A switching control method and system for a capacitor

Abstract

The present application relates to the technical field of capacitor switching control, and particularly relates to a method and system for capacitor switching control. The method includes: obtaining the effective voltage value and reactive power of each node at each moment through the voltage and current data of each node in the power system at each moment and its adjacent moments; obtaining the nine-zone diagram in the power system; adding a local voltage upper limit and a local voltage lower limit to the nine-zone diagram to correct the nine-zone diagram into an eleven-zone diagram; obtaining the corrected local voltage upper limit and local voltage lower limit of each node within each update period; obtaining the updated eleven-zone diagram of each node within each update period; obtaining a plurality of capacitor capacity vectors; determining the fitness corresponding to each capacitor capacity vector; correcting the explosion radius and the number of explosion sparks of each firework in the fireworks algorithm; obtaining the current optimal capacitor capacity vector according to the corrected fireworks algorithm and the fitness, and performing switching control on the capacitor. Thereby, the accuracy of capacitor switching control is improved.

Description

Technical Field

[0001] The present application relates to the technical field of capacitor switching control, and specifically relates to a method and system for switching control of capacitors. Background Art

[0002] Due to the characteristics of variable inductive loads and high operating losses in low-voltage distribution networks, phenomena such as low power factor and reactive power imbalance frequently occur. The compensation equipment in low-voltage distribution networks generally operates in an environment with variable power factor and no human monitoring. Therefore, it is required that the compensation equipment in low-voltage distribution networks can automatically perform switching control according to the compensation demand. As a static var compensation device, an intelligent capacitor divides the switched capacitors into multiple groups and controls the switching according to the reactive power change of the power grid to achieve flexible adjustment of the reactive power compensation amount to ensure that the node voltage does not exceed the limit.

[0003] An intelligent capacitor is a discrete control device, and frequent switching will affect its lifespan. Reactive power compensation in a distribution network power system must consider the switching times of capacitors, and switching control needs to be performed separately on intelligent capacitors at different nodes. Different capacitor switching amounts in the distribution network result in voltage differences between nodes, causing line losses in the power system. Therefore, an intelligent capacitor needs to consider optimizing the control of multiple objectives such as node voltage, capacitor switching times, and line losses simultaneously. Due to the relatively random changes in the electrical state of the low-voltage distribution network power system, the existing capacitor switching control methods have poor optimization effects on multi-objective reactive power compensation. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present application is to provide a method and system for switching control of capacitors, and the specific technical solutions adopted are as follows:

[0005] In a first aspect, an embodiment of the present application provides a method for switching control of capacitors, and the method includes the following steps:

[0006] Obtain the effective voltage value and reactive power of each node at each moment through the voltage and current data of each node in the power system at each moment and its adjacent moments;

[0007] Obtain the nine-region diagram in the power system; add a preset local voltage upper limit and a local voltage lower limit to the nine-region diagram to correct the nine-region diagram into an eleven-region diagram; preset an update period, analyze the distribution of the effective voltage value and reactive power of each node at the starting moment in each update period in the eleven-region diagram, and the distribution of the effective voltage value and reactive power of each node in the adjacent update periods of each update period, to obtain the corrected local voltage upper limit and local voltage lower limit of each node in each update period; further obtain the updated eleven-region diagram of each node in each update period;

[0008] Combined with the current capacitor capacity invested in each node, as well as the distribution of the current effective voltage value and reactive power of each node in its updated eleven - zone diagram, randomly generate the capacitor capacity of each node; form the capacitor capacity vector from the capacitor capacities of all nodes in the power system; correspondingly, obtain multiple capacitor capacity vectors;

[0009] Analyze the active power loss of the power system, the switching times of all capacitors, and the distribution of the effective voltage values of each node under the control of each capacitor capacity vector for all nodes, and obtain the fitness corresponding to each capacitor capacity vector;

[0010] Utilize the distribution of the effective voltage value and reactive power of each node under the control of each capacitor capacity vector, as well as the distribution in its updated eleven - zone diagram, to correct the explosion radius and the number of explosion sparks of each firework in the fireworks algorithm; obtain the current optimal capacitor capacity vector according to the corrected fireworks algorithm and the fitness, and perform switching control on the capacitors.

[0011] In one embodiment, the determination of the corrected local voltage upper limit and local voltage lower limit includes:

[0012] For the starting moment of any update period, obtain the nodes whose reactive power is greater than the reactive power upper limit in the eleven - zone diagram, and whose effective voltage value is greater than the preset local voltage upper limit and less than the voltage upper limit in the eleven - zone diagram, and denote them as the first nodes;

[0013] For each first node, calculate the difference between the voltage upper limit in the eleven - zone diagram and the local voltage upper limit of the previous update period of the any update period, and denote it as the first difference. Calculate the difference between the reactive power at the starting moment of the any update period and the reactive power upper limit in the eleven - zone diagram, and denote it as the second difference;

[0014] Combined with the first difference and the second difference, obtain the upward adjustment amount of the local voltage upper limit of each first node in the any update period;

[0015] For each first node, calculate the difference between the local voltage upper limit and the local voltage lower limit of the previous update period of the any update period, and denote it as the third difference. Calculate the degree of dispersion of the effective voltage values at all moments in the previous update period of the any update period, and calculate the proportion of the time when the effective voltage value is less than the local voltage upper limit in the previous update period of the any update period to the entire update period;

[0016] Combined with the third difference, the degree of dispersion and the proportion, obtain the downward adjustment amount of the local voltage upper limit of each first node in the any update period;

[0017] The upper limit of the local voltage corrected by each first node in any update period is positively correlated with the upward adjustment amount of the local voltage upper limit, and is negatively correlated with the downward adjustment amount of the local voltage upper limit, and is also positively correlated with the upper limit of the local voltage in the previous update period of any update period;

[0018] For each node other than the first node in any update period, the upper limit of the local voltage corrected by it remains the same as the upper limit of the local voltage in the previous update period of any update period;

[0019] Based on the same analysis method as the upper limit of the local voltage corrected by each node in any update period, the lower limit of the local voltage corrected by each node in any update period is obtained.

