Load distribution estimation device, load distribution estimation method, and load distribution estimation program

Abstract

To provide a load distribution estimation device, a load distribution estimation method, and a load distribution estimation program for appropriately estimating a load distribution under an environment in which SVR is arranged.SOLUTION: A pre-processing unit 101 acquires, from each of two distribution line sensors arranged in a distribution line, information on an effective power flow and an ineffective power flow at their positions, and generates a power flow model in which a difference in effective power flow and a difference in ineffective power flow are distributed equivalently between the distribution line sensors. A voltage estimation unit 102 executes power flow calculation based on the power flow model to obtain an estimated value of a voltage at a position of one of the distribution line sensors. A tap position determination unit 103 determines a tap position of an automatic voltage regulator for power distribution arranged between the distribution line sensors based on a difference between a measured value of a voltage by one of the distribution line sensors and the estimated value. A load distribution estimation unit 11 estimates a load distribution between the distribution line sensors based on the tap position determined by the tap position determination unit 103, as well as the information on the effective power flow and the ineffective power flow at the position of each of the distribution line sensors.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a load distribution estimation device, a load distribution estimation method, and a load distribution estimation program.

Background Art

[0002] In recent years, in the power distribution system, due to the influence of the large-scale introduction of renewable energy power sources (renewable energy power), it has become difficult to maintain power quality. Specifically, short-period voltage fluctuations due to output fluctuations of renewable energy power sources, high-frequency faults, etc. have occurred, and early suppression measures have become important. In addition, due to the increase in renewable energy power sources, the short-circuit capacity of the power distribution system has increased, and changes in the connection positions of renewable energy power sources and equipment countermeasures are required.

[0003] On the other hand, in the management of the power distribution system by general power distribution operators, heretofore, equipment planning, operation planning, and control have been performed by evaluating the static characteristics by cutting out a time cross-section. However, it is difficult to consider the control of renewable energy power sources and the behavior during accidents in the evaluation of the static characteristics by cutting out a time cross-section. Therefore, it is difficult to consider countermeasures for short-period voltage fluctuations, harmonic faults, and short-circuit capacity in the management of the power distribution system by general power distribution operators.

[0004] Based on such a situation, the development and improvement of a power distribution system analysis tool for performing dedicated analysis of the power distribution system for considering countermeasures for short-period voltage fluctuations, harmonic faults, and short-circuit capacity have been promoted. However, although the speed of the power distribution system analysis tool has been improved, the most time-consuming and labor-intensive part when using it is data input. When the analysis target is a large-scale system, it is difficult for users to input all the data. Therefore, a system for automating the input of equipment data such as power distribution equipment data, customer data, and distributed power source data, and contract data has been developed.

[0005] On the other hand, unlike fixed information such as equipment data and contract data, it has been difficult to automate the input of time-varying data such as the power consumption data of each customer and the power output data of each customer's distributed power sources. To enable the automation of inputting time-varying data such as the power consumption data of each customer and the power output data of each operator's distributed power sources, it is conceivable to utilize the measurement data from sensor-equipped switches installed by general transmission and distribution companies to observe voltage and power flow. Currently, the elements of measurement data from general transmission and distribution companies are voltage, active power flow, and reactive power flow, which are measured at intervals of 10 to 30 minutes and stored on a server. However, there are several problems in directly utilizing the measurement data from general transmission and distribution companies for analysis.

[0006] One of the problems is that the measured active and reactive power flows represent the power flow for the entire area measured by the sensor-integrated switch, and it is not possible to know where they are distributed within that area. While it is possible to determine the distribution of active and reactive power flows by apportioning them according to the capacity ratio of the customer's contracted power and the rated output of the operator's distributed power sources, in reality, power is not consumed according to the contracted power, nor is power generated according to the rated output of the distributed power sources, so an accurate distribution is not represented. Therefore, even if voltage analysis is performed using this distribution, the voltage measured by the sensor-integrated switch and the voltage calculated will almost always not match. In the field of general power transmission and distribution companies, when the measured values ​​and analyzed values ​​do not match, it is often judged as a calculation error of the analysis tool, but this is incorrect, and in reality, it can be considered that the input values ​​do not match the actual situation.

