A power distribution line dynamic compensation regulation method for preventing voltage fluctuation
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- 国网黑龙江省电力有限公司齐齐哈尔供电公司
- Filing Date
- 2026-03-26
- Publication Date
- 2026-06-23
AI Technical Summary
The existing voltage fluctuation management of power distribution lines mainly relies on static compensation methods, which cannot dynamically track changes in voltage and line loss, resulting in limited regulation capabilities and affecting the safe operation of the power grid and the reliability of electricity use.
By obtaining the voltage deviation, reactive power variation synchronization, and limit coefficient between the trunk node and the compensation point, the reactive power compensation coverage sub-region is divided, and the compensation capacity of the reactive power compensation device is dynamically adjusted in combination with the prediction model to dynamically compensate the power distribution line.
It effectively prevents voltage fluctuations, reduces active power loss and voltage dips, improves overall power quality, and ensures grid stability and reliability.
Smart Images
Figure CN121906525B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of voltage compensation control technology, specifically to a dynamic compensation adjustment method for power distribution lines to prevent voltage fluctuations. Background Technology
[0002] As an important component of the power system, distribution substations face the dual challenges of a surge in renewable energy penetration and increased randomness on both the source and load sides, as well as the rapid development of new power systems based on new energy sources, the large-scale grid connection of distributed new energy sources such as photovoltaics and wind power, and the widespread application of various nonlinear and impulsive loads. Voltage fluctuation problems are becoming increasingly prominent, seriously affecting the safe operation of the power grid and the reliability of electricity use.
[0003] The rapid development of new power systems, primarily based on new energy sources, typically covers residential, commercial, and industrial areas. The number of grid-connected microgrids aggregating distributed power sources and loads at the user side is gradually increasing, forming AC / DC hybrid distribution areas with mutual power support. These areas often have numerous branching distribution lines and significant load variations, leading to voltage fluctuations and high energy losses for users. Currently, managing voltage fluctuations in distribution lines mainly relies on static compensation methods, i.e., compensation using fixed capacity. This method can only preset compensation for specific load conditions and cannot dynamically track changes in distribution line voltage and line losses, thus limiting its adjustment capabilities. Summary of the Invention
[0004] In view of the above, it is necessary to provide a dynamic compensation and adjustment method for power distribution lines to prevent voltage fluctuations. Compared with traditional dynamic compensation and adjustment methods for power distribution lines to prevent voltage fluctuations, this method reduces active power loss and voltage drop, and improves overall power quality.
[0005] The present application proposes a dynamic compensation and adjustment method for power distribution lines to prevent voltage fluctuations, which adopts the following technical solution:
[0006] One embodiment of this application provides a dynamic compensation and adjustment method for power distribution lines to prevent voltage fluctuations, the method comprising the following steps:
[0007] At each moment, the voltage deviation between each trunk node and each compensation point is obtained by analyzing the distribution of three-phase active power at each trunk node and the phase voltage differences between each trunk node and each compensation point in the AC power grid area. The reactive power dynamic change synchronicity between each trunk node and each compensation point is obtained by analyzing the correlation between the dynamic changes of reactive power. The boundary coefficient of each trunk node is obtained by analyzing the reversal characteristics of reactive power flow between each trunk node and its adjacent trunk nodes. These factors are then combined with the voltage deviation and the reactive power... The reactive power compensation synchronization degree divides the AC power grid into reactive power compensation coverage sub-areas dominated by each compensation point; the line loss of each distribution trunk line in each reactive power compensation coverage sub-area is calculated, and the historical line loss at multiple time scales is analyzed and predicted using a prediction model to obtain multi-time scale prediction information; by comparing the instantaneous time scale line loss estimate with the overall prediction level in the multi-time scale prediction information, the compensation parameters of the reactive power compensation device in each reactive power compensation coverage sub-area are obtained, and then the compensation capacity of the reactive power compensation device is corrected to dynamically compensate the distribution lines.
[0008] In one embodiment, the process of obtaining the voltage deviation is as follows:
[0009] Calculate the difference in phase voltage between each main line node and each compensation point;
[0010] The ratio of the active power of each phase at each trunk node to the active power of the three phases is denoted as the power ratio.
[0011] The voltage deviation is positively correlated with all the power ratios corresponding to each trunk node, and is also positively correlated with the difference.
[0012] In one embodiment, the voltage deviation is calculated as follows:
[0013] The difference between the highest and lowest allowable voltages of the main line in the distribution area is recorded as the allowable voltage variation, and the ratio of the difference to the allowable voltage variation is recorded as the absolute voltage deviation.
[0014] Calculate the product of the power ratio of each phase at each trunk node and the absolute voltage deviation.
[0015] The voltage deviation is the sum of the products of the three phases at each trunk node.
[0016] In one embodiment, the process of obtaining the reactive power variation synchronization degree is as follows:
[0017] Based on the changes in reactive power of each phase at each trunk node and each compensation point within a preset time range, obtain the reactive power variation sequence of each phase at each trunk node and each compensation point.
[0018] Calculate the correlation coefficient of the reactive power variation sequence of each phase between each trunk node and each compensation point;
[0019] The reactive power variation synchronization degree is obtained by the correlation coefficient of the three phases between each trunk node and each compensation point.