[0020] In one embodiment, the determination of the lower limit of the local voltage corrected by each node in any update period includes:

[0021] At the starting moment of any update period, nodes with reactive power less than the lower limit of reactive power in the eleven-region diagram, and the effective voltage value less than the preset lower limit of local voltage and greater than the lower limit of voltage in the eleven-region diagram are obtained, and are denoted as second nodes;

[0022] For each second node, the third difference and the degree of dispersion are calculated, and the proportion of the time during which the effective voltage value is greater than the lower limit of the local voltage in the previous update period of any update period in the entire update period is calculated;

[0023] Combining the third difference, the degree of dispersion, and the proportion of each second node, the upward adjustment amount of the lower limit of the local voltage of each second node in any update period is obtained;

[0024] For each second node, the difference between the lower limit of the local voltage in the previous update period of any update period and the lower limit of voltage in the eleven-region diagram is calculated, and is denoted as the fourth difference, and the difference between the lower limit of reactive power in the eleven-region diagram and the reactive power at the starting moment of any update period is calculated, and is denoted as the fifth difference;

[0025] Combining the fourth difference and the fifth difference, the downward adjustment amount of the lower limit of the local voltage of each second node in any update period is obtained;

[0026] The lower limit of the local voltage corrected by each second node in any update period is positively correlated with the upward adjustment amount of the lower limit of the local voltage, and is negatively correlated with the downward adjustment amount of the lower limit of the local voltage, and is also positively correlated with the lower limit of the local voltage in the previous update period of any update period.

[0027] In one embodiment, the determination of the capacitor capacity of each node includes:

[0028] For each first node and each second node at the current moment, and for nodes whose reactive power at the current moment is greater than the lower limit of reactive power in the eleven - area diagram, less than the upper limit of reactive power in the eleven - area diagram, and whose effective voltage value is greater than the lower limit of voltage in the eleven - area diagram and less than the upper limit of voltage in the eleven - area diagram, set their capacitor capacity to be equal to the capacitor capacity put into operation at the current moment;

[0029] For the remaining nodes at the current moment, denoted as the third nodes, calculate the ideal capacitor capacity of each third node, obtain the interval formed by the capacitor capacity put into operation at the current moment of each third node and its ideal capacitor capacity, and select a random number within the interval as the capacitor capacity of each third node.

[0030] In one of the embodiments, the obtaining of the fitness corresponding to each capacitor capacity vector includes:

[0031] Calculate the cumulative sum of the differences between the effective voltage values of all nodes and the nominal voltage under the control of each capacitor capacity vector; calculate the sum of the switching times of all capacitors under the control of each capacitor capacity vector;

[0032] The fitness corresponding to each capacitor capacity vector is the fusion result of the cumulative sum, the sum of the switching times, and the active power loss of the power system under preset weights.

[0033] In one of the embodiments, the determination of the explosion radius includes:

[0034] Form the first coordinate with the reactive power and the effective voltage value of each node under the control of each capacitor capacity vector, and form the second coordinate with the mean value of the upper limit and the lower limit of reactive power in the eleven - area diagram, and the mean value of the upper limit and the lower limit of voltage;

[0035] Based on the distribution of the reactive power and the effective voltage value of each node under the control of each capacitor capacity vector in the eleven - area diagram, and the distance between the first coordinate of each node and the second coordinate, determine the first adjustment factor of the explosion radius;

[0036] The calculation method of the explosion radius is: ; where is the explosion radius of the k - th firework, is the first adjustment factor of the explosion radius of the k - th firework, is the fitness corresponding to the capacitor capacity vector represented by the k - th firework, is the fitness corresponding to the capacitor capacity vector represented by the i - th firework, is the minimum value of the fitness corresponding to all fireworks in the firework population, is a preset value greater than 0, is the number of fireworks in the firework population.

[0037] In one embodiment, the calculation method of the first adjustment factor of the explosion radius is as follows:

[0038] ; where L is the number of the third nodes controlled by the capacitor capacity vector represented by the k-th firework, is the number of nodes in the third nodes where the reactive power is less than the lower limit of the reactive power in the eleven-region diagram, and the effective voltage value is greater than the lower limit of the local voltage and less than the upper limit of the voltage in the eleven-region diagram, is the number of nodes in the third nodes where the reactive power is greater than the upper limit of the reactive power in the eleven-region diagram, and the effective voltage value is greater than the lower limit of the voltage in the eleven-region diagram and less than the upper limit of the local voltage, , and respectively represent the metric distances between the first and second coordinates of its g-th, f-th, and r-th nodes, , are respectively the differences between the effective voltage values of the f-th and r-th nodes and the lower limit of the local voltage.

[0039] In one embodiment, the determination of the number of explosion sparks includes:

[0040] Adopt the same analysis method as the first adjustment factor of the explosion radius to obtain the second adjustment factor of the number of explosion sparks;

[0041] The calculation method of the number of explosion sparks is as follows: ; where is the number of explosion sparks of the k-th firework, round[] is the rounding function, is the second adjustment factor of the number of explosion sparks of the k-th firework, is the maximum value of the fitness corresponding to all fireworks in the firework population.

[0042] In one embodiment, the calculation method of the second adjustment factor of the number of explosion sparks is as follows: .

[0043] In a second aspect, the embodiment of the present application further provides a switching control system for capacitors, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, the steps of the method described in any one of the above are implemented.