[0007] Therefore, as a technology to solve this problem, a technique has been proposed that automatically determines the load distribution so that the measurement data from two sensor-equipped switches on either side of the section where the load distribution needs to be estimated matches. The location and amount of load points obtained by this method are only set virtually, but it has the significant advantage that the actual state of the power distribution line can be estimated from sensor information and modeled on an analysis tool.

[0008] Furthermore, the following techniques have been proposed for estimating load distribution in power distribution systems. For example, there is a technique that calculates the average actual load at each load connection point, calculates the actual load at the time of estimation from the amount of PV power generation and the measured power, allocates it by the average actual load to find the actual load, and then estimates the load at each load connection point by subtracting the amount of PV power generation from the calculated actual load. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Japanese Patent Publication No. 2013-162666 [Non-patent literature]

[0010] [Non-Patent Document 1] Tanaka and Uemura, "A Method for Estimating Voltage in Power Distribution Systems Based on Sensor Switch Information," Central Research Institute of Electric Power Industry Report, R04011, 2005. [Overview of the project] [Problems that the invention aims to solve]

[0011] However, conventional load distribution estimation techniques may struggle to estimate the load distribution if a Step Voltage Regulator (SVR) is installed between sensor-integrated switches. Furthermore, if the load distribution is forcibly estimated, the voltage and power flow at the sensor-integrated switches may not match. This is because many SVRs lack communication capabilities, making it difficult to remotely determine tap positions and thus difficult to understand the extent of voltage regulation performed by the SVR. Therefore, conventional load distribution estimation techniques struggle to accurately estimate the load distribution in environments where SVRs are present, leading to a decrease in the accuracy of power distribution system analysis tools and making it difficult to maintain power quality.

[0012] Furthermore, in techniques that estimate the load at each load connection point based on the actual load obtained by calculating the actual load at the time of estimation from the amount of power generated and the measured power, and then apportioning it by the average actual load, voltage adjustment by SVR is not taken into consideration, making it difficult to estimate an appropriate load distribution.

[0013] The disclosed technology was made in view of the above, and aims to provide a load distribution estimation device, a load distribution estimation method, and a load distribution estimation program that appropriately estimate the load distribution in an environment in which an SVR is installed. [Means for solving the problem]

[0014] In one embodiment of the load distribution estimation device, load distribution estimation method, and load distribution estimation program disclosed herein, a preprocessing unit acquires information on effective and ineffective power flow at each location from each of two power distribution line sensors arranged on a power distribution line, and generates a power flow model in which the difference in effective power flow and the difference in ineffective power flow are evenly distributed between the power distribution line sensors. A voltage estimation unit performs a power flow calculation based on the power flow model generated by the preprocessing unit to obtain an estimated voltage at the location of one of the power distribution line sensors. A tap position determination unit acquires a measured voltage from one of the power distribution line sensors and determines the tap position of an automatic voltage regulator for power distribution arranged between the power distribution line sensors based on the difference between the measured voltage and the estimated voltage. A load distribution estimation unit estimates the load distribution between the power distribution line sensors based on the tap position determined by the tap position determination unit, and the information on effective and ineffective power flow at each location of the two power distribution line sensors. [Effects of the Invention]

[0015] In one respect, the present invention can appropriately estimate the load distribution in an environment in which an SVR is installed. [Brief explanation of the drawing]

[0016] [Figure 1] Figure 1 is a block diagram of a load distribution estimation device according to an embodiment. [Figure 2]FIG. 2 is a schematic diagram of a distribution line for which load distribution is to be estimated. [Figure 3] FIG. 3 is a diagram for explaining the uniform distribution of the difference in active power flow and the difference in reactive power flow. [Figure 4] FIG. 4 is a diagram showing the relationship between the tap width of the SVR and the voltage difference. [Figure 5] FIG. 5 is a diagram for explaining the estimation process of the tap position. [Figure 6] FIG. 6 is a diagram for explaining the estimation result of the load distribution. [Figure 7] FIG. 7 is a flowchart of the load distribution estimation process by the load distribution estimation device according to the embodiment. [Figure 8] FIG. 8 is a diagram summarizing the estimation results by the load distribution estimation device according to the embodiment. [Figure 9] FIG. 9 is a diagram showing the evaluation result of the interval of the sensor - incorporated switch that enables accurate estimation. [Figure 10] FIG. 10 is a hardware configuration diagram of the load distribution estimation device.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, embodiments of the load distribution estimation device, load distribution estimation method, and load distribution estimation program disclosed in the present application will be described in detail based on the drawings. Note that the load distribution estimation device, load distribution estimation method, and load distribution estimation program disclosed in the present application are not limited by the following embodiments.