[0020] In one embodiment, the process of obtaining the boundary coefficient is as follows:
[0021] The reactive power of each phase of each trunk node within a preset time range is arranged in time sequence to form the reactive power sequence of each phase of each trunk node. The difference of the elements at the same position in the reactive power sequence of each phase between each trunk node and its adjacent trunk nodes is calculated to obtain the deviation sequence of each phase between each trunk node and its adjacent trunk nodes. The zero-crossing rate of the deviation sequence of each phase between each trunk node and its adjacent trunk nodes is calculated.
[0022] The limit coefficient is the maximum value of the zero-crossing rates of the three phases between each trunk node and all its adjacent trunk nodes.
[0023] In one embodiment, the process of dividing the reactive power compensation coverage sub-region is as follows:
[0024] Obtain the segmentation threshold of the boundary coefficients of all trunk nodes; by comparing the boundary coefficients of each trunk node with the segmentation threshold, calculate the compensation membership degree of each trunk node relative to each compensation point by using the voltage deviation degree and the reactive power variation synchronization degree in different cases.
[0025] Based on the aforementioned compensation membership degree, a fuzzy clustering algorithm is used to divide the AC power grid area into various reactive power compensation coverage sub-regions.
[0026] In one embodiment, the calculation process for the compensated membership degree is as follows:
[0027] Calculate the difference between 1 and the normalized value of the voltage deviation; use the weighted sum of the difference and the reactive power variation synchronicity as the compensation membership degree; wherein, when the limit coefficient of each trunk node is less than the segmentation threshold, the weights of the difference and the reactive power variation synchronicity are both 1; otherwise, the weight of the difference is the sum of 1 and the limit coefficient, and the weight of the reactive power variation synchronicity is the difference between 1 and the limit coefficient.
[0028] In one embodiment, the process of obtaining the multi-time-scale prediction information is as follows: rolling prediction of the average line loss of each transformer area trunk line at multiple time scales, including preset instantaneous time scales and preset long-term time scales; and summing the average line loss of all transformer area trunk lines in each reactive power compensation coverage sub-area at each time scale as the sub-area line loss prediction value of each reactive power compensation coverage sub-area at each time scale.
[0029] In one embodiment, the process of obtaining the compensation parameters is as follows:
[0030] Calculate the average value of the sub-region line loss estimate for each reactive power compensation coverage sub-region across all time scales;
[0031] The ratio of the average value to the estimated line loss of each reactive power compensation coverage sub-region at the instantaneous time scale is denoted as the parameter compensation coefficient; the compensation parameter and the parameter compensation coefficient are positively correlated.
[0032] In one embodiment, the correction process for the compensation capacity is as follows:
[0033] The product of the compensation parameter and the estimated sub-region line loss of each reactive power compensation coverage sub-region at the instantaneous time scale is denoted as the capacity correction amount; the correction value of the compensation capacity is the sum of the preset initial value of the compensation capacity of the reactive power compensation device and the capacity correction amount.
[0034] This application has at least the following beneficial effects:
[0035] This application introduces active power distribution weights to enable voltage deviation to adaptively reflect the actual load distribution, giving greater attention to heavily loaded phases; by calculating reactive power variation synchronicity, it can effectively capture the dynamic coupling characteristics between distribution lines; considering that at the reactive power flow boundary point, the reactive power polarity of adjacent trunk nodes is easily reversed, and the zero-crossing rate is significantly higher than that of the internal area, the boundary coefficient is obtained, which can accurately identify the boundary of the compensation coverage area, enhance the "conservatism" of the compensation judgment of the boundary node, avoid the reverse adjustment of multiple reactive power sources on the same node, realize dynamic zoning compensation, and effectively prevent voltage fluctuations;
[0036] Furthermore, the instantaneous time scale reflects the immediate reactive power deficit, while the long-term time scale reflects the trend change, taking into account both rapid response and stability. By predicting line losses, it can predict the trend of line loss changes in advance and dynamically adjust the compensation capacity of the reactive power compensation device. It can proactively adjust the compensation output before voltage fluctuations, avoid voltage over-adjustment or oscillation, and reduce the long-distance flow of reactive power on the trunk line by distributing compensation through the reactive power compensation device, thereby reducing active power loss and voltage drop and improving the overall power quality. Attached Figure Description
[0037] To more clearly illustrate the technical solutions and advantages in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0038] Figure 1 A flowchart illustrating the steps of a dynamic compensation and adjustment method for power distribution lines to prevent voltage fluctuations, as provided in this application.
[0039] Figure 2 This is a schematic diagram of a hybrid AC / DC distribution area.
[0040] Figure 3 This is a schematic diagram of the microgrid interconnection interface. Detailed Implementation
[0041] In the description of the embodiments in this application, the words "exemplary," "or," and "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design scheme described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design schemes. Specifically, the use of the words "exemplary," "or," and "for example" is intended to present the relevant concepts in a specific manner.
[0042] Unless otherwise defined, 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. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. It should be understood that, unless otherwise stated, " / " in this application means "or".
[0043] It should also be noted that the terms "first" and "second" in this application are used to distinguish similar objects, rather than to describe a specific order or sequence.
[0044] The following description, in conjunction with the accompanying drawings, details a specific scheme for a dynamic compensation and adjustment method for power distribution lines to prevent voltage fluctuations, as provided in this application.
[0045] This application provides an embodiment of a dynamic compensation and adjustment method for distribution lines to prevent voltage fluctuations. Specifically, it provides the following method for dynamic compensation and adjustment of distribution lines to prevent voltage fluctuations. Please refer to [link to relevant documentation]. Figure 1 The method includes the following steps:
[0046] Step 1: Obtain the phase voltage, phase current and power factor of each phase at each trunk node, as well as the phase voltage, phase current and power factor of each phase at each compensation point of reactive power in the AC power grid area.
