； wherein is the longitudinal component of the voltage at the nth iteration; is the transverse component of the voltage at the nth iteration; is the longitudinal component of the voltage at the nth iteration; is the transverse component of the voltage at the nth iteration; is the convergence accuracy; if the unbalanced component of the voltage of any node is greater than the convergence criterion, steps c-e are repeated until the convergence criterion is met; g. The power flowing through the branch is calculated, that is: ； wherein is the complex power flowing through the branch of the connection node , .

5. The method of claim 1, wherein, In step 2, the carrying capacity of the line includes the following steps: a. Based on the line heat balance equation, the line carrying capacity can be expressed as: ； wherein is the convective heat loss, is the radiative heat loss, is the solar heat gain, is the line current capacity, represents the resistance per unit length of the conductor at a conductor temperature of . b. Line The remaining capacity can be expressed as: ； wherein is the rated voltage of the line is the current amplitude of the line is the current amplitude of the line calculated by the iterative forward-backward substitution method c. obtaining a set of transferable lines that satisfy a safety margin constraint : ； In the formula, is the safety margin of the line , is the margin threshold, The calculation method is: ； In the formula, is the rated capacity of the line .

6. The method of claim 1, wherein, In step 3, the power distribution network load transfer model is: (1) Objective function In the process of power distribution network load transfer, considering the voltage level, important user and loss load quantity, the following weighted objective function is constructed to minimize: ； wherein, , and respectively represent the objective functions corresponding to high voltage level priority, important user priority and loss load quantity priority, , and are the corresponding weight coefficients; wherein the specific representations of the three sub-objective functions are as follows: a. High voltage level priority Since the high-voltage line has lower loss when transmitting the same power, the high-voltage line is preferentially selected as the load transfer path, which can approximate to minimize the active power loss of the distribution network: ； wherein, denotes the total number of branches in the distribution network; is the switch 0-1 state variable of branch , respectively representing the open and closed state of the switch by 0 and 1; and are the active power and reactive power flowing through branch , respectively; and denote the resistance of branch and the voltage amplitude square of node , respectively. b. Priority for important users Prioritize the restoration of power supply to important users: ； wherein, is a node importance weight of the user at the node; when means that the switch is open, the branch downstream node the load at the node has not been restored c. Loss load priority Minimize the load that cannot be restored due to insufficient transfer path capacity: ； wherein, represents the active load at the node ; when , means that the switch is closed, the branch downstream node is powered back on; (2) Constraint conditions The following constraint conditions need to be met for the operation of the distribution network: Power flow balance constraint ， ， ， ； wherein and denote the time period node injected active and reactive power; is a set of branch end nodes with node as a head node; is a set of branch head nodes with node as an end node; is a time period branch current magnitude squared; and denote the resistance and reactance of branch ; denotes the time period node voltage magnitude squared; Network topology constraint The distribution network needs to meet the condition of radial operation in normal operation, that is, there is no loop in the network; Branch current constraint The current flowing through each branch in the distribution network cannot exceed the maximum current allowed by the line, that is: ； wherein is a branch allows the maximum value of the square of the amplitude of the current flowing through Node voltage constraint The voltage of each load node in the distribution network must be within the rated range: ； wherein, and denote the nodes allowing the maximum and minimum of the square of the amplitude of the voltage.

7. The method of claim 1, wherein, In step 3, the implementation of the parallel tabu search algorithm includes the following contents: (1) Optimization variable design The switches in the distribution network are coded using the coding strategy of the N-dimensional coordinate system; where the number of dimensions of the coordinate system corresponds to the number of tie switches in the network, and each dimension of the coordinate corresponds to a switch in the loop; when searching in the N-dimensional solution space, the coordinates of the point correspond to the switch numbers that need to be opened in each loop; in addition, the feasible solution space is a set of lines that meet the safety margin, and for lines that do not meet the safety margin, the switch must be in the off state; (2) Neighborhood structure design Based on the constructed N-dimensional coordinate system, "+1" and "-1" operations are performed in each dimension of the coordinate for switch state variables to move, which corresponds to the movement operation of the switch in the network topology graph, thereby generating an initial neighborhood set; the candidate solution is randomly selected from the neighborhood set, and the search is performed in the N-dimensional coordinate system; (3) Tabu table design The coordinates of the neighborhood set that have been searched are set as tabu objects, and the tabu length is the term corresponding to the tabu object in the tabu table. Only when the value is 0, the tabu object is released from the tabu; (4) Design of contempt criteria and termination criteria Contempt criteria: In the case where all candidate solutions are tabu, if there is a candidate solution better than the current optimal solution among the tabu objects, the tabu attribute of this candidate solution is ignored, and the candidate solution is directly used as the current solution and the current optimal solution. Termination criterion: maximum number of consecutive iterations for which the optimal state remains unchanged The algorithm terminates when the number of consecutive iterations for which the optimal state remains unchanged reaches a defined value.

8. The method of claim 1, wherein, In step 4, the line failure probability after transfer is calculated as follows: a. Since the line failure rate is strongly related to the load rate, the "load rate-failure rate" model is used to calculate the line failure probability after the transfer; the load rate of the line is expressed by the following equation: ； wherein is the time period post-transfer line apparent power; b. From this, the failure rate of the line after transfer is calculated :​ ； In the formula, is the basic failure rate of the line , which is obtained from historical data statistics; is the load sensitivity coefficient, which is related to the line type. c. Based on the set high-risk threshold For satisfying The route They are marked as high-risk lines to provide early warning information to operators.

9. A power distribution network local load sectionalizing device, characterized by, The computer readable medium stores a computer program, and the computer program is called and executed by the processor to implement the local load section transfer method of the distribution network according to any one of claims 1-8.

10. A computer readable medium characterized by The computer readable medium stores a computer program, and the computer program is called and executed by the processor to implement the local load section transfer method of the distribution network according to any one of claims 1-8.

Images