Embodiment

[0018] FIG. 1 is a block diagram of the load distribution estimation device according to the embodiment. The load distribution estimation device 1 according to this embodiment is connected to the sensor - incorporated switch 20.

[0019] The sensor-integrated switch 20 is placed on the power distribution line that is the target of load distribution estimation by the load distribution estimation device 1. The sensor-integrated switch 20 measures the voltage, effective power flow, and reactive power flow at the location where it is placed. However, the sensor-integrated switch 20 may also measure the voltage, current, and power factor at the location where it is placed. In that case, the effective power flow and reactive power flow can be calculated from the measurement data acquired by the sensor-integrated switch 20.

[0020] As shown in Figure 1, the load distribution estimation device 1 includes a tap position estimation unit 10 and a load distribution estimation unit 11. Furthermore, the tap position estimation unit 10 includes a preprocessing unit 101, a voltage estimation unit 102, and a tap position determination unit 103.

[0021] The preprocessing unit 101 acquires measurement data of effective and ineffective currents from the two sensor-integrated switches 20. Then, the preprocessing unit 101 performs preprocessing for tap position estimation using the acquired measurement data of effective and ineffective currents. The details of the processing performed by the preprocessing unit 101 are described below.

[0022] Figure 2 is a schematic diagram of the distribution line for which the load distribution is to be estimated. Distribution line 3 supplies power output from substation 4 to each load. For example, two sensor-integrated switches 20 are arranged on distribution line 3. Here, the distribution line sensor that measures voltage, active power flow and reactive power flow, held by the sensor-integrated switch 20 closer to substation 4, is referred to as the upstream distribution line sensor 21. The distribution line sensor held by the sensor-integrated switch 20 further from substation 4 is referred to as the downstream distribution line sensor 22. Figure 2 illustrates the upstream distribution line sensor 21 and the downstream distribution line sensor 22 held by the sensor-integrated switch 20. An SVR 30 is also placed between the two sensor-integrated switches 20 on distribution line 3. Here, the line constant between the upstream distribution line sensor 21 and the downstream distribution line sensor 22 on distribution line 3 is R + jX. This R+jX represents the impedance of the distribution line 3 in this section. The shorter the distance between the upstream distribution line sensor 21 and the downstream distribution line sensor 22, the smaller the impedance. And the smaller the impedance, the smaller the voltage change due to changes in load distribution, which leads to a larger estimation error.

[0023] In this embodiment, the pre-processing unit 101 acquires V1 as the voltage measurement value, P1 as the effective power flow measurement value, and Q1 as the reactive power flow measurement value from the upstream power distribution line sensor 21. The pre-processing unit 101 also acquires V2 as the voltage measurement value, P2 as the effective power flow measurement value, and Q2 as the reactive power flow measurement value from the downstream power distribution line sensor 22.

[0024] Next, the pre-processing unit 101 calculates the difference between the effective power flow measured by the upstream power distribution line sensor 21 and the effective power flow measured by the downstream power distribution line sensor 21. Here, if the difference in effective power flow is denoted as PL, the pre-processing unit 101 calculates the difference in effective power flow as PL = P1 - P2.

[0025] Furthermore, the pre-processing unit 101 calculates the difference between the measured value of the reactive power flow measured by the upstream power distribution line sensor 21 and the measured value of the reactive power flow measured by the downstream power distribution line sensor 21. Here, if the difference in effective power flow is QL, the pre-processing unit 101 calculates the difference in reactive power flow as QL = Q1 - Q2.