[0044] The present application has at least the following beneficial effects:

[0045] This application obtains the effective voltage values and reactive powers of each node at each moment through the voltage and current data of each node in the power system at each moment and its adjacent moments; obtains the nine-zone diagram in the power system; adds a preset local voltage upper limit and a local voltage lower limit to the nine-zone diagram, and corrects the nine-zone diagram to an eleven-zone diagram to reduce the phenomenon of "switching oscillation" of capacitors; presets an update period, analyzes the distribution of the effective voltage values and reactive powers of each node at the starting moment in each update period in the eleven-zone diagram, and the distribution of the effective voltage values and reactive powers of each node in the adjacent update periods of each update period, to obtain the corrected local voltage upper limit and local voltage lower limit of each node in each update period; avoids the drawback that the fixed local voltage upper limit and local voltage lower limit in the eleven-zone diagram have insufficient improvement effect on the "switching oscillation" phenomenon of capacitors, reduces the occurrence probability of the "switching oscillation" phenomenon of capacitors, and further obtains the updated eleven-zone diagram of each node in each update period; combines the currently installed capacitor capacity of each node, and the distribution of the current effective voltage value and reactive power of each node in its updated eleven-zone diagram, and randomly generates the capacitor capacity of each node; forms the capacitor capacity vectors of all nodes in the power system; correspondingly, obtains multiple capacitor capacity vectors, and uses them as the optimization variables of the fireworks algorithm; analyzes the active power loss of the power system, the switching times of all capacitors, and the distribution of the effective voltage values of each node under the control of each capacitor capacity vector for all nodes, to obtain the fitness corresponding to each capacitor capacity vector; the fitness is used as the optimization target of the subsequent fireworks algorithm, and by considering multiple factors, the accuracy of the finally optimized capacitor capacity is improved, and the reactive power compensation effect in the power system is improved; uses the distribution of the effective voltage values and reactive powers of each node under the control of each capacitor capacity vector, and the distribution in its updated eleven-zone diagram, to correct the explosion radius and the number of explosion sparks of each firework in the fireworks algorithm; improves the suitability of the explosion radius and the number of explosion sparks of each firework, and finally improves the optimization effect of the fireworks algorithm; obtains the currently optimal capacitor capacity vector according to the corrected fireworks algorithm and the fitness, and performs switching control on the capacitors, avoids the occurrence of the "switching oscillation" phenomenon caused by frequent switching of capacitors, prolongs the service life of the capacitors, and improves the reactive power compensation effect of the capacitors. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following described drawings are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0047] Figure 1The flowchart of the steps of a switching control method for a capacitor provided by an embodiment of the present application;

[0048] Figure 2 It is a schematic diagram of the eleven-region map;

[0049] Figure 3 It is the flowchart for obtaining the optimal capacitor capacity vector. Detailed implementation manners

[0050] In order to further elaborate on the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following combines the accompanying drawings and preferred embodiments to detail the specific implementation manners, structures, features and their effects of a switching control method and system for a capacitor proposed according to the present application. In the following description, different "an embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures or characteristics in one or more embodiments can be combined in any suitable form.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present application belongs.

[0052] The following specifically describes the specific solutions of a switching control method and system for a capacitor provided by the present application with reference to the accompanying drawings.

[0053] Please refer to Figure 1 , which shows the flowchart of the steps of a switching control method for a capacitor provided by an embodiment of the present application. The method includes the following steps:

[0054] S1. Obtain the effective voltage value and reactive power of each node at each moment through the voltage and current data of each node in the power system at each moment and its adjacent moments.

[0055] In this embodiment, intelligent capacitors are used to collect the voltage data and current data of each node in the power system. The collection frequencies of the voltage data and current data are both 1024 Hz. The voltage data at each moment and the previous 1023 adjacent voltage data are combined in time sequence to form the voltage sequence at each moment, that is, each voltage sequence at each moment contains 1024 voltage data, and the duration of each voltage sequence at each moment is 1 s. Using the same acquisition method for the voltage sequence at each moment, for the current data, the current sequence at each moment is obtained, and the capacitor capacity currently input to each node is obtained at each moment.

[0056] It should be noted that the implementer can set the acquisition frequencies of voltage data and current data according to the actual situation, which is not restricted in this embodiment. This embodiment adopts a co-compensation type intelligent capacitor and uses a magnetic latching relay as the switching switch to monitor the electrical state of the node at each moment and perform capacitor bank switching operations when abnormalities occur at the node.

[0057] Taking the voltage sequences and current sequences of each node at each moment as inputs, the FFT (Fast Fourier Transformation) algorithm is used to calculate and obtain the effective voltage values, reactive powers, and active powers of each node at each moment. The FFT algorithm and the calculations of the effective voltage values, reactive powers, and active powers of each node are well-known prior arts, and the specific processes will not be elaborated here.

[0058] S2. Obtain the nine-region diagram in the power system; add a preset local voltage upper limit and a local voltage lower limit to the nine-region diagram to correct it into an eleven-region diagram; preset an update period, analyze the distributions of the effective voltage values and reactive powers of each node at the starting moment in each update period in the eleven-region diagram, as well as the distributions of the effective voltage values and reactive powers of each node in the adjacent update periods of each update period, to obtain the corrected local voltage upper limit and local voltage lower limit of each node in each update period; further obtain the updated eleven-region diagram of each node in each update period.

[0059] Taking the duration of N consecutive voltage sequences as the period for adjusting the capacitor switching control strategy, and denoting it as an update period of the intelligent capacitor. In this embodiment, N is taken as 30, and the implementer can set it according to the actual situation, which is not restricted in this embodiment. Thus, N effective voltage values, N reactive powers, and N active powers of each node in the update period are obtained.

[0060] In the power system, the nine-region diagram divides the operating states of nodes into nine regions according to the effective voltage values and reactive powers of the nodes, and then, according to the situations of each region, different control methods are adopted to perform switching operations on the capacitor bank, so as to stabilize the grid voltage and reactive power within the normal range. The nine-region diagram method is a well-known prior art, and the specific process will not be elaborated here.