[0047] With the rapid development of new power systems based on new energy sources, the number of grid-connected microgrids that aggregate distributed power sources and loads on the user side is gradually increasing, forming AC / DC hybrid distribution areas with mutual power support. This is conducive to improving the absorption efficiency and utilization rate of distributed power sources within the microgrid, and meeting the needs of grid dispatching and user power supply reliability in remote distribution areas.
[0048] A schematic diagram of the AC / DC hybrid distribution area is shown below. Figure 2 As shown, Figure 2 The AC microgrid consists of both photovoltaic (PV) and AC loads, and is interconnected with the grid via circuit breakers and transformers. PV power generation in the AC / DC hybrid distribution area is locally absorbed within the microgrid. Since PV power is DC, an AC / DC converter is needed to convert it to AC for interconnection with the AC microgrid. The DC microgrid consists of charging stations and energy storage, while the DC / DC converter is responsible for adjusting the voltage levels on both sides. A schematic diagram of the microgrid interconnection interface is shown below. Figure 3 As shown, the main function of the microgrid interconnection interface is to coordinate and control the power flow between the AC distribution area and the DC microgrid. Specifically, it consists of two AC / DC converters and one DC / DC converter. The AC port of the AC / DC converter is connected to the AC microgrid, and the DC port of the DC / DC converter is connected to the DC microgrid.
[0049] As the terminal component of the power system, distribution lines are responsible for connecting the power supply end, distribution equipment, and electrical loads. Distribution areas cover a large area, and with the large-scale grid connection of new energy distributed power sources, primarily photovoltaic power generation, the distribution system has transformed from a radial passive network into an active network. This application utilizes distribution area topology identification software to obtain the topology diagram of an AC power grid distribution area, i.e., to obtain the topology diagram of an AC microgrid, and to obtain detailed parameters of distribution components, including the length, model, and unit resistance of the distribution lines, and the installed capacity of reactive power compensation devices.
[0050] The distribution network of the transformer substation adopts a three-phase four-wire system for the main line and a single-phase meter box system for the branch lines. Distribution lines with three phase lines and one neutral line in the AC power grid transformer substation topology diagram are designated as transformer substation trunk lines, and distribution lines with one phase line and one neutral line are designated as transformer substation branch lines. Each tower of the transformer substation trunk line in the AC power grid is considered a trunk line node, and a metering and data acquisition device is installed at each trunk line node to obtain the phase voltage, phase current, and power factor of each phase at each trunk line node.
[0051] Due to the long trunk lines, low current carrying capacity, and high risk of three-phase imbalance in typical low-voltage transformer substation structures with three-phase four-wire main lines and single-phase meter boxes on branch lines, a distributed compensation layout is usually adopted, with reactive power compensation devices centrally installed on the main line. This application designates the common connection point between the reactive power compensation device and the main line as the reactive power compensation point, and installs a metering and acquisition device at the compensation point to obtain the phase voltage, phase current, and power factor of each phase at each compensation point.
[0052] In this embodiment, the sampling frequency of the metering acquisition device is 50Hz. The sampling frequency is preset by the user and can be set by the implementer according to the actual situation. This application does not impose any special restrictions.
[0053] Step 2: At each time point, obtain the voltage deviation between each trunk node and each compensation point by analyzing the distribution of three-phase active power at each trunk node and the phase voltage difference between each trunk node and each compensation point of reactive power in the AC power grid area; obtain the reactive power change synchronization between each trunk node and each compensation point by analyzing the correlation of reactive power dynamic changes between each trunk node and each compensation point; obtain the boundary coefficient of each trunk node by analyzing the reversal characteristics of reactive power flow between each trunk node and its adjacent trunk nodes; and then, by combining the voltage deviation and the reactive power change synchronization, divide the AC power grid area into reactive power compensation coverage sub-areas dominated by each compensation point.
[0054] AC power grid distribution lines have long supply radii and high line impedance. If reactive power compensation devices are only installed at the transformer side for centralized compensation, the long-distance flow of reactive current along the distribution lines will lead to high active power losses and voltage drops, making it difficult to meet the reactive power requirements of distant distribution lines in the AC power grid distribution area. Therefore, multiple reactive power compensation devices are usually installed at key locations along the distribution lines to cancel reactive current at nearby nodes, avoiding long-distance transmission of reactive power along the lines, reducing line losses, and preventing voltage fluctuations.
[0055] Based on the phase voltage, phase current, and power factor of each phase at each trunk node, calculate the active power and reactive power of each phase at each trunk node, as expressed by:
[0056] In the formula, This represents the active power of the x-th phase at a single trunk node; This represents the phase voltage of the x-th phase at a single trunk node; This represents the phase current of the x-th phase at a single trunk node; represents the power factor of the x-th phase of a single trunk node; cos() represents the cosine function;
[0057] In the formula, Let x represent the reactive power of the x-th phase of a single trunk node; sin() represents the sine function; where x takes the values 1, 2, and 3, meaning that a single trunk node has three phases a, b, and c.
[0058] It should be noted that the reason for using 1000 as the denominator in the formula is that the unit of active power in AC power grid areas is usually kW, so the calculation formula is standardized by means of a kW unit.