[0026] Next, the pre-processing unit 101 assumes that the SVR30 is not installed and distributes the difference in effective power flow and the difference in ineffective power flow evenly between the sensors. Here, "between sensors" refers to the space between the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22. Figure 3 is a diagram illustrating the even distribution of the difference in effective power flow and the difference in ineffective power flow. As an example, when distributing the difference in effective power flow and the difference in ineffective power flow evenly to three locations between the sensors, the pre-processing unit 101 calculates one-third of both the difference in effective power flow and the difference in ineffective power flow. Here, if the difference in effective power flow is PL and the difference in ineffective power flow is QL, the pre-processing unit 101 calculates PL / 3 and QL / 3. The pre-processing unit 101 then assumes that the effective power flow decreases by PL / 3 and the ineffective power flow decreases by QL / 3 at the first, third, and fifth positions 201-203, which are the six equal divisions of the path between the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22. Here, six equal divisions refer to dividing the path into six sections: from the upstream power distribution line sensor 21 to position 201, from position 201 to the midpoint between position 201 and position 202, from the midpoint between position 201 and position 202 to position 202, from position 202 to the midpoint between position 202 and position 203, from the midpoint between position 202 and position 203 to position 203, and from position 203 to the downstream power distribution line sensor 22.

[0027] Subsequently, the pre-processing unit 101 outputs information on the effective and ineffective power flow, which are evenly distributed among the sensors, to the voltage estimation unit 102. The pre-processing unit 101 also outputs information on V1, which is the voltage measured by the upstream power distribution line sensor 21, and V2, which is the voltage measured by the downstream power distribution line sensor 22, to the voltage estimation unit 102.

[0028] In this embodiment, we have described the case where the distribution is divided into three positions, but the number of division positions is not limited to this and is not particularly restricted. For example, there may be 10 division positions, and a larger number of division positions may allow for a wider distance between the upstream distribution line sensor 21 and the downstream distribution line sensor 22. However, the more division positions there are, the more complicated the power flow calculation by the voltage estimation unit 102 becomes, so it is preferable to determine the number of division positions based on the required distance between sensors and the allowable load range determined by the power flow calculation.

[0029] The voltage estimation unit 102 receives information on effective and ineffective power flow, evenly distributed between sensors, from the preprocessing unit 101. The voltage estimation unit 102 also receives information on V1, the voltage measured by the upstream power distribution line sensor 21, and V2, the voltage measured by the downstream power distribution line sensor 22, from the preprocessing unit 101. Next, the voltage estimation unit 102 performs power flow calculations to calculate the estimated voltage at the location of the downstream power distribution line sensor 22 when the SVR 30 is not present.

[0030] For example, as shown in Figure 3, if the difference between the active power flow and the reactive power flow is evenly distributed across positions 201 to 203, the voltage estimation unit 102 estimates that the voltage changes linearly in a graph where the vertical axis represents voltage and the horizontal axis represents position. That is, the voltage estimation unit 102 estimates that the change in voltage is represented by a linear function 233 that passes through point 211, which represents the position of the upstream power distribution line sensor 21 and the measured voltage V1, and where the active power and reactive power decrease by PL / 3 and QL / 3 respectively at positions 201 to 203. The voltage estimation unit 102 then determines the voltage corresponding to the position of the downstream power distribution line sensor 22 in the linear function 233 as the estimated voltage V2min.

[0031] Subsequently, the voltage estimation unit 102 outputs the calculated estimated voltage, V2min, to the tap position determination unit 103. The voltage estimation unit 102 also outputs the voltage measurement value V2 from the downstream power distribution line sensor 22 to the tap position determination unit 103.

[0032] The tap position determination unit 103 receives information about the estimated voltage, V2min, from the voltage estimation unit 102. The tap position determination unit 103 also receives information about the voltage measured by the downstream power distribution line sensor 22, V2, from the voltage estimation unit 102. The tap position determination unit 103 then calculates ΔV, which is the difference between the measured voltage V2 from the downstream power distribution line sensor 22 and the estimated voltage V2min. In other words, the tap position determination unit 103 calculates ΔV = V2 - V2min.

[0033] Figure 4 is a diagram showing the relationship between the tap width of the SVR and the voltage difference. The tap position determination unit 103 pre-stores information representing the relationship between the tap width of the SVR30 and the voltage difference, for example, as shown in Figure 4. Figure 4 is an example of the correspondence between the tap width of the SVR30 and the voltage difference in a device where the SVR30 performs a three-stage switching operation. In Figure 4, Vsvr represents the tap width of the SVR30.