[0061] The eleven-region diagram adds a local voltage upper limit and a local voltage lower limit on the basis of the nine-region diagram to reduce "switching oscillation". However, the electrical states of the nodes in the low-voltage distribution network change randomly, and the fixed local voltage upper limit and local voltage lower limit in the eleven-region diagram have limited effects on reducing the "switching oscillation" of the intelligent capacitor. Therefore, in this embodiment, the eleven-region diagrams of different nodes in the power system are adjusted in real time through the effective voltage values and reactive powers within the update period of each node to further reduce the probability of "switching oscillation". Among them, the schematic diagram of the eleven-region diagram is as Figure 2 shown Figure 2Where Umax is the upper voltage limit, Umin is the lower voltage limit, Qmin is the lower reactive power limit, Qmax is the upper reactive power limit, U L is the local lower voltage limit, U H is the local upper voltage limit. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 respectively represent 11 regions. The control strategy of the capacitor corresponding to the eleven-region diagram is shown in Table 1.

[0062] Table 1 Control Strategy of Capacitor Corresponding to Eleven-Region Diagram

[0063]

[0064] In this embodiment, for different nodes, the upper voltage limit Umax, the lower voltage limit Umin, the upper reactive power limit Qmax, the lower reactive power limit Qmin, the local upper voltage limit U H , and the local lower voltage limit U L in the eleven-region diagram are obtained through the following specific process:

[0065] First, according to the regulation of GB12325-2008 Power Quality - Supply Voltage Deviation: for three-phase power supply with voltage of 20 kV and below, the voltage deviation is ±7% of the nominal voltage. Thus, the upper and lower voltage limits of the eleven-region diagram are set. In this embodiment, the nominal voltage is 220 V, the upper voltage limit Umax = 235 V (+7%), the lower voltage limit Umin = 205 V (-7%), the initial local upper voltage limit U H = 231 V (+5%), the initial local lower voltage limit U L = 209 V (-5%). The implementer can set the initial local upper voltage limit and the initial local lower voltage limit by himself / herself.

[0066] Second, in this embodiment, the automatic selection method is used to set the upper reactive power limit Qmax and the lower reactive power limit Qmin of the eleven-region diagram. The method of setting the upper and lower reactive power limits by the automatic selection method is a well-known existing technology and will not be elaborated here.

[0067] Finally, considering the change of inductive load of each node in the low-voltage distribution network power system at different operation stages, when the node is at the boundary of area 6 and area 8 and the boundary of area 4 and area 7, the intelligent capacitor is prone to the "switching oscillation" phenomenon. Therefore, for the nodes whose effective voltage value and reactive power are in area 6 and area 7 at the starting moment of each update cycle, the local upper voltage limit and the local lower voltage limit of their eleven-region diagrams are adjusted. The specific calculation method is as follows:

[0068] For the nodes whose voltage effective value and reactive power are in zone 6 at the start of the t-th update cycle, the longer the time that the voltage effective value is less than the local voltage upper limit in the t-1-th update cycle, the more violent the fluctuation of the node voltage effective value, reflecting that the change of the inductive load of the node is more drastic. In order to avoid "switching oscillation", the local voltage upper limit is lowered to stabilize it in zone 6, reducing the switching operation of the smart capacitor.

[0069] In addition, to prevent the reactive power of the node in zone 6 from being too large, when its reactive power is large, the local voltage upper limit is increased so that it can enter zone 8 for capacitor bank operation and restore the reactive power to the normal range. The node whose voltage effective value and reactive power are in zone 6 at the start of the tth update cycle is recorded as the first node, that is, the node whose reactive power is greater than the reactive power upper limit in the eleven-zone diagram, and whose voltage effective value is greater than the preset local voltage upper limit and less than the voltage upper limit in the eleven-zone diagram.

[0070] According to the reactive power and voltage effective value of the first node, the local voltage upper limit of the first node is calculated. The specific calculation method is:

[0071] ; In the formula, is the upper limit of the local voltage of each first node in the tth update cycle, is the local voltage upper limit of each first node in the t-1th update cycle, is the local voltage upper limit rise adjustment amount of each first node in the tth update cycle, is the local voltage upper limit decrease adjustment amount of each first node in the tth update period.

[0072] The specific calculation method of the local voltage upper limit increase adjustment amount and the local voltage upper limit decrease adjustment amount is:

[0073]

[0074]

[0075] In the formula, Indicates the upper voltage limit in the eleven-zone diagram; represents the local voltage lower limit of each first node in the t-1th update cycle; Indicates the discreteness of all voltage effective values ​​of each first node in the t-1th update cycle, reflecting the fluctuation of node voltage; Indicates that the effective value of the voltage of each first node in the t-1th update cycle is less than The proportion of the maintenance time to the entire update cycle; represents the difference between the reactive power at the start time of each first node in the tth update cycle and the upper limit of the reactive power in the eleven-zone diagram; norm() is the normalization function. Recorded as the first difference, Recorded as the second difference, Recorded as the third difference.

[0076] It should be noted that all the discrete degrees in this embodiment are calculated by standard deviation, and the implementer may choose other existing methods for calculation, such as variance, coefficient of variation, etc.

[0077] For the nodes whose voltage effective value and reactive power are in zone 7 at the start of the t-th update cycle, the longer the time that the voltage effective value is greater than the local voltage lower limit in the t-1-th update cycle, the more violent the fluctuation of the node voltage effective value, reflecting that the change of the inductive load of the node is more drastic. In order to avoid "switching oscillation", the local voltage lower limit is increased to stabilize it in zone 7, reducing the switching operation of the smart capacitor.

[0078] In addition, to prevent the reactive power of the node in zone 7 from being too small, when its reactive power is small, the local voltage lower limit is lowered so that it can enter zone 4 for capacitor bank removal operation to restore the reactive power to the normal range. The node whose voltage effective value and reactive power are in zone 7 at the start of the tth update cycle is recorded as the second node, that is, the node whose reactive power is less than the reactive power lower limit in the eleven-zone diagram, and whose voltage effective value is less than the preset local voltage lower limit, and greater than the voltage lower limit in the eleven-zone diagram.