[0059] Calculate the active and reactive power of each phase at each compensation point according to the calculation methods for the active and reactive power of each phase at each trunk node.
[0060] The essence of a reactive power compensation device is to provide reactive current locally to maintain the voltage of the main line of the distribution area. The reactive power compensation effect of the device decreases with the increase of the line length. However, reactive power compensation devices have different installed capacities, connection locations, and proximity to AC loads, resulting in varying compensation coverage areas. To obtain the topology diagram of the AC power grid distribution area, taking the t-th acquisition time and the relationship between main line node i and compensation point z as an example, the voltage deviation between main line node i and compensation point z is obtained by analyzing the distribution of the three-phase active power at main line node i and the difference in phase voltage between each phase between main line node i and compensation point z. The expression is:
[0061] In the formula, This indicates the voltage deviation between trunk node i and compensation point z; This represents the active power of the x-th phase at trunk node i; This represents the average active power of the three phases at trunk node i. This represents the phase voltage of the x-th phase at trunk node i; Let x represent the phase voltage of the x-th phase at compensation point z; These represent the maximum and minimum allowable voltages of the main line in the distribution area, respectively. According to the national standard GB / T12325-2008 Power Quality - Supply Voltage Deviation, in this embodiment, the maximum and minimum allowable voltages are taken as ±7% of the rated phase voltage, i.e., 235.4V and 204.6V. This indicates the absolute value operation.
[0062] It should be noted that in AC power grid areas, especially in the terminal trunk lines with long power supply radii, the voltage drop will occur due to the impedance of the distribution lines, while the flow of reactive power is the main cause of voltage loss and line active power loss.
[0063] The ratio of the active power of the xth phase to the average active power of the trunk node i is used as the load distribution weight of a single-phase branch line. If the active load of the xth phase distribution branch line in the AC power grid area is large, the current carried by the xth phase will be large and the voltage drop will be serious, and the reactive power compensation device will be needed to achieve a balance. It is the absolute phase voltage deviation between the x-th phase of trunk node i and the x-th phase of compensation point z, reflecting the difference in phase voltage amplitude between the trunk line of the distribution area and the installation point of the reactive power compensation device. The reactive power compensation device can raise the local voltage. If the reactive power compensation device performs reactive power compensation, it will not excessively interfere with the voltage level of the trunk line of the distribution area. The voltage consistency of the local power grid where the trunk line of the distribution area is located is high and the fluctuation is low.
[0064] In the actual operation of AC power grid distribution areas, various nonlinear loads are distributed on AC busbars. These loads have complex characteristics and not only consume the active power provided by the line, but also inevitably generate a certain amount of reactive power consumption. Although reactive power is not directly converted into useful working power, it is crucial for maintaining the stable operation of the power grid and supporting the voltage level.
[0065] If the trunk node is within the compensation coverage of the reactive power compensation device, it indicates that the electrical distance between the two is short and the line impedance is small. The reactive current generated by the reactive power compensation device will flow quickly to the trunk node, and the synchronous characteristics of the reactive power change between the trunk node and the compensation point are obvious.
[0066] Based on the above analysis, the synchronicity of reactive power changes between trunk node i and compensation point z is obtained by examining the correlation of reactive power dynamic changes between them. Specifically:
[0067] Based on the changes in reactive power of each phase at trunk node i and compensation point z within a preset time range, obtain the reactive power variation sequence of each phase at trunk node i and compensation point z.
[0068] Calculate the correlation coefficient of the reactive power variation sequence of each phase between trunk node i and compensation point z;
[0069] The reactive power variation synchronization degree is obtained by the correlation coefficient of the three phases between the trunk node i and the compensation point z.
[0070] In this embodiment, the preset time range is the 15 minutes preceding the t-th acquisition time. The process of obtaining the reactive power variation sequence is as follows: within the preset time range, the reactive power of each phase of trunk node i is arranged in time sequence to form the reactive power sequence of each phase of trunk node i. The first-order difference sequence of the reactive power sequence of each phase of trunk node i is used as the reactive power variation sequence of each phase of trunk node i. The reactive power variation sequence of each phase of compensation point z is obtained according to the method for obtaining the reactive power variation sequence of each phase of trunk node i. The first-order difference calculation is a well-known technique and will not be described in detail in this application. The 15 minutes is only one embodiment of this application, and the implementer can set it according to the actual situation. This application does not impose any special restrictions.
[0071] In this embodiment, the correlation coefficient is specifically the Pearson correlation coefficient. The Pearson correlation coefficient is a well-known technology and will not be described in detail in this application. As other implementation methods, based on the ability to measure the correlation between reactive power variation sequences, implementers may use other existing feasible technologies, such as the Spearman correlation coefficient, etc. This application does not impose any special restrictions.
[0072] In this embodiment, the expression for the reactive power variation synchronization degree between trunk node i and compensation point z is:
[0073] In the formula, This indicates the degree of synchronization of reactive power variation between trunk node i and compensation point z. This represents the correlation coefficient of the reactive power variation sequence of each phase between trunk node i and compensation point z. The 1 in the numerator serves to... The mapping is to non-negative values, and the role of 2 in the denominator is to normalize the numerator.