[0034] The tap position determination unit 103 then checks which category the difference ΔV, which is the difference between V2 (the voltage measured by the downstream power distribution line sensor 22) and V2min (the estimated voltage), belongs to, and estimates the tap position of the SVR 30.

[0035] Figure 5 is a diagram illustrating the tap position estimation process. For example, as shown in Figure 5, the explanation will be given when ΔV, which is the difference between V2, the voltage measured by the downstream power distribution line sensor 22, and V2min, the estimated voltage, is 2Vsvr. In this case, the tap position determination unit 103 estimates the position of SVR30 to be two stages, since 1.5Vsvr ≤ ΔV < 2.5Vsvr.

[0036] Subsequently, the tap position determination unit 103 outputs the estimated tap position information of the SVR30 to the load distribution estimation unit 11.

[0037] The load distribution estimation unit 11 receives information about the estimated tap positions of the SVR 30 as input from the tap position determination unit 103. The load distribution estimation unit 11 fixes the estimated tap positions of the SVR 30 and performs load distribution estimation.

[0038] Specifically, the load distribution estimation unit 11 receives information on voltage, active power flow, and reactive power flow at each location from the sensor-integrated switch 20 which houses the upstream power distribution line sensor 21 and the sensor-integrated switch 20 which holds the downstream power distribution line sensor 22. Next, the load distribution estimation unit 11 calculates the difference between the active power measured by the upstream power distribution line sensor 21 and the active power measured by the downstream power distribution line sensor 22. The load distribution estimation unit 11 also calculates the difference between the reactive power measured by the upstream power distribution line sensor 21 and the reactive power measured by the downstream power distribution line sensor 22.

[0039] Next, the load distribution estimation unit 11 assumes that the differences obtained at three virtual load points, which are division points that equally divide the path between the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22, are evenly distributed. However, the load distribution estimation unit 11 may obtain information on the differences and information on the case where the differences are evenly distributed from the preprocessing unit 101.

[0040] Next, the load distribution estimation unit 11 fixes the effective and reactive power flow values ​​measured by the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22, and performs power flow calculations with the estimated tap positions of the SVR 30 fixed. The load distribution estimation unit 11 adjusts the load position and load amount so that the effective and reactive power flow obtained from the power flow calculations match the effective and reactive power flow at the respective positions of the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22. Then, the load distribution estimation unit 11 estimates the load distribution in which the voltage at the position of the downstream power distribution line sensor 22 obtained from the power flow calculations matches the voltage measured by the downstream power distribution line sensor 22.

[0041] Specifically, the load distribution estimation unit 11 maintains multiple patterns in which the load is gradually shifted from an evenly distributed state towards the upstream power distribution line sensor 21, and multiple patterns in which the load is gradually shifted towards the downstream power distribution line sensor 22. The load distribution estimation unit 11 then estimates the negative load distribution by switching between these patterns.

[0042] For example, if the voltage at the location of the downstream distribution line sensor 22, determined by power flow calculation, is smaller than the voltage measured by the downstream distribution line sensor 22, the load distribution estimation unit 11 switches the load distribution pattern to gradually shift the load towards the upstream distribution line sensor 21. Conversely, if the voltage at the location of the downstream distribution line sensor 22, determined by power flow calculation, is larger than the voltage measured by the downstream distribution line sensor 22, the load distribution estimation unit 11 switches the load distribution pattern to gradually shift the load towards the downstream distribution line sensor 22. After switching the patterns, when the relative magnitudes of the voltage at the location of the downstream distribution line sensor 22, determined by power flow calculation, and the voltage measured by the downstream distribution line sensor 22 are reversed, the load distribution estimation unit 11 stops switching the patterns. Then, the load distribution estimation unit 11 uses the result of combining the load distribution of the reversed pattern and the load distribution of the previous switching pattern using the ratio of the voltage difference as the estimated load distribution result.

[0043] Figure 6 is a diagram illustrating the load distribution estimation results. The load distribution estimation unit 11 estimates the load distribution such that, for example, the effective flow at position 221 is PLA and the ineffective flow is QLA, the effective flow at position 222 is PLB and the ineffective flow is QLB, and the effective flow at position 223 is PLC and the ineffective flow is QLC.

