Capacitor switching control method and system

Abstract

The invention relates to the technical field of capacitor switching control, in particular to a capacitor switching control method and system, and the method comprises the steps: obtaining the voltage effective value and reactive power of each node at each moment through the voltage and current data of each node at each moment and adjacent moments in a power system; acquiring a nine-zone diagram in the power system; adding a local voltage upper limit and a local voltage lower limit in the nine-area graph, and correcting the nine-area graph into an eleventh-area graph; acquiring the corrected local voltage upper limit and local voltage lower limit of each node in each updating period; obtaining an eleven-area graph after each node is updated in each updating period; obtaining a plurality of capacitor capacity vectors; determining fitness corresponding to each capacitor capacity vector; correcting the explosion radius and the explosion spark number of each firework in the firework algorithm; and obtaining a current optimal capacitor capacity vector according to the corrected fireworks algorithm and the fitness, and carrying out switching control on the capacitor. Therefore, 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 in particular to a capacitor switching control method and system. Background Art

[0002] The characteristics of variable inductive loads and high operating losses in low-voltage distribution networks result in frequent low power factor and reactive power imbalance. The compensation equipment of low-voltage distribution networks generally works in an environment with variable power factor and no one to monitor it. Therefore, it is required that the compensation equipment in the low-voltage distribution network can automatically perform switching control according to the compensation requirements. As a static reactive power compensation device, the intelligent capacitor divides the switched capacitors into multiple groups, controls the switching according to the reactive power changes of the power grid, and realizes flexible adjustment of the reactive power compensation amount to ensure that the node voltage does not exceed the limit.

[0003] Smart capacitors are discrete control devices, and frequent switching will affect their lifespan. The reactive power compensation of the distribution network power system must take into account the number of capacitor switching times, and the smart capacitors at different nodes need to be switched on and off separately. Different capacitor switching amounts in the distribution network lead to differences in voltage between nodes, resulting in line network losses in the power system. Therefore, smart capacitors need to consider optimizing and controlling multiple objectives such as node voltage, capacitor switching times, and line network losses at the same time. Since the electrical state of the low-voltage distribution network power system changes randomly, the existing capacitor switching control method has poor optimization effect on multi-objective reactive power compensation. Summary of the invention

[0004] In order to solve the above technical problems, the purpose of this application is to provide a capacitor switching control method and system, and the technical solutions adopted are as follows: In a first aspect, an embodiment of the present application provides a capacitor switching control method, the method comprising 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 an update cycle, analyze the distribution of the voltage effective value and reactive power of each node in the eleven-area diagram at the start time of each update cycle, and the distribution of the voltage effective value and reactive power of each node in the adjacent update cycle of each update cycle, and obtain the corrected local voltage upper limit and local voltage lower limit of each node in each update cycle; further obtain the updated eleven-area diagram of each node in each update cycle; 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.

[0005] In one embodiment, the determination of the corrected local voltage upper limit and the local voltage lower limit includes: At the start time of any update cycle, 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 is recorded as the first node; For each first node, the difference between the upper voltage limit in the eleven-zone diagram and the upper local voltage limit in the previous update cycle of any update cycle is calculated, recorded as the first difference, and the difference between the reactive power at the start time of any update cycle and the upper reactive power limit in the eleven-zone diagram is calculated, recorded as the second difference; Combining the first difference and the second difference, obtaining a local voltage upper limit rise adjustment amount of each first node in any update period; For each first node, calculate the difference between the local voltage upper limit and the local voltage lower limit in the previous update cycle of any update cycle, record it as the third difference, calculate the discrete degree of the voltage effective value at all times in the previous update cycle of any update cycle, and calculate the proportion of the time when the voltage effective value in the previous update cycle of any update cycle is less than the local voltage upper limit in the entire update cycle; Combining the third difference, the discrete degree and the ratio, obtaining a local voltage upper limit decrease adjustment amount of each first node in any update period; 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 except the first node in any one update cycle, the corrected local voltage upper limit remains the same as the local voltage upper limit in the previous update cycle of any one update cycle; Based on the same analysis method as the corrected upper limit of the local voltage of each node in any update period, the corrected lower limit of the local voltage of each node in any update period is obtained.

[0006] In one embodiment, the determination of the corrected local voltage lower limit of each node in any update period includes: At the start time of any update cycle, a 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; 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 increase 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.

[0007] In one embodiment, 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.

[0008] In one embodiment, obtaining 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.