[0079] According to the reactive power and voltage effective value of the second node, the local voltage lower limit of the second node is calculated. The specific calculation method is:

[0080] ; In the formula, is the lower limit of the local voltage of each second node in the tth update cycle, is the lower limit of the local voltage of each second node in the t-1th update cycle, is the local voltage lower limit rise adjustment amount of each second node in the tth update cycle, is the lower limit decrease adjustment amount of the local voltage of each second node in the tth update period.

[0081] The specific calculation method of the local voltage lower limit increase adjustment amount and the local voltage lower limit decrease adjustment amount is:

[0082]

[0083]

[0084] In the formula, Indicates the lower voltage limit in the eleven-zone diagram; Indicates the discreteness of all voltage effective values ​​of each second node in the t-1th update cycle, reflecting the fluctuation of node voltage; Indicates that the effective voltage value of each second node in the (t - 1)-th update cycle is greater than The proportion of the maintenance time in the entire update cycle; Indicates the difference between the lower limit of reactive power in the eleven-region diagram and the reactive power at the starting moment of each second node in the t-th update cycle; norm() is a normalization function. Denote As the fourth difference, Denote as the fifth difference.

[0085] For the remaining nodes except the first node in the t-th update cycle, their local voltage upper limits remain the same as those in the (t - 1)-th update cycle. For the remaining nodes except the second node in the t-th update cycle, their local voltage lower limits remain the same as those in the (t - 1)-th update cycle. Take the local voltage upper limit and local voltage lower limit obtained by each node in the t-th update cycle as the corrected local voltage upper limit and local voltage lower limit of each node in the t-th update cycle, and then obtain the updated eleven-region diagram of each node in the t-th update cycle.

[0086] S3. Combine the currently installed capacitor capacity of each node, and the distribution of the current effective voltage value and reactive power of each node in its updated eleven-region diagram, and randomly generate the capacitor capacity of each node; form the capacitor capacity vector from the capacitor capacities of all nodes in the power system; correspondingly, obtain multiple capacitor capacity vectors.

[0087] In this embodiment, the ideal capacitor capacity for the intelligent capacitor input at each node is determined by the power factor. According to the reactive power, active power, and ideal power factor of each node in the power system, calculate and obtain the ideal capacitor capacity to be input at each node. To ensure maximizing the power factor, the value range of the ideal power factor is set to 0.95 - 0.99. Among them, the ideal power factor in this embodiment takes the value of 0.99. The method for calculating the ideal capacitor capacity according to the reactive power, active power, and ideal power factor of each node at each moment is a well-known technology and will not be elaborated here.

[0088] Considering the characteristics of variable inductive loads in the low-voltage distribution network, when the active power and reactive power at the node fluctuate greatly, controlling the reactive power compensation of the intelligent capacitor with the ideal capacitor capacity is likely to cause the capacitor to act repeatedly and reduce the service life of the capacitor. Therefore, construct the capacitor capacity interval of each node as the optimization range for the subsequent switching control of its capacitor bank, specifically:

[0089] When the ideal capacitor capacity is greater than the capacitor capacity of the current intelligent capacitor input to the node, use the capacitor capacity of the current intelligent capacitor input to the node as the left endpoint of the interval, and use the ideal capacitor capacity of the node as the right endpoint of the interval to construct a closed interval as the capacitor capacity interval of this node;

[0090] When the capacity of the ideal capacitor is less than the capacity of the capacitor invested by the current intelligent capacitor into the node, use the capacity of the capacitor invested by the current intelligent capacitor into the node as the right endpoint of the interval and the capacity of the ideal capacitor of the node as the left endpoint of the interval to construct a closed interval as the capacitor capacity interval of the node.

[0091] When the capacity of the ideal capacitor is equal to the capacity of the capacitor invested by the current intelligent capacitor into the node, the capacitor capacity interval degenerates into a point, indicating that the capacity of the capacitor invested at this node is already in an ideal state and no operation is required.

[0092] In this embodiment, according to the positions of different nodes in their respective eleven-region diagrams at the current moment in the low-voltage distribution network power system, a capacitor capacity vector of the power system is constructed, specifically as follows:

[0093] For the nodes where the effective voltage value and reactive power are in regions 5, 6, and 7 at the current moment, set their capacitor capacity to be equal to the capacitor capacity invested at the current moment.

[0094] For the nodes where the effective voltage value and reactive power are in regions 1, 2, 3, 4, 8, 9, 10, and 11 at the current moment, denoted as the third nodes, select a random number within their capacitor capacity intervals at the current moment as their capacitor capacity.

[0095] For the current moment, arrange the capacitor capacities of all nodes in the low-voltage distribution network power system according to the fixed positions of the nodes to form a capacitor capacity vector of the power system, where each element represents the capacitor capacity that the intelligent capacitor needs to invest at each node.

[0096] Using the same method as above, perform multiple random number selections to obtain K different capacitor capacity vectors of the power system at the current moment as the initial population of the subsequent optimization algorithm. In this embodiment, K is taken as 30, and the implementer can set it according to the actual situation.

[0097] S4. Analyze the active power loss of the power system, the switching times of all capacitors, and the distribution of the effective voltage values of each node under the control of each capacitor capacity vector to obtain the fitness corresponding to each capacitor capacity vector.

[0098] The common compensation type intelligent capacitor can perform compensation on three phases simultaneously with the same compensation capacity, and in this embodiment, the common compensation type intelligent capacitors installed at all nodes adopt a cyclic switching strategy in the common compensation mode. According to the process of the cyclic switching of the intelligent capacitor and the capacitor capacity that needs to be invested currently, obtain the switching times of the intelligent capacitors at different nodes under the current switching change.