[0044] The load distribution estimation unit 11 displays the load distribution estimation results on a display device and notifies the operator performing the distribution system analysis using the distribution system analysis tool of the load distribution estimation results. Alternatively, the load distribution estimation unit 11 may input the load distribution estimation results information to the analysis device that runs the distribution system analysis tool.

[0045] Figure 7 is a flowchart of the load distribution estimation process by the load distribution estimation device according to the embodiment. Next, referring to Figure 7, the flow of the load distribution estimation process by the load distribution estimation device 1 according to the embodiment will be explained.

[0046] The pre-processing unit 101 receives active power and reactive power from the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22. The pre-processing unit 101 then calculates the difference between active power and reactive power between the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22 under the condition that the SVR 30 is not installed (step S1).

[0047] Next, the preprocessing unit 101 calculates the active power and reactive power at each division point when the calculated difference is evenly distributed between the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22 (step S2). After that, the preprocessing unit 101 outputs the information when the difference between the active power and reactive power is evenly distributed between the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22 to the voltage estimation unit 102.

[0048] The voltage estimation unit 102 receives information from the preprocessing unit 101 regarding the distribution of the difference between active and reactive power evenly between the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22. The voltage estimation unit 102 then performs a power flow calculation to determine the estimated voltage at the location of the downstream power distribution line sensor 22 (step S3). Subsequently, the voltage estimation unit 102 outputs the information of the estimated voltage at the location of the downstream power distribution line sensor 22 to the tap position determination unit 103.

[0049] The tap position determination unit 103 receives information on the estimated voltage at the position of the downstream power distribution line sensor 22 from the voltage estimation unit 102. Next, the tap position determination unit 103 calculates the difference between the measured voltage from the downstream power distribution line sensor 22 and the estimated voltage (step S4).

[0050] Next, the tap position determination unit 103 estimates the tap position of the SVR30 based on the relationship between the difference between the voltage measured by the downstream power distribution line sensor 22 and the estimated voltage, and the tap width of the SVR30 (step S5). After that, the tap position determination unit 103 outputs the estimated tap position information of the SVR30 to the load distribution estimation unit 11.

[0051] The load distribution estimation unit 11 acquires information on the tap positions of the SVR 30 estimated by the tap position determination unit 103. Then, the load distribution estimation unit 11 sets the estimated tap positions of the SVR 30 and repeatedly performs power flow calculations to estimate the load distribution between the upstream power distribution line sensor 21 and the downstream power distribution line sensor 22 (step S6).

[0052] In this embodiment, the tap position of the SVR30 was estimated using the estimated and measured voltage values ​​at the location of the downstream power distribution line sensor 22. However, conversely, the tap position of the SVR30 may be estimated using the estimated and measured voltage values ​​at the location of the upstream power distribution line sensor 21.

[0053] Next, we will explain the evaluation results of the load distribution estimation by the load distribution estimation device 1 according to this embodiment. Figure 8 is a diagram summarizing the estimation results by the load distribution estimation device according to this embodiment.

[0054] In this study, to evaluate the effectiveness, the SVR30 was set in the center of the distribution line 3 between two sensor-integrated switches 20, the distance between the sensor-integrated switches 20 was set to 2 km, and the tap position of the SVR30 was fixed at 6900 V. The overall load and load power factor of the distribution line 3 were then varied.

[0055] Ideally, since this is an estimation of the load distribution, the accuracy of the load distribution estimation should be compared. However, the actual number of load points in the power distribution line 3 is greater than the three hypothetical load points, making it difficult to compare their accuracy. Therefore, if the load distribution is correctly estimated, the voltage, effective current, and reactive current values ​​measured by the sensor-integrated switch 20 should match the voltage, effective current, and reactive current values ​​at the location of the sensor-integrated switch 20 calculated based on the estimated load distribution. Thus, in this accuracy verification, the evaluation was performed using the voltage, effective current, and reactive current values ​​at the location of the sensor-integrated switch 20 based on the estimated load distribution.