[0009] In one embodiment, 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.

[0010] In one embodiment, the first adjustment factor of the explosion radius is calculated as follows: ; 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.

[0011] In one embodiment, 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.

[0012] In one embodiment, the second adjustment factor of the number of explosion sparks is calculated as follows: .

[0013] In a second aspect, an embodiment of the present application further provides a capacitor switching control system, comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor implements the steps of any one of the above methods when executing the computer program.

[0014] This application has at least the following beneficial effects: The present application obtains the voltage effective value and reactive power of each node at each moment through the voltage and current data of each node at each moment and its adjacent moments in the power system; obtains a nine-zone diagram in the power system; adds a preset local voltage upper limit and 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; preset update cycles, analyze the distribution of the voltage effective value and reactive power of each node in the eleven-zone diagram at the start time of each update cycle, and the distribution of the voltage effective value and reactive power of each node in the adjacent update cycle of each update cycle, and obtain the corrected local voltage upper limit and local voltage lower limit of each node in each update cycle; avoids the disadvantage that the fixed local voltage upper limit and local voltage lower limit in the eleven-zone diagram have insufficient improvement effect on the phenomenon of "switching oscillation" of capacitors, reduces the probability of occurrence of the "switching oscillation" phenomenon of capacitors, and further obtains the updated eleven-zone diagram of each node in each update cycle; combines the current capacitor capacity of each node, and the current voltage effective value and reactive power distribution of each node in the updated eleven-zone diagram, randomly generates the capacitor capacity of each node; The capacitor capacities of all nodes form a capacitor capacity vector; accordingly, multiple capacitor capacity vectors are obtained and used as optimization variables of the fireworks algorithm; the active network loss of the power system, the number of 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 are analyzed 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 final optimized capacitor capacity is improved, and the reactive power compensation effect in the power system is improved; the explosion radius and the number of explosion sparks of each firework in the fireworks algorithm are corrected by using the distribution of the effective value of the voltage and reactive power of each node under the control of each capacitor capacity vector, and the distribution in the updated eleven-zone map; the suitability of the explosion radius and the number of explosion sparks of each firework is improved, and finally the optimization effect of the fireworks algorithm is provided; the current optimal capacitor capacity vector is obtained according to the corrected fireworks algorithm and the fitness, and the switching of the capacitor is controlled, so as to avoid the "switching oscillation" phenomenon caused by frequent switching of the capacitor, extend the service life of the capacitor, and improve the reactive power compensation effect of the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present application or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0016] Figure 1A flowchart of a capacitor switching control method provided in one embodiment of the present application; Figure 2 It is a schematic diagram of the eleven-area map; Figure 3 Obtain a flow chart for the optimal capacitor capacity vector. DETAILED DESCRIPTION

[0017] In order to further explain the technical means and effects adopted by the present application to achieve the predetermined invention purpose, the following is a detailed description of a capacitor switching control method and system proposed in the present application, its specific implementation, structure, features and effects, in combination with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "another embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures or characteristics in one or more embodiments may be combined in any suitable form.

[0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

[0019] The specific scheme of a capacitor switching control method and system provided by the present application is described in detail below with reference to the accompanying drawings.

[0020] See also Figure 1 , which shows a flow chart of a capacitor switching control method provided by an embodiment of the present application, the method comprising the following steps: S1, obtain the voltage effective value and reactive power of each node at each moment through the voltage and current data of each node at each moment and its adjacent moments in the power system.

[0021] In this embodiment, the voltage data and current data of each node in the power system are collected by intelligent capacitors, wherein the collection frequency of the voltage data and the current data are both 1024 Hz, and the voltage data at each moment and the 1023 adjacent voltage data before it are combined into a voltage sequence at each moment in time sequence, that is, the voltage sequence at each moment contains 1024 voltage data, and the duration of the voltage sequence at each moment is 1 s. The same acquisition method of the voltage sequence at each moment is adopted, and the current sequence at each moment is obtained for the current data, and the capacitor capacity currently invested in each node is obtained at each moment.

[0022] It should be noted that the implementer can set the frequency of collecting voltage data and current data according to the actual situation, and this embodiment does not limit it. This embodiment adopts a common compensation type intelligent capacitor and uses a magnetic holding relay as a switching switch to monitor the electrical status of the node at all times and perform capacitor group switching operations when there is an abnormality in the node.