[0074] It should be noted that the main line node and the compensation point are connected to different types of loads with varying sizes, resulting in significant differences in the absolute value of reactive power. Therefore, the reactive power variation sequence, compared to the reactive power sequence, better reflects the reactive power changes between the main line node and the compensation point, which is beneficial for capturing the dynamic coupling relationship between distribution lines in the AC power grid area. In circuit theory, if the main line node i is within the compensation coverage area of the reactive power compensation device at compensation point z, and a disturbance is injected into compensation point z, such as when the reactive power compensation device adjusts its output or when the load fluctuates, the reactive power of the main line node i can respond promptly and change abruptly. The reactive power changes between the main line node i and the compensation point z exhibit high unidirectionality and synchronicity.
[0075] In an AC power grid distribution area, reactive power flows from high voltage points to low voltage points. The flow path is mainly determined by the impedance of the distribution lines. Within the coverage area of the reactive power compensation device, there is a reactive power flow boundary point. At this boundary point, the reactive current from the reactive power compensation device is just consumed, and the subsequent load is mainly compensated by other reactive power compensation devices. In the topology diagram of the AC power grid distribution area, if the shortest connecting line node p and trunk node q does not pass through other trunk nodes, then trunk node p and trunk node q are adjacent nodes. Taking trunk node i as an example, the boundary coefficient of trunk node i is obtained by the reversal characteristics of reactive power flow between trunk node i and its adjacent trunk nodes, specifically:
[0076] Calculate the difference between the elements at the same position in the reactive power sequence of each phase between trunk node i and its adjacent trunk nodes to obtain the deviation sequence of each phase between trunk node i and its adjacent trunk nodes. Calculate the zero-crossing rate of the deviation sequence of each phase between trunk node i and its adjacent trunk nodes. The zero-crossing rate refers to the ratio of the number of sign changes in the deviation sequence to the total number of data.
[0077] The limit coefficient of trunk node i is the maximum value of the zero-crossing rates of the three phases between trunk node i and all its adjacent trunk nodes.
[0078] It should be noted that: the reversal of reactive power flow is the boundary for defining the coverage area of reactive power compensation devices. Within a reactive power compensation sub-region, the reactive power of each trunk node should be of the same polarity. The greater the zero-crossing rate of the deviation sequence, the easier it is for the reactive power flow direction of the trunk node to reverse, and the more likely it is to be the boundary of the reactive power compensation coverage area.
[0079] Furthermore, at the boundary of the reactive power compensation coverage area, due to competition between reactive power sources on both sides, the relative magnitude of reactive power between trunk nodes is easily affected by load fluctuations and alternates, resulting in a significantly higher zero-crossing rate than in the inner region. Based on the above analysis, by using the boundary coefficients of each trunk node, and combining the voltage deviation and reactive power variation synchronicity between each trunk node and each compensation point, the AC power grid area is divided into reactive power compensation coverage sub-areas dominated by each compensation point, specifically:
[0080] The segmentation threshold of the boundary coefficients of all trunk nodes is obtained to help identify the boundary nodes of the reactive power compensation coverage area. By comparing the boundary coefficient of trunk node i with the segmentation threshold, the compensation membership degree of trunk node i relative to compensation point z is calculated according to different cases using the voltage deviation degree between trunk node i and compensation point z, and the reactive power change synchronization degree between trunk node i and compensation point z, reflecting the possibility that trunk node i belongs to the reactive power compensation coverage area of compensation point z.
[0081] By using the compensation membership degree of each trunk node relative to each compensation point, the AC power grid area is divided into various reactive power compensation coverage sub-areas using a fuzzy clustering algorithm.
[0082] The expression for the compensation membership degree of trunk node i relative to compensation point z is:
[0083] In the formula, This represents the compensation membership degree of trunk node i relative to compensation point z; This represents the normalized value of the voltage deviation between trunk node i and compensation point z. This indicates the degree of synchronization of reactive power variation between trunk node i and compensation point z. Represents the limit coefficient of trunk node i; This represents the segmentation threshold for the boundary coefficients of all trunk nodes. The formula for calculating the normalized value of the voltage deviation between trunk node i and compensation point z is: In the formula, Z represents the voltage deviation between trunk node i and compensation point z; Z represents the total number of compensation points within the AC power grid area.
[0084] In this embodiment, the Otsu threshold segmentation algorithm is used to obtain the segmentation threshold of the boundary coefficients of all trunk nodes. The Otsu threshold segmentation algorithm is a well-known technology and will not be described in detail in this application. As other implementation methods, based on the ability to obtain the segmentation threshold of the boundary coefficients of all trunk nodes, the implementer may use other existing feasible technologies, such as global threshold segmentation, iterative threshold segmentation, etc. This application does not impose any special restrictions.
[0085] In this embodiment, a membership matrix is constructed by calculating the compensation membership degree of each trunk node relative to each compensation point. The AC power grid area is divided into multiple reactive power compensation coverage sub-areas using the fuzzy C-means clustering algorithm. The number of clusters in the fuzzy C-means algorithm is consistent with the total number of compensation points.
[0086] It should be noted that: It reflects the difference in voltage amplitude between trunk node i and compensation point z after load weight correction. The larger the value, the weaker the voltage support effect of compensation point z on trunk node i through reactive power compensation. It reflects the consistency of the dynamic fluctuation of reactive power between trunk node i and compensation point z. The larger the value, the more timely the reactive power of the trunk node can respond and jump when the reactive power compensation device adjusts the output or load fluctuation, and the stronger the dynamic coupling of reactive power between trunk node i and compensation point z.
[0087] Summation and normalization is a common data processing method aimed at reducing voltage deviation. The value range is fixed between 0 and 1, which is consistent with the value range of reactive power variation synchronicity.