[0099] Power flow calculation refers to the process of accurately calculating the node voltage distribution in a power system in a given power grid structure, given its network topology and the electrical parameters of lines and nodes. The node topology structure of the low-voltage distribution network power system in this embodiment adopts the topology structure of the IEEE 33-node system. According to the electrical parameters of nodes and lines and the capacitor capacity input by node intelligent capacitors, the effective voltage values of different nodes are obtained through MATLAB / Simulink simulation under different capacitor capacity vectors of the power system. Among them, the power flow calculation method of the power grid in this embodiment adopts the Newton-Raphson method. The simulation process of the power system and the Newton-Raphson method are both well-known existing technologies and will not be elaborated here.

[0100] Taking the active power loss, voltage deviation, and capacitor switching times of the power system as the optimization objectives, an objective function is constructed, specifically:

[0101]

[0102] In the formula, J represents the objective function, and the calculation result of the objective function is used as the fitness. represents the active power loss of the power system; represents the cumulative sum of the differences between the effective voltage values of all nodes and the nominal voltage under the control of each capacitor capacity vector; represents the sum of the switching times of all intelligent capacitors in the power system under the control of each capacitor capacity vector; , , respectively represent three preset weights, satisfying and , in this embodiment , , . Denote as the fusion result.

[0103] It should be noted that the difference represents the degree of difference between two variables, and can be specifically calculated by methods such as the absolute value of the difference, the square of the difference, and the ratio. In this embodiment, the absolute value of the difference is used as the calculation method of the difference; fusion means combining multiple variables, and can be specifically calculated by methods such as addition, multiplication, and a combination of addition and multiplication.

[0104] In this embodiment, the calculation method of the active power loss of the power system is:

[0105]

[0106] Among them, B represents the number of branches in the power system; represents the branch resistance connecting the i-th node and the j-th node of the power system; and denote the effective values of the voltages of the \(i\)-th and \(j\)-th nodes under the control of each capacitor capacity vector; and denote the voltage phases of the \(i\)-th node and the \(j\)-th node; \(\cos()\) represents the cosine function. The calculation of the active power loss of the power system is a known prior art.

[0107] S5. Utilize the distribution of the effective values of the voltages of each node and the reactive power under the control of each capacitor capacity vector, as well as their distributions in the updated eleven-zone diagram, to correct the explosion radius and the number of explosion sparks of each firework in the fireworks algorithm; obtain the current optimal capacitor capacity vector according to the corrected fireworks algorithm and the fitness, and perform switching control on the capacitors.

[0108] Intelligent capacitors are discrete control devices, and frequent switching will affect their service life. The reactive power compensation of the distribution network power system must consider the switching times of the capacitors, and the switching control of the intelligent capacitors at different nodes needs to be carried out separately. Different capacitor switching amounts in the distribution network result in voltage differences between nodes, causing line losses in the power system. Therefore, the intelligent capacitors need to optimize and control multiple objectives such as node voltage, capacitor switching times, and line losses simultaneously.

[0109] The electrical state changes of different nodes in the low-voltage distribution network power system are relatively random, and the influence of different reactive power compensation capacities of each node on multiple optimization objectives is relatively complex. When the fireworks algorithm performs optimization, multiple explosion sparks are generated for each firework by selecting different dimensions. On the one hand, different dimensions of the firework correspond to the capacitor capacities invested in different nodes in the power system, which is convenient for optimizing and controlling the capacitor capacities invested in nodes in different regions of the eleven-zone diagram separately. On the other hand, by generating multiple explosion sparks and Gaussian sparks, the optimization range in each direction is expanded, avoiding the capacitor capacities invested in different nodes falling into local optima in the later stage of iteration.

[0110] The specific process of optimizing the capacitor capacity vector of the power system by using the fireworks algorithm in this embodiment is as follows:

[0111] First, under the control of each capacitor capacity vector, construct a first coordinate with the reactive power and the effective value of the voltage of each node as the first and second components to reflect the electrical state of each node; use the mean value of the upper limit and the lower limit of the reactive power in the eleven-zone diagram as the first component, and the mean value of the upper limit and the lower limit of the voltage as the second component to form a second coordinate as the reference for capacitor switching of nodes in abnormal electrical states.

[0112] Secondly, take the initial population obtained in step S3 as the input, each capacitor capacity vector as a firework in the fireworks algorithm, and use the calculation result of the objective function as the fitness of the capacitor capacity vector to obtain the fitness of each capacitor capacity vector.

[0113] Finally, according to the control strategy of the eleven - zone diagram, in this embodiment, the fireworks algorithm selects the dimensions corresponding to the nodes in zones 1, 2, 3, 4, 8, 9, 10, and 11 in the capacitor capacity vector for optimization, and obtains the fireworks population for the next iteration through the explosion operator. At the same time, to further improve the optimization effect of the fireworks algorithm, according to the advantages and disadvantages of the current power system control effect under different capacitor capacity vectors, the explosion operators of different fireworks are obtained respectively, where the explosion operator is determined by the explosion radius and the number of explosion sparks.

[0114] It should be understood that in order to differentiate fireworks at different positions, improve the optimization ability near fireworks with smaller fitness, and enhance the optimization effect of capacitor switching control, for fireworks with smaller fitness, a smaller explosion radius and a larger number of explosion sparks are set.

[0115] On the other hand, considering the change in the position of the first coordinate of the node in the eleven - zone diagram under the control of different capacitor capacity vectors, in order to reduce the "switching oscillation" of the capacitor, the smaller the metric distance between the first coordinate and the second coordinate obtained after control, the closer the electrical state of the node is to zone 5, and the smaller the probability of subsequent "switching oscillation". A smaller explosion radius and a larger number of explosion sparks are set for the corresponding capacitor capacity vector to improve the optimization effect of the fireworks algorithm.

[0116] At the same time, since the probability of "switching oscillation" of the nodes located in zones 4 and 8 after the control of the capacitor capacity vector is relatively large, the size relationship between them and the local voltage upper limit and the local voltage lower limit is added as an influencing factor for adjusting the explosion operator of the corresponding capacitor capacity vector. When the effective voltage value of the node in zone 4 is closer to the local voltage lower limit, or the effective voltage value of the node in zone 8 is closer to the local voltage upper limit, the probability of "switching oscillation" is greater. Therefore, a larger explosion radius and a smaller number of explosion sparks are set for the corresponding capacitor capacity vector to expand the optimization range and avoid falling into local optima.