[0023] The voltage sequence and current sequence of each node at each time are used as input, and the FFT (Fast Fourier Transformation) algorithm is used to calculate the effective value of voltage, reactive power and active power of each node at each time. The FFT algorithm and the calculation of the effective value of voltage, reactive power and active power of each node are existing well-known technologies, and the specific process will not be repeated.

[0024] S2, obtaining a nine-area diagram in the power system; adding a preset local voltage upper limit and local voltage lower limit to the nine-area diagram, and correcting the nine-area diagram to an eleven-area diagram; presetting an update cycle, analyzing the distribution of the effective value of voltage and reactive power of each node in the eleven-area diagram at the start time of each update cycle, as well as the distribution of the effective value of voltage and reactive power of each node in the adjacent update cycle of each update cycle, to obtain the corrected local voltage upper limit and local voltage lower limit of each node in each update cycle; further obtaining the updated eleven-area diagram of each node in each update cycle.

[0025] The duration of N consecutive voltage sequences is used as the cycle for adjusting the capacitor switching control strategy, and is recorded as an update cycle of the smart capacitor. In this embodiment, N is set to 30, and the implementer can set it according to the actual situation. This embodiment does not limit it. So far, N voltage effective values, N reactive powers, and N active powers of each node in the update cycle are obtained.

[0026] In the power system, the nine-zone diagram divides the operating status of the node into nine areas according to the effective value of the node voltage and reactive power, and then adopts different control methods to switch the capacitor group according to the situation in each area, so as to stabilize the grid voltage and reactive power within the normal range. The nine-zone diagram method is an existing well-known technology, and the specific process will not be described in detail.

[0027] The eleven-zone diagram adds local voltage upper limits and local voltage lower limits to the nine-zone diagram to reduce "switching oscillations". However, the electrical state changes of nodes in the low-voltage distribution network are relatively random, and the fixed local voltage upper limits and local voltage lower limits in the eleven-zone diagram have limited effects on reducing the "switching oscillations" of smart capacitors. Therefore, this embodiment adjusts the eleven-zone diagrams of different nodes in the power system in real time through the effective voltage value and reactive power within the update cycle of each node to further reduce the probability of "switching oscillations". Among them, the schematic diagram of the eleven-zone diagram is shown as follows Figure 2 As shown, Figure 2 Where 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, and U L is the local voltage lower limit, U His the upper limit of the local voltage. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 represent 11 regions respectively. The control strategy of the capacitor corresponding to the eleven-region diagram is shown in Table 1.

[0028] Table 1 Control strategy of capacitors corresponding to the eleven-zone diagram In this embodiment, the voltage upper limit Umax, voltage lower limit Umin, reactive power upper limit Qmax, reactive power lower limit Qmin, local ...min, reactive power upper limit Qmax, reactive power lower limit Qmin, local voltage upper limit Umin, reactive power upper limit Umin, reactive power upper limit Umin, reactive power upper limit Umin, reactive power upper limit Umin, reactive power upper limit Umin, reactive power upper limit Umin H 、Local voltage lower limit U L The specific acquisition process is as follows: First, according to GB12325-2008 Power Quality - Supply Voltage Deviation: The three-phase supply voltage deviation of 20kV and below is ±7% of the nominal voltage, and the voltage upper and lower limits of the eleven-zone diagram are set accordingly. In this embodiment, the nominal voltage is 220V, the voltage upper limit Umax is set to 235V (+7%), the voltage lower limit Umin is set to 205V (-7%), and the initial local voltage upper limit U H =231V(+5%), initial local voltage lower limit U L =209V(-5%), the upper limit and lower limit of initial local voltage can be set by the implementer.

[0029] Secondly, this embodiment adopts the automatic selection method to set the reactive power upper limit Qmax and the reactive power lower limit Qmin of the eleven-zone diagram. The automatic selection method to set the reactive power upper and lower limits is an existing well-known technology and will not be described in detail here.

[0030] Finally, considering the changes in inductive loads at various nodes in the low-voltage distribution network power system at different operating stages, when the node is at the boundary between zone 6 and zone 8 and zone 4 and zone 7, the smart capacitor is prone to "switching oscillation". Therefore, for the nodes whose voltage effective value and reactive power are in zone 6 and zone 7 at the start of each update cycle, the local voltage upper limit and local voltage lower limit of the eleven-zone diagram are adjusted. The specific calculation method is as follows: 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.

[0031] 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.

[0032] 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: ; 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.

[0033] The specific calculation method of the local voltage upper limit increase adjustment amount and the local voltage upper limit decrease adjustment amount is: 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.