[0088] In AC power grid areas, accurately identifying the effective coverage area of reactive power compensation devices is crucial for achieving reactive power stratification balance, reducing line losses, and improving voltage quality. Linear summation, a common technique in data processing, requires a boundary coefficient due to the variable reactive power flow direction at the boundary nodes of the effective coverage area of the reactive power compensation device. Introducing the boundary characteristics of the compensation coverage area, reactive power fluctuations are affected by multiple factors. To avoid misjudgment, a static voltage deviation term is introduced to address the low confidence level of the term. Greater weighting increases the "conservatism" of compensation membership, ensuring the stability of the membership relationship of boundary nodes and preventing multiple reactive power compensation devices from making reverse adjustments to the same trunk node, thereby improving the overall voltage quality.
[0089] Step 3: Calculate the line loss of each transformer trunk line within each reactive power compensation coverage sub-area, and use a prediction model to analyze and predict the historical line loss at multiple time scales to obtain multi-time scale prediction information; by comparing the estimated line loss at the instantaneous time scale in the multi-time scale prediction information with the overall prediction level, obtain the compensation parameters of the reactive power compensation device within each reactive power compensation coverage sub-area, and then correct the compensation capacity of the reactive power compensation device to dynamically compensate the distribution lines.
[0090] Reactive power is crucial for maintaining stable grid operation and supporting voltage levels. By installing reactive power compensation devices in AC grid distribution areas, reactive power in the system can be dynamically adjusted and compensated according to the actual needs of the grid, thereby reducing the flow and loss of reactive power in the grid and achieving energy saving and loss reduction in power distribution lines.
[0091] After the AC power grid area is divided into multiple reactive power compensation coverage sub-areas, in order to improve the compensation effect of the reactive power compensation device, it is necessary to calculate the line loss of each reactive power compensation coverage sub-area. For any trunk node p, trunk node q is an adjacent node of trunk node p. The trunk line between trunk node p and trunk node q is denoted as ... Main line of the substation The expression for line loss is:
[0092] In the formula, Indicates the main line of the substation Line loss; Indicates the main line of the substation The predicted phase current of phase x is specifically the average of the phase currents of phase x at trunk node p and phase x at trunk node q. Indicates the main line of the substation The resistance is specifically the product of the unit resistance of the main line in the distribution area and the line length. For example, the unit resistance of the LGJ-50 distribution line is generally 0.64Ω / km.
[0093] The predictive model is used to analyze and predict historical line losses at multiple time scales to obtain multi-time scale forecast information, specifically:
[0094] Since the sampling frequency of the metering acquisition device is 50Hz, in this embodiment, the multi-time scale levels are set to 0.02s, 0.1s, 0.2s, 0.5s, and 1s, respectively, where 0.02s is the instantaneous time scale, for calculating the trunk line of the distribution area. The average line loss over various time scales is used as the trunk line of the distribution area. Historical loss data at various time scales. For example, calculating the trunk line of the distribution area. The average line loss value within 0.1s is used as the trunk line of the transformer area. Historical loss data on a 0.1s timescale;
[0095] A multi-time-scale loss prediction method for low-voltage distribution transformer substations based on least squares support vector machines is adopted. The historical loss data of the trunk lines of each substation substation at multiple time scales are used as input to obtain the loss prediction value of the trunk lines of each substation substation at each time scale. This indicates the main power line of the transformer sub-area within the reactive power compensation coverage sub-area where compensation point z is located. Loss estimates at time scale t;
[0096] Calculate the cumulative value of the estimated loss of all transformer trunk lines within each reactive power compensation coverage sub-area at each time scale. This sum is used as the estimated sub-area line loss for each reactive power compensation coverage sub-area at each time scale. These values are then arranged in ascending order of time scale hierarchy to form a multi-time scale sub-area line loss sequence. This refers to multi-timescale prediction information. Among them, the multi-timescale loss prediction method for low-voltage distribution substations based on least squares support vector machines is a well-known technique and will not be described in detail in this application.
[0097] Furthermore, by comparing the estimated line loss at the instantaneous time scale with the overall estimated level in the multi-time-scale forecast information, the compensation parameters of the reactive power compensation devices in each reactive power compensation coverage sub-area are corrected, thereby correcting the compensation capacity of the reactive power compensation devices in each reactive power compensation coverage sub-area, specifically as follows:
[0098] Calculate the average value of the sub-region line loss estimate for each reactive power compensation coverage sub-region across all time scales;
[0099] The ratio of the average value to the estimated line loss of each reactive power compensation coverage sub-region on an instantaneous time scale is denoted as the parameter compensation coefficient; the compensation parameters of the reactive power compensation device in each reactive power compensation coverage sub-region are positively correlated with the parameter compensation coefficient.
[0100] The product of the compensation parameter and the estimated sub-region line loss of each reactive power compensation coverage sub-region at the instantaneous time scale is denoted as the capacity correction amount.
[0101] The sum of the preset compensation capacity benchmark value of the reactive power compensation device in each reactive power compensation coverage sub-area and the capacity correction amount is used as the correction value of the compensation capacity of the reactive power compensation device in each reactive power compensation coverage sub-area.
[0102] It should be noted that positive correlation means that the independent variables change in the same direction; when one variable increases, the other variable also increases, and when one variable decreases, the other variable also decreases.