[0056] Table 401 in Figure 8 shows the evaluation results at the location of the sensor-integrated switch 20 having the upstream distribution line sensor 21. Table 402 shows the evaluation results at the location of the sensor-integrated switch 20 having the downstream distribution line sensor 22. The figures in Tables 401 and 402 represent the maximum error for all cases estimated by varying the total load (4000kW to -4000kW) and load power factor (lagging 85%, 100%, leading 85%). The voltage error is a percentage of 6600V, and the power flow error is a percentage of the apparent power of the total load on distribution line 3.

[0057] As shown in graphs 401 and 402, the tap position estimation result by the tap position estimation unit 10 was 6900V at all positions, indicating that the estimation was correct. Furthermore, at all positions, the error with the measurement result from the sensor-integrated switch 20 was sufficiently small for voltage, effective current, and reactive current. Although the error in voltage was larger at the end-side sensor, it was still only 0.13%, and at high voltage it was approximately 8.6V, which is very small.

[0058] Next, the error in the event that the tap position estimation unit 10 incorrectly estimates the tap position is calculated, and the extent to which the error increases is evaluated. For example, if it incorrectly estimates 6800V, which is off by one tap, the voltage error at the terminal sensor will be approximately 2% (= approximately 132V at high voltage). If it incorrectly estimates 6700V, which is off by two taps, the error will be approximately 3.5% (= approximately 231V at high voltage). If it incorrectly estimates 6600V, which is off by three taps, the error will be approximately 5% (= approximately 330V at high voltage). Therefore, if the tap position estimation unit 10 can correctly estimate the tap position, the voltage, effective current, and ineffective current at the position of the sensor-integrated switch 20, which are obtained using the estimation results, will match the measured values, and the load distribution estimation result will be considered good.

[0059] Figure 9 shows the evaluation results of the spacing between sensor-integrated switches that allow for accurate estimation. Here, the load distribution between sensor-integrated switches 20 was considered in three patterns: uniform distribution, concentrated at the start, and concentrated at the end. The maximum distance between sensor-integrated switches 20 when the tap position estimation unit 10 was able to correctly estimate the tap position was measured. In Tables 501 to 503, the vertical column represents the total load active power of the distribution line 3, and the horizontal column represents the load power factor. The numbers in the tables represent the maximum inter-center distance at which the tap position could be correctly estimated. The unit of distance is km. A larger number in the table indicates that the tap position can be accurately estimated even if the distance between sensor-integrated switches 20 is long, while a smaller number indicates that it is difficult to accurately estimate unless the distance between sensor-integrated switches 20 is shortened.

[0060] As shown in Tables 501-503, in some extreme cases the distance between the sensor-integrated switches 20 was less than 2 km, but in many cases it is possible to estimate the distance by assuming it is 2 km.

[0061] As described above, the load distribution estimation device according to this embodiment estimates the voltage of the downstream distribution line sensor by assuming a state in which the effective and reactive power flows between distribution line sensors are evenly distributed under conditions in which an SVR is not installed. The load distribution estimation device then compares the measured value and the estimated value of the voltage of the downstream distribution line sensor to estimate the position of the SVR tap. Subsequently, the load distribution estimation device estimates the load distribution between distribution line sensors using the estimated tap position.

[0062] This allows for accurate estimation of SVR tap positions, improving the accuracy of load distribution estimation. Furthermore, by using this estimated load distribution to analyze the power distribution system, the accuracy of the power distribution system analysis tool improves, enabling the maintenance of power quality.

[0063] (Hardware configuration) Figure 10 is a hardware configuration diagram of the load distribution estimation device. As shown in Figure 10, the load distribution estimation device 1 according to this embodiment includes, for example, a CPU (Central Processing Unit) 91, memory 92, a hard disk 93, and a network interface 94. The CPU 91 is connected to the memory 92, hard disk 93, and network interface 94 via a bus.

[0064] The network interface 94 is an interface for communication between the load distribution estimation device 1 and external devices. For example, the network interface 94 relays communication between the CPU 91 and the sensor-integrated switch 20.

[0065] The hard disk 93 is an auxiliary storage device. The hard disk 93 stores various programs, including programs for realizing the functions of the tap position estimation unit 10 and the load distribution estimation unit 11, which include the pre-processing unit 101, voltage estimation unit 102, and tap position determination unit 103 as illustrated in Figure 1.

[0066] Memory 92 is the main memory. Memory 92 can be, for example, DRAM (Dynamic Random Access Memory).