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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: ; 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.

[0038] The specific calculation method of the local voltage lower limit increase adjustment amount and the local voltage lower limit decrease adjustment amount is: 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 value of the voltage of each second node in the t-1th update cycle is greater than The proportion of maintenance time to the entire update cycle; represents the difference between the reactive power lower limit in the eleven-zone diagram and the reactive power at the start time of each second node in the tth update cycle; norm() is the normalization function. Recorded as the fourth difference, Recorded as the fifth difference.

[0039] For the remaining nodes except the first node in the tth update cycle, the local voltage upper limit remains the same as that in the t-1th update cycle, and for the remaining nodes except the second node in the tth update cycle, the local voltage lower limit remains the same as that in the t-1th update cycle. The local voltage upper limit and local voltage lower limit obtained for each node in the tth update cycle are used as the corrected local voltage upper limit and local voltage lower limit of each node in the tth update cycle, and then the updated eleven-zone diagram of each node in the tth update cycle is obtained.

[0040] S3, randomly generate the capacitor capacity of each node based on 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 diagram; form a capacitor capacity vector with the capacitor capacities of all nodes in the power system; and accordingly, obtain multiple capacitor capacity vectors.

[0041] This embodiment determines the ideal capacitor capacity of the intelligent capacitor at each node by the power factor. According to the reactive power, active power and ideal power factor of each node of the power system, the ideal capacitor capacity required to be invested at each node is calculated. In order to ensure the maximum improvement of the power factor, the ideal power factor is set in the range of 0.95~0.99, where the ideal power factor in this embodiment is 0.99. The method of calculating the ideal capacitor capacity according to the reactive power, active power and ideal power factor of each node at each time is a well-known technology and will not be repeated here.

[0042] Considering the variable characteristics of inductive loads in low-voltage distribution networks, when the active power and reactive power of nodes fluctuate greatly, controlling the reactive compensation of intelligent capacitors with ideal capacitor capacity can easily cause repeated capacitor action and reduce the service life of capacitors. Therefore, the capacitor capacity range of each node is constructed as the optimization range for the subsequent switching control of its capacitor bank, specifically: When the ideal capacitor capacity is greater than the current smart capacitor capacity put into the node, the current smart capacitor capacity put into the node is used as the left endpoint of the interval, and the ideal capacitor capacity of the node is used as the right endpoint of the interval to construct a closed interval as the capacitor capacity interval of the node; When the ideal capacitor capacity is smaller than the capacitor capacity of the current smart capacitor put into the node, the capacitor capacity of the current smart capacitor put into the node is used as the right endpoint of the interval, and the ideal capacitor capacity of the node is used as the left endpoint of the interval to construct a closed interval as the capacitor capacity interval of the node.

[0043] When the ideal capacitor capacity is equal to the capacitor capacity of the current smart capacitor invested in the node, the capacitor capacity interval degenerates into a point, indicating that the capacitor capacity invested in the node at this time is already in an ideal state and no operation is required.

[0044] This embodiment constructs a capacitor capacity vector of the power system according to the positions of different nodes in the low-voltage distribution network power system in their respective eleven-zone diagrams at the current moment, specifically: For nodes whose voltage effective value and reactive power are in zones 5, 6, and 7 at the current moment, the capacitor capacity is set equal to the capacitor capacity put into use at the current moment.

[0045] For the nodes whose voltage effective value and reactive power are in zones 1, 2, 3, 4, 8, 9, 10, and 11 at the current moment, they are recorded as the third nodes, and a random number is selected within the capacitor capacity interval at the current moment as their capacitor capacity.

[0046] At the current moment, the capacitor capacities of all nodes in the low-voltage distribution network power system are arranged according to the fixed positions of the nodes to form a capacitor capacity vector of the power system, in which each element represents the capacitor capacity required by the smart capacitor at each node.

[0047] The same method as above is adopted to 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, the value of K is 30, and the implementer can set it according to the actual situation.

[0048] S4, analyze the active network loss of the power system, the number of 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.

[0049] The co-compensation type intelligent capacitor can compensate three phases at the same time with the same compensation capacity, and the co-compensation type intelligent capacitors installed at all nodes in this embodiment adopt a cyclic switching strategy under the co-compensation mode. According to the cyclic switching process of the intelligent capacitor and the current capacitor capacity to be invested, the switching times of the intelligent capacitors at different nodes under the current switching changes are obtained.