[0103] In this embodiment, the expression for correcting the compensation parameter using the compensation coefficient is as follows:
[0104] In the formula, This represents the compensation parameters of the reactive power compensation device within the reactive power compensation coverage sub-region where compensation point z is located. This indicates the preset compensation parameter reference value of the reactive power compensation device; The adjustment factor represents the compensation parameter, which is used to control the sensitivity of dynamic adjustment, avoid drastic changes in the compensation parameter due to instantaneous data disturbances, and ensure the smoothness of the dynamic adjustment mechanism. The value range is [0.1, 1], and the value in this embodiment is 0.2. This represents the mean of the estimated line loss values for all sub-regions within the sub-region line loss sequence of the reactive power compensation coverage sub-region where compensation point z is located; This represents the estimated line loss of the first sub-region in the sub-region line loss sequence of the reactive power compensation coverage sub-region where compensation point z is located, i.e., the estimated line loss of the sub-region at a time scale of 0.02s. It is denoted as the parameter compensation coefficient.
[0105] In this embodiment, the expression for the compensation capacity of the reactive power compensation device within each reactive power compensation coverage sub-area is modified as follows:
[0106] In the formula, This represents the correction value for the compensation capacity of the reactive power compensation device within the reactive power compensation coverage sub-region where compensation point z is located; This represents the preset initial value of the compensation capacity of the reactive power compensation device within the reactive power compensation coverage sub-area where compensation point z is located; This represents the correction value of the compensation parameters of the reactive power compensation device within the reactive power compensation coverage sub-region where compensation point z is located; This represents the estimated line loss of the first sub-region in the sub-region line loss sequence within the reactive power compensation coverage sub-region where compensation point z is located. This is denoted as the capacity correction amount.
[0107] In this embodiment, the preset compensation parameter baseline value is 0.5, and the preset initial value of the compensation capacity is 100Kvar. Both the preset compensation parameter baseline value and the preset initial value of the compensation capacity are obtained through experimental calculation.
[0108] It should be noted that the estimated sub-region line loss on the instantaneous time scale is considered as the response demand of the reactive power compensation coverage sub-region to the instantaneous reactive power deficit, and is determined through... Introduce a dynamic adjustment mechanism, when This indicates that the line loss in the reactive power compensation covered sub-area is very likely to show an increasing trend. Increase the reactive power compensation level appropriately to maintain voltage stability; conversely, when... If this is the case, the line loss in the reactive power compensation coverage area is very likely to decrease. The compensation intensity should be appropriately reduced to prevent voltage over-adjustment or oscillation.
[0109] Obtain the correction value of the compensation capacity of the reactive power compensation device in the reactive power compensation coverage sub-area where each compensation point is located in the AC power grid distribution area, adjust the output of the reactive power compensation device in real time, ensure that the voltage of the reactive power compensation coverage sub-area is stable within a reasonable range, reduce the quasi-steady-state voltage deviation of the AC power grid distribution area, and avoid additional line losses caused by excessively high or low voltage.
[0110] In summary, this application introduces active power distribution weights to enable voltage deviation to adaptively reflect the actual load distribution, giving greater attention to heavily loaded phases; by calculating reactive power variation synchronicity, it can effectively capture the dynamic coupling characteristics between distribution lines; considering that at the reactive power flow boundary point, the reactive power polarity of adjacent trunk nodes is easily reversed, and the zero-crossing rate is significantly higher than in the internal area, obtaining the boundary coefficient can accurately identify the compensation coverage boundary, enhance the "conservatism" of boundary node compensation judgment, avoid multiple reactive power sources from reversely adjusting the same node, realize dynamic zonal compensation, and effectively prevent voltage fluctuations;
[0111] Furthermore, the instantaneous time scale reflects the immediate reactive power deficit, while the long-term time scale reflects the trend change, taking into account both rapid response and stability. By predicting line losses, it can predict the trend of line loss changes in advance and dynamically adjust the compensation capacity of the reactive power compensation device. It can proactively adjust the compensation output before voltage fluctuations, avoid voltage over-adjustment or oscillation, and reduce the long-distance flow of reactive power on the trunk line by distributing compensation through the reactive power compensation device, thereby reducing active power loss and voltage drop and improving the overall power quality.
[0112] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to embodiments of this disclosure. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. In some alternative implementations, the functions marked in the blocks may occur in a different order than that shown in the drawings. For example, two consecutive blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. In the descriptions corresponding to the flowcharts and block diagrams in the accompanying drawings, the operations or steps corresponding to different blocks may also occur in a different order than disclosed in the description, and sometimes there is no specific order between different operations or steps. For example, two consecutive operations or steps may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. Each block in a block diagram and / or flowchart, and combinations of blocks in a block diagram and / or flowchart, can be implemented using a dedicated hardware-based system that performs the specified function or action, or using a combination of dedicated hardware and computer instructions.
[0113] It will be apparent to those skilled in the art that this application is not limited to the details of the exemplary embodiments described above, and that this application can be implemented in other specific forms without departing from its essential characteristics. Therefore, the embodiments described above should be considered exemplary and non-limiting in all respects.