[0117] According to the fitness distribution of each firework in the initial population at the current moment, the specific process of calculating the explosion radius and the number of explosion sparks is as follows:

[0118]

[0119]

[0120] In the formula, is the explosion radius of the k - th firework, is the first adjustment factor of the explosion radius of the k - th firework, is the fitness corresponding to the capacitor capacity vector represented by the k - th firework, is the fitness corresponding to the capacitor capacity vector represented by the i - th firework, is the minimum value of the fitness corresponding to all fireworks in the fireworks population. is a preset value greater than 0 to avoid the denominator and numerator being 0. In this embodiment, , which can be set by the implementer according to the actual situation. is the number of fireworks in the fireworks population; is the number of explosion sparks of the k-th firework, and round[] is the rounding function. is the second adjustment factor of the number of explosion sparks of the k-th firework. is the maximum value of the fitness corresponding to all fireworks in the fireworks population.

[0121] and are used to adjust the explosion radius and the number of explosion sparks of the k-th firework. In this embodiment, and The calculation methods are as follows:

[0122]

[0123]

[0124] In the formula, L is the number of nodes where the reactive power and the effective value of the voltage are in regions 1, 2, 3, 4, 8, 9, 10, and 11 under the control of the capacitor capacity vector represented by the k-th firework, that is, the number of corresponding third nodes. F and R respectively represent the number of nodes where the reactive power and the effective value of the voltage are in regions 4 and 8 under the control of the capacitor capacity vector represented by the k-th firework, that is is the number of nodes in the third node where the reactive power is less than the lower limit of the reactive power in the eleven-region diagram and the effective value of the voltage is greater than the local voltage lower limit and less than the voltage upper limit in the eleven-region diagram. is the number of nodes in the third node where the reactive power is greater than the upper limit of the reactive power in the eleven-region diagram and the effective value of the voltage is greater than the voltage lower limit in the eleven-region diagram and less than the local voltage upper limit. , and respectively represent the metric distances between the first and second coordinates of its g-th, f-th, and r-th nodes. , are respectively the differences between the effective values of the voltages of the f-th and r-th nodes and the local voltage lower limit.

[0125] It should be noted that in this embodiment, the Euclidean distance is used to calculate the measurement distance. Implementers can choose other existing feasible measurement distance calculation methods by themselves, such as Manhattan distance, DTW distance, etc. In this embodiment, the maximum number of iterations of the fireworks algorithm is set to 200 times, which can be set by the implementer himself. The output of the fireworks algorithm is the optimal capacitor capacity vector, and the corresponding shunt-type intelligent capacitors installed at the corresponding nodes are controlled according to each component in the optimal capacitor capacity vector and the cyclic switching strategy, so as to complete the switching control of the capacitors. The flowchart for obtaining the optimal capacitor capacity vector is as shown in Figure 3 shown. Among them, the fireworks algorithm is a well-known existing technology, and the specific process will not be elaborated in detail here.

[0126] Based on the same inventive concept as the above method, an embodiment of the present application also provides a switching control system for capacitors, including a memory, a processor, and a computer program stored in the memory and running on the processor. When the processor executes the computer program, it implements the steps of any one of the above methods for switching control of a capacitor.

[0127] It should be noted that the above sequence of embodiments of the present application is only for description and does not represent the superiority or inferiority of the embodiments. And the above description of specific embodiments of this specification has been made. In addition, the processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0128] Each embodiment in this specification is described in a progressive manner. The same or similar parts among the embodiments can be referred to each other, and the key points of each embodiment are the differences from other embodiments.

[0129] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the principle of the present application shall be included in the protection scope of the present application.

Claims

1. A capacitor switching control method, characterized in that: The method comprises the following steps: Through the voltage and current data of each node at each time and its adjacent time in the power system, the effective value of voltage and reactive power of each node at each time are obtained; Obtain a nine-area diagram in the power system; add a preset local voltage upper limit and a local voltage lower limit to the nine-area diagram, and correct the nine-area diagram to an eleven-area diagram; preset update cycles, for the start time of any update cycle, obtain a node whose reactive power is greater than the reactive power upper limit in the eleven-area diagram, and whose voltage effective value is greater than the preset local voltage upper limit and less than the voltage upper limit in the eleven-area diagram, and is recorded as a first node; for each first node, determine the difference between the voltage upper limit in the eleven-area diagram and the local voltage upper limit of the previous update cycle of any update cycle, recorded as the first difference, and the difference between the reactive power at the start time of any update cycle and the reactive power upper limit in the eleven-area diagram, recorded as the second difference, and obtain each first node of any update cycle The local voltage upper limit rising adjustment amount of each first node in any update cycle is obtained by combining the local voltage upper limit rising adjustment amount, the local voltage upper limit falling adjustment amount, and the local voltage upper limit of the previous update cycle of any update cycle to determine the corrected local voltage upper limit of each first node in any update cycle; Correspondingly, for the starting time of any update period, the node whose reactive power is less than the reactive power lower limit in the eleven-zone diagram and whose voltage effective value is less than the preset local voltage lower limit and greater than the voltage lower limit in the eleven-zone diagram is recorded as the second node, and the corrected local voltage lower limit of each second node in any update period is determined; Further, the updated eleven-area graph of each node in each update cycle is obtained; Combine the current capacitor capacity of each node and the distribution of the current voltage effective value and reactive power of each node in the updated eleven-zone map, and randomly generate the capacitor capacity of each node; combine the capacitor capacities of all nodes in the power system into a capacitor capacity vector; accordingly, obtain multiple capacitor capacity vectors; Analyze the active network loss of the power system, the switching times of all capacitors, and the distribution of the effective value of the voltage of each node under the control of each capacitor capacity vector on all nodes, and obtain the fitness corresponding to each capacitor capacity vector; The explosion radius and the number of explosion sparks of each firework in the fireworks algorithm are corrected by utilizing the voltage effective value and reactive power distribution of each node under the control of each capacitor capacity vector and its distribution in the updated eleven-zone diagram; the current optimal capacitor capacity vector is obtained according to the corrected fireworks algorithm and the fitness, and the capacitor is switched on and off.