[0050] Power flow calculation refers to the process of accurately calculating the voltage distribution of nodes in the power system in a given power grid structure, given the network topology and the electrical parameters of the lines and nodes. The node topology of the low-voltage distribution network power system of this embodiment adopts the topology of the IEEE 33-node system. According to the electrical parameters of the nodes and lines and the capacitor capacity of the node intelligent capacitors, the voltage effective values ​​of different nodes under the control of different capacitor capacity vectors of the power system are obtained through MATLAB / Simulink simulation. 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 existing well-known technologies and will not be repeated here.

[0051] Taking the active network loss, voltage deviation and capacitor switching times of the power system as the optimization targets, the objective function is constructed, which is as follows: In the formula, J represents the objective function, and the calculated result of the objective function is used as the fitness. Indicates the active network loss of the power system; It 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; It represents the sum of the switching times of all intelligent capacitors in the power system under the control of the capacitor capacity vector; , , Represent three preset weights respectively, satisfying and In this embodiment , , .Will Recorded as the fusion result.

[0052] It should be noted that the difference represents the degree of difference between two variables, which can be calculated by the absolute value of the difference, the square of the difference, the ratio, etc. This embodiment uses the absolute value of the difference as the calculation method of the difference; fusion means combining multiple variables, which can be calculated by addition, multiplication, or a mixture of addition and multiplication.

[0053] In this embodiment, the calculation method of the active network loss of the power system is: Where 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 represents the effective value of the voltage at the i-th and j-th nodes under the control of the capacitance vector of each capacitor; and represents the voltage phase between the ith node and the jth node; cos() represents the cosine function. The calculation of active network loss of the power system is a known technology.

[0054] S5, using the distribution of the effective value of the voltage and reactive power of each node under the control of each capacitor capacity vector, as well as the distribution in the updated eleven-zone diagram, to correct the explosion radius and the number of explosion sparks of each firework in the fireworks algorithm; according to the corrected fireworks algorithm and the fitness, the current optimal capacitor capacity vector is obtained to control the switching of the capacitor.

[0055] Smart capacitors are discrete control devices, and frequent switching will affect their lifespan. Reactive compensation of the power distribution network must take into account the number of capacitor switching times, and the smart capacitors at different nodes must be switched on and off separately. Different capacitor switching amounts in the distribution network lead to differences in voltage between nodes, resulting in line network losses in the power system. Therefore, smart capacitors need to optimize and control multiple targets simultaneously, including node voltage, capacitor switching times, and line network losses.

[0056] The electrical state changes of different nodes in the low-voltage distribution network power system are relatively random, and the influence of different reactive compensation capacities of each node on multiple optimization objectives is relatively complex. When the fireworks algorithm is searching for the best, it selects different dimensions for each firework to generate multiple explosion sparks. On the one hand, the different dimensions of the fireworks correspond to the capacitor capacities of different nodes in the power system, which facilitates the optimization control of the capacitor capacities of nodes in different areas of the eleven-zone diagram. On the other hand, by generating multiple explosion sparks and Gaussian sparks, the optimization range in all directions is expanded, avoiding the capacitor capacities of different nodes falling into local optimality in the later stages of iteration.

[0057] The specific process of optimizing the capacitor capacity vector of the power system using the fireworks algorithm in this embodiment is as follows: Firstly, under the control of the capacity vector of each capacitor, the reactive power and the effective value of the voltage of each node are used as the first and second components to construct the first coordinate to reflect the electrical state of each node; the mean of the upper limit and the lower limit of the reactive power in the eleven-zone diagram is used as the first component, and the mean of the upper limit and the lower limit of the voltage is used as the second component to form the second coordinate as a reference for switching on and off the capacitors at the nodes in abnormal electrical state.

[0058] Secondly, the initial population obtained in step S3 is used as input, each capacitor capacity vector is a firework in the fireworks algorithm, and the calculation result of the objective function is used as the fitness of the capacitor capacity vector to obtain the fitness of each capacitor capacity vector.

[0059] Finally, according to the control strategy of the eleven-zone diagram, the fireworks algorithm in this embodiment selects the dimensions corresponding to the nodes in zones 1, 2, 3, 4, 8, 9, 10, and 11 in the capacitor capacity vector as optimization, and obtains the fireworks population for the next iteration through the explosion operator. At the same time, in order to further improve the optimization effect of the fireworks algorithm, according to the advantages and disadvantages of different capacitor capacity vectors on the control effect of the current power system, 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.

