Loop lateral-flow current calculation device, loop lateral-flow current calculation method, and loop lateral-flow current calculation program

Abstract

The purpose of the technology of the present disclosure is to calculate a loop lateral-flow current at high accuracy in a short time. A loop lateral-flow current calculation device (101) calculates a loop lateral-flow current that flows when loop switching is performed between two power distribution systems connected to substations belonging to different host systems, the device comprising: a state setting unit (13) that sets a voltage state before the loop switching of the target substations provided for the two power distribution systems; a model generation unit (14) that generates equivalent circuits to the host systems by using a first slack node, and a branch and / or a second slack node; a tuning unit (15) that decides on a parameter for the equivalent circuits to the host systems such that a voltage state, which is before the loop switching of the target substations and calculated using the equivalent circuits to the host systems, matches the voltage state which has been set; and a load-flow calculation unit (16) that calculates a loop lateral-flow current through load-flow calculation by using the equivalent circuits to the host systems and the two power distribution systems.

Description

Loop cross current calculation device, loop cross current calculation method, and loop cross current calculation program

[0001] The present disclosure relates to the calculation of loop cross currents.

[0002] Distribution systems have switches installed at loop points. When the switches are open, the distribution system is radial. When the system configuration needs to be changed for construction or other reasons, the switch is closed to perform loop switching, temporarily putting the distribution system into a loop state. Depending on the loop cross current flowing through the distribution system in a loop state, it may cause the overcurrent relay at the substation to malfunction, resulting in a power outage. To prevent this, operators must estimate the loop cross current or loop point phase difference before loop switching, determine whether loop switching is possible, and then plan construction and other work.

[0003] In particular, when performing loop switching between distribution systems connected to different upstream systems (hereinafter also referred to as "different systems"), the state of the upstream system must be taken into consideration. In the future, as renewable energy and electric vehicles (EVs) become more widely adopted, the power flow distribution within the system will change in complex ways, so when determining whether or not to switch the loop, it will be necessary to accurately estimate the loop cross current depending on the situation.

[0004] Patent Document 1 discloses a system that acquires information from the upper system, such as the total impedance of the system (ΣZ) and the total integrated value of the impedance and power flow (P) (ΣZ·P), calculates the loop cross current from these values ​​using simple calculations, and determines whether the loop cross current plus the load current of the distribution line is below an allowable value, thereby determining whether loop switching is possible.

[0005] JP 2012-90386 A

[0006] In the technology described in Patent Document 1, the calculation formula is a scalar calculation that includes divisions, the state of the controller is not reflected in the calculation, and the phase difference is not taken into account in the calculation, so it is thought that calculation errors may be included in the loop cross current.

[0007] The most accurate calculation of loop current can be achieved by using a power flow model that includes the state of the upper system and the controller. However, power flow calculations for large loop systems take a long time.

[0008] The technology of the present disclosure has been developed in consideration of the above-mentioned problems, and aims to calculate loop cross currents with high accuracy and in a short time.

[0009] The loop cross current calculation device disclosed herein is a device that calculates the loop cross current that flows when a switch located at a loop point between two distribution systems connected to different substations in an upper system is closed to perform loop switching, and includes: a state setting unit that sets the voltage state before loop switching of a target substation located in the two distribution systems; a model generation unit that generates an equivalent circuit of the upper system using a first slack node and at least one of a branch or a second slack node; a tuning unit that determines the parameters of the equivalent circuit of the upper system so that the voltage state before loop switching of the target substation calculated using the equivalent circuit of the upper system matches the set voltage state; and a power flow calculation unit that calculates the loop cross current by power flow calculation using the equivalent circuit of the upper system and the two distribution systems.

[0010] The loop cross current calculation device of the present disclosure can calculate the loop cross current with high accuracy and in a short time by using an equivalent circuit of a higher-level system. Objects, features, aspects, and advantages of the present disclosure will become more apparent from the following detailed description and the accompanying drawings.

[0011] FIG. 1 is a configuration diagram of a power system. FIG. 2 is a diagram showing the configuration of a loop cross current calculation device according to a first embodiment. FIG. 3 is a flowchart showing the operation of the loop cross current calculation device according to the first embodiment. FIG. 4 is a diagram showing the configuration of a power system in which an upper system is represented by one slack node and one branch. FIG. 5 is a diagram showing the configuration of a power system in which an upper system is represented by one slack node, one branch, and one aggregated load. FIG. 6 is a diagram showing the configuration of a power system in which a section other than the loop section of a distribution system is equivalently contracted. FIG. 7 is a diagram showing the configuration of a loop cross current calculation device according to a second embodiment. FIG. 8 is a flowchart showing the operation of the loop cross current calculation device according to the second embodiment. FIG. 9 is a diagram showing the hardware configuration of a loop cross current calculation device. FIG. 10 is a diagram showing the hardware configuration of a loop cross current calculation device.

[0012] <A. First Embodiment> Fig. 1 is a diagram showing a power system for which a loop cross current calculation device according to a first embodiment calculates a loop cross current. Upper-level system substations 1a and 1b are connected to a 154 kV transmission line 21. Branch lines 6a, 6b, and 6f are connected to the transmission line 21.

[0013] The upper-system substation 1a reduces the voltage of electricity sent from the transmission line 21 (primary side) from 154 kV to typically 66 kV or 77 kV and outputs it to the secondary-side transmission line 3a. A distribution substation 2a is connected to the secondary side of the upper-system substation 1a via the transmission line 3a. A distribution line 4a is connected to the secondary side of the distribution substation 2a. A branch line 6c is connected to the transmission line 3a. Branch lines 6d and 6e are connected to the distribution line 4a.

[0014] Similarly, the upper-system substation 1b steps down the voltage of electricity sent from the transmission line 21 (primary side) from 154 kV to typically 66 kV or 77 kV and outputs it to the secondary-side transmission line 3b. A distribution substation 2b is connected to the secondary side of the upper-system substation 1b via the transmission line 3b. A distribution line 4b is connected to the secondary side of the distribution substation 2b. A branch line 6g is connected to the transmission line 3b. A branch line 6i is connected to the distribution line 4b. A high-voltage automatic voltage regulator (SVR: Step Voltage Regulator) 5 is also installed on the distribution line 4b. The distribution lines 4a and 4b are connected via a switch installed at a loop point RP. Under normal circumstances, this switch is open, and the distribution lines 4a and 4b are not conducting. When the loop is switched, the switch is turned on, forming a loop section consisting of the conductive distribution lines 4a and 4b, through which a loop cross current flows. The loop cross current calculation device according to the first embodiment calculates this loop cross current with high accuracy.

[0015] In the above power system, the transmission line 21, the upper system substations 1a and 1b, and the transmission lines 3a and 3b form the upper system, and the distribution substations 2a and 2b, the distribution lines 4a and 4b, and the SVR 5 form the distribution system.

[0016] 2 is a diagram showing an example of the configuration of the loop cross current calculation device 101 according to embodiment 1. The loop cross current calculation device 101 will be described below with reference to Fig. 2. The loop cross current calculation device 101 is configured to include a calculation unit 11, a storage unit 17, and an output unit 19.