2. A capacitor switching control method as claimed in claim 1, characterized in that: The determination of the corrected local voltage upper limit includes: The corrected local voltage upper limits of each first node in any update cycle are positively correlated with the local voltage upper limit increase adjustment amount and the local voltage upper limit in the previous update cycle of any update cycle, and are negatively correlated with the local voltage upper limit decrease adjustment amount; For each node in the power system except the first node in any update period, the corrected local voltage upper limit remains the same as the local voltage upper limit in the previous update period of any update period.

3. A capacitor switching control method as claimed in claim 1, characterized in that: The determination of the corrected local voltage lower limit includes: For each second node, the third difference and the discreteness are calculated, and the proportion of the time during which the effective voltage value is greater than the local voltage lower limit in the update cycle before any update cycle in the entire update cycle is calculated; Combining the third difference, the discrete degree, and the proportion of each second node, obtaining a local voltage lower limit rise adjustment amount of each second node in any update period; For each second node, the difference between the local voltage lower limit of the previous update cycle of any update cycle and the voltage lower limit in the eleven-zone diagram is calculated, recorded as a fourth difference, and the difference between the reactive power lower limit in the eleven-zone diagram and the reactive power at the start time of any update cycle is calculated, recorded as a fifth difference; Combining the fourth difference with the fifth difference, obtaining a lower limit decrease adjustment amount of the local voltage of each second node in any update period; The corrected local voltage lower limits of each second node in any update cycle are positively correlated with the local voltage lower limit increase adjustment amount and the local voltage lower limit of the previous update cycle of any update cycle, and are negatively correlated with the local voltage lower limit decrease adjustment amount.

4. A capacitor switching control method as claimed in claim 1, characterized in that: The determination of the capacitor capacity of each node includes: For each first node and each second node at the current moment, and for nodes whose reactive power at the current moment is greater than the lower limit of reactive power and less than the upper limit of reactive power in the eleven-zone diagram, and whose voltage effective value is greater than the lower limit of voltage in the eleven-zone diagram and less than the upper limit of voltage in the eleven-zone diagram, set the capacitor capacity equal to the capacitor capacity put into use at the current moment; Each remaining node at the current moment is recorded as a third node, and the ideal capacitor capacity of each third node is calculated. The interval formed by the capacitor capacity of each third node at the current moment and its ideal capacitor capacity is obtained, and a random number is selected within the interval as the capacitor capacity of each third node.

5. A capacitor switching control method as claimed in claim 1, characterized in that: The obtaining of the fitness corresponding to each capacitor capacity vector includes: Calculate the cumulative sum of the differences between the effective voltage values ​​of all nodes and the nominal voltage under the control of each capacitor capacity vector; calculate the sum of the switching times of all capacitors under the control of each capacitor capacity vector; The fitness corresponding to each capacitor capacity vector is a fusion result of the cumulative sum, the sum of the switching times, and the active network loss of the power system under preset weights.

6. A capacitor switching control method as claimed in claim 4, characterized in that: The determination of the explosion radius includes: The reactive power and voltage effective value of each node under the control of each capacitor capacity vector form a first coordinate, and the average of the reactive power upper limit and the reactive power lower limit in the eleven-zone diagram, and the average of the voltage upper limit and the voltage lower limit form a second coordinate; Based on the distribution of reactive power and voltage effective value of each node in the eleven-area diagram under the control of each capacitor capacity vector, and the distance between the first coordinate and the second coordinate of each node, a first adjustment factor of the explosion radius is determined; The explosion radius is calculated as follows: ; In the formula, is the explosion radius of the kth firework, is the first adjustment factor of the explosion radius of the kth firework, is the fitness corresponding to the capacitor capacity vector represented by the kth firework, is the fitness corresponding to the capacitor capacity vector represented by the i-th firework, is the minimum value of the fitness corresponding to all fireworks in the fireworks population, To preset a value greater than 0, is the number of fireworks in the fireworks population.

7. A capacitor switching control method as claimed in claim 6, characterized in that: The calculation method of the first adjustment factor of the explosion radius is: ; Wherein, L is the number of the third nodes under the control of the capacitor capacity vector represented by the kth firework, is the number of nodes in the third node whose reactive power is less than the lower limit of reactive power in the eleven-zone diagram, and whose voltage effective value is greater than the local voltage lower limit and less than the upper limit of voltage in the eleven-zone diagram, is the number of nodes in the third node whose reactive power is greater than the upper limit of reactive power in the eleven-zone diagram, and whose voltage effective value is greater than the lower limit of voltage in the eleven-zone diagram and less than the upper limit of local voltage, , and Respectively represent the metric distance between the first coordinate and the second coordinate of the g-th, f-th, and r-th nodes, , They are the differences between the effective values ​​of the voltages at the f-th and r-th nodes and the lower limit of the local voltage, respectively.

8. A capacitor switching control method as claimed in claim 7, characterized in that: The determination of the number of explosion sparks includes: Using the same analysis method as the first adjustment factor of the explosion radius, a second adjustment factor of the number of explosion sparks is obtained; The calculation method of the number of explosion sparks is: ; In the formula, is the number of explosion sparks of the kth firework, round[] is the rounding function, is the second adjustment factor for the number of explosion sparks of the kth firework, It is the maximum value of the fitness corresponding to all fireworks in the fireworks population.

9. A capacitor switching control method as claimed in claim 8, characterized in that: The calculation method of the second adjustment factor of the number of explosion sparks is: .

10. A capacitor switching control system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are implemented.

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