[0067] The CPU 91 reads various programs from the hard disk 93, loads them into memory 92, and executes them. This allows the CPU 91 to implement the functions of the tap position estimation unit 10, which includes the preprocessing unit 101, voltage estimation unit 102, and tap position determination unit 103, and the load distribution estimation unit 11, as exemplified in 1. [Explanation of Symbols]

[0068] 1 Load distribution estimation device 10 Tap position estimation unit 11 Load distribution estimation section 20. Sensor-integrated switch 21 Upstream distribution line sensor 22 Downstream distribution line sensor 30 SVR 101 Pre-processing section 102 Voltage Estimation Unit 103 Tap position determination unit

Claims

1. A pre-processing unit acquires information on effective and ineffective power flow at each location from each of two power line sensors placed on a power line, and generates a power flow model in which the difference in effective and ineffective power flow is evenly distributed between the power line sensors. A voltage estimation unit performs power flow calculations based on the power flow model generated by the preprocessing unit to obtain an estimated voltage at the location of one of the power distribution line sensors, A tap position determination unit that obtains a voltage measurement value from one of the distribution line sensors and determines the tap position of an automatic voltage regulator for power distribution placed between the distribution line sensors based on the difference between the measurement value and the estimated value, A load distribution estimation unit estimates the load distribution between the distribution line sensors based on the tap position determined by the tap position determination unit, and the information on the effective and ineffective power flow at each of the two distribution line sensors. A load distribution estimation device characterized by being equipped with the following features.

2. The two distribution line sensors include an upstream distribution line sensor and a downstream distribution line sensor, according to the direction of current flow. The voltage estimation unit obtains an estimated voltage at the location of the downstream power distribution line sensor, The tap position determination unit acquires a voltage measurement value from the downstream distribution line sensor and determines the tap position of the automatic voltage regulator for power distribution, which is located between the upstream distribution line sensor and the downstream distribution line sensor, based on the difference between the measurement value and the estimated value. The load distribution estimation unit estimates the load distribution between the upstream distribution line sensor and the downstream distribution line sensor based on the tap position and the information on the effective and ineffective power flow at the respective positions of the upstream distribution line sensor and the downstream distribution line sensor. The load distribution estimation device according to feature 1.

3. The load distribution estimation device according to claim 1 or 2, characterized in that the tap position determination unit has in advance information on the correspondence between a range of voltage values ​​and the tap position, and determines the tap position corresponding to the difference between the measured value and the estimated value based on the correspondence.

4. The load distribution estimation device according to any one of 1 to 3, characterized in that the preprocessing unit generates the power flow model such that the effective power flow and the ineffective power flow decrease by a value obtained by dividing the difference in effective power flow and the difference in ineffective power flow by the number of division positions up to the division positions that divide the distance between the power distribution line sensors into equal parts.

5. Information on effective and ineffective power flow at each location is obtained from each of two power line sensors placed on the power line, and a power flow model is generated in which the difference in effective and ineffective power flow is evenly distributed between the power line sensors. Based on the generated power flow model, a power flow calculation is performed to obtain an estimated voltage at the location of one of the power distribution line sensors. A voltage measurement is obtained from one of the distribution line sensors, and the tap position of the automatic voltage regulator for power distribution, which is placed between the distribution line sensors, is determined based on the difference between the measurement and the estimated value. Based on the determined tap position and the information on the effective and ineffective power flow at each of the two power distribution line sensors, the load distribution between the power distribution line sensors is estimated. A method for estimating load distribution characterized by the following:

6. Information on effective and ineffective power flow at each location is obtained from each of two power line sensors placed on the power line, and a power flow model is generated in which the difference in effective and ineffective power flow is evenly distributed between the power line sensors. Based on the generated power flow model, a power flow calculation is performed to obtain an estimated voltage at the location of one of the power distribution line sensors. A voltage measurement is obtained from one of the distribution line sensors, and the tap position of the automatic voltage regulator for power distribution, which is placed between the distribution line sensors, is determined based on the difference between the measurement and the estimated value. Based on the determined tap position and the information on the effective and ineffective power flow at each of the two power distribution line sensors, the load distribution between the power distribution line sensors is estimated. A load distribution estimation program characterized by having a computer perform the processing.

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