Claims
1. A method for dynamic compensation and adjustment of power distribution lines to prevent voltage fluctuations, characterized in that, The method includes the following steps: At each moment, the voltage deviation between each trunk node and each compensation point is obtained by analyzing the distribution of three-phase active power at each trunk node and the phase voltage differences between each trunk node and each compensation point in the AC power grid area. The reactive power dynamic change synchronicity between each trunk node and each compensation point is obtained by analyzing the correlation between the dynamic changes of reactive power. The boundary coefficient of each trunk node is obtained by analyzing the reversal characteristics of reactive power flow between each trunk node and its adjacent trunk nodes. These factors are then combined with the voltage deviation and the reactive power... The reactive power compensation synchronization degree divides the AC power grid into reactive power compensation coverage sub-areas dominated by each compensation point; the line loss of each distribution trunk line in each reactive power compensation coverage sub-area is calculated, and the historical line loss at multiple time scales is analyzed and predicted using a prediction model to obtain multi-time scale prediction information; by comparing the estimated line loss at the instantaneous time scale in the multi-time scale prediction information with the overall prediction level, the compensation parameters of the reactive power compensation device in each reactive power compensation coverage sub-area are obtained, and then the compensation capacity of the reactive power compensation device is corrected to dynamically compensate the distribution lines; The process of obtaining the reactive power variation synchronization degree is as follows: Based on the changes in reactive power of each phase at each trunk node and each compensation point within a preset time range, obtain the reactive power variation sequence of each phase at each trunk node and each compensation point. Calculate the correlation coefficient of the reactive power variation sequence of each phase between each trunk node and each compensation point; The reactive power variation synchronization degree is obtained by the correlation coefficient of the three phases between each trunk node and each compensation point; The process of obtaining the boundary coefficient is as follows: The reactive power of each phase of each trunk node within a preset time range is arranged in time sequence to form the reactive power sequence of each phase of each trunk node. The difference of the elements at the same position in the reactive power sequence of each phase between each trunk node and its adjacent trunk nodes is calculated to obtain the deviation sequence of each phase between each trunk node and its adjacent trunk nodes. The zero-crossing rate of the deviation sequence of each phase between each trunk node and its adjacent trunk nodes is calculated. The limit coefficient is the maximum value of the zero-crossing rates of the three phases between each trunk node and all its adjacent trunk nodes. The process of dividing the reactive power compensation coverage sub-region is as follows: Obtain the segmentation threshold of the boundary coefficients of all trunk nodes; by comparing the boundary coefficients of each trunk node with the segmentation threshold, calculate the compensation membership degree of each trunk node relative to each compensation point by using the voltage deviation degree and the reactive power variation synchronization degree in different cases. Based on the aforementioned compensation membership degree, a fuzzy clustering algorithm is used to divide the AC power grid area into various reactive power compensation coverage sub-regions.
2. The method for dynamic compensation and adjustment of power distribution lines to prevent voltage fluctuations as described in claim 1, characterized in that, The process of obtaining the voltage deviation is as follows: Calculate the difference in phase voltage between each main line node and each compensation point; The ratio of the active power of each phase at each trunk node to the active power of the three phases is denoted as the power ratio. The voltage deviation is positively correlated with all the power ratios corresponding to each trunk node, and is also positively correlated with the difference.
3. The method for dynamic compensation and adjustment of power distribution lines to prevent voltage fluctuations as described in claim 2, characterized in that, The calculation process for the voltage deviation is as follows: The difference between the highest and lowest allowable voltages of the main line in the distribution area is recorded as the allowable voltage variation, and the ratio of the difference to the allowable voltage variation is recorded as the absolute voltage deviation. Calculate the product of the power ratio of each phase at each trunk node and the absolute voltage deviation. The voltage deviation is the sum of the products of the three phases at each trunk node.
4. The method for dynamic compensation and adjustment of power distribution lines to prevent voltage fluctuations as described in claim 1, characterized in that, The calculation process for the compensated membership degree is as follows: Calculate the difference between 1 and the normalized value of the voltage deviation; use the weighted sum of the difference and the reactive power variation synchronicity as the compensation membership degree; wherein, when the limit coefficient of each trunk node is less than the segmentation threshold, the weights of the difference and the reactive power variation synchronicity are both 1; otherwise, the weight of the difference is the sum of 1 and the limit coefficient, and the weight of the reactive power variation synchronicity is the difference between 1 and the limit coefficient.
5. The method for dynamic compensation and adjustment of power distribution lines to prevent voltage fluctuations as described in claim 1, characterized in that, The process of obtaining the multi-time-scale prediction information is as follows: the average line loss of each transformer area trunk line at multiple time scales, including preset instantaneous time scales and preset long-term time scales, is predicted in a rolling manner. The sum of the average line loss of all transformer area trunk lines in each reactive power compensation coverage sub-area at each time scale is used as the sub-area line loss prediction value of each reactive power compensation coverage sub-area at each time scale.
6. The method for dynamic compensation and adjustment of power distribution lines to prevent voltage fluctuations as described in claim 5, characterized in that, The process of obtaining the compensation parameters is as follows: Calculate the average value of the sub-region line loss estimate for each reactive power compensation coverage sub-region across all time scales; The ratio of the average value to the estimated line loss of each reactive power compensation coverage sub-region at the instantaneous time scale is denoted as the parameter compensation coefficient; the compensation parameter and the parameter compensation coefficient are positively correlated.
7. The method for dynamic compensation and adjustment of power distribution lines to prevent voltage fluctuations as described in claim 6, characterized in that, The correction process for the compensation capacity is as follows: The product of the compensation parameter and the estimated sub-region line loss of each reactive power compensation coverage sub-region at the instantaneous time scale is denoted as the capacity correction amount. The correction value of the compensation capacity is the sum of the preset initial value of the compensation capacity of the reactive power compensation device and the capacity correction amount.