[0060] It should be understood that in order to differentiate fireworks at different positions, improve the ability to find the best fit near fireworks with lower fitness, and enhance the optimization effect of capacitor switching control, a smaller explosion radius and a larger number of explosion sparks are set for fireworks with lower fitness.

[0061] 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 measured 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.

[0062] At the same time, since the probability of "switching oscillation" is high at the nodes located in zones 4 and 8 after the capacitor capacity vector is controlled, the size relationship between the nodes 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 value of the voltage at the node in zone 4 is closer to the local voltage lower limit, or the effective value of the voltage at 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 the local optimum.

[0063] 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: 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 to avoid the denominator and numerator being 0, in this embodiment , implementers can set it according to actual conditions. is the number of fireworks in the fireworks population; 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.

[0064] and It is used to adjust the explosion radius of the kth firework and the number of explosion sparks. In this embodiment, and The calculation method is: Where L is the number of nodes whose reactive power and voltage effective values ​​are in zones 1, 2, 3, 4, 8, 9, 10, and 11 under the control of the capacitor capacity vector represented by the kth firework, that is, the number of nodes corresponding to the third node. F and R represent the number of nodes whose reactive power and voltage effective values ​​are in zones 4 and 8 under the control of the capacitor capacity vector represented by the kth firework, respectively. 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.

[0065] It should be noted that in this embodiment, the metric distance is calculated using the Euclidean distance. The implementer can choose other existing feasible metric distance calculation methods, 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. The output of the fireworks algorithm is the optimal capacitor capacity vector, and the co-complementary smart capacitor installed at the corresponding node is controlled according to each component in the optimal capacitor capacity vector and the cyclic switching strategy to complete the switching control of the capacitor. The optimal capacitor capacity vector acquisition flow chart is shown in the figure. Figure 3 As shown, the fireworks algorithm is an existing well-known technology, and the specific process will not be described in detail here.

[0066] Based on the same inventive concept as the above method, an embodiment of the present application also provides a capacitor switching control system, including a memory, a processor, and a computer program stored in the memory and running on the processor, and when the processor executes the computer program, the steps of any one of the above-mentioned capacitor switching control methods are implemented.

[0067] It should be noted that the above sequence of the embodiments of the present application is for description only and does not represent the advantages and disadvantages of the embodiments. The above is a description of a specific embodiment of this specification. In addition, the processes depicted in the accompanying drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0068] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments.

[0069] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the principles of the present application should 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: The voltage effective value and reactive power of each node at each time are obtained through the voltage and current data of each node at each time and its adjacent time in the power system; 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 an update cycle, analyze the distribution of the voltage effective value and reactive power of each node in the eleven-area diagram at the start time of each update cycle, and the distribution of the voltage effective value and reactive power of each node in the adjacent update cycle of each update cycle, and obtain the corrected local voltage upper limit and local voltage lower limit of each node in each update cycle; further obtain the updated eleven-area diagram of each node in each update cycle; 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 and the local voltage lower limit includes: At the start time of any update cycle, 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 is recorded as the first node; For each first node, the difference between the upper voltage limit in the eleven-zone diagram and the upper local voltage limit in the previous update cycle of any update cycle is calculated, recorded as the first difference, and the difference between the reactive power at the start time of any update cycle and the upper reactive power limit in the eleven-zone diagram is calculated, recorded as the second difference; Combining the first difference and the second difference, obtaining a local voltage upper limit rise adjustment amount of each first node in any update period; For each first node, calculate the difference between the local voltage upper limit and the local voltage lower limit in the previous update cycle of any update cycle, record it as the third difference, calculate the discrete degree of the voltage effective value at all times in the previous update cycle of any update cycle, and calculate the proportion of the time when the voltage effective value in the previous update cycle of any update cycle is less than the local voltage upper limit in the entire update cycle; Combining the third difference, the discrete degree and the ratio, obtaining a local voltage upper limit decrease adjustment amount of each first node in any update period; 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 except the first node in any one update cycle, the corrected local voltage upper limit remains the same as the local voltage upper limit in the previous update cycle of any one update cycle; Based on the same analysis method as the corrected upper limit of the local voltage of each node in any update period, the corrected lower limit of the local voltage of each node in any update period is obtained.

3. A capacitor switching control method as claimed in claim 2, characterized in that: The determination of the corrected local voltage lower limit of each node in any update period includes: At the start time of any update cycle, a 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; 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 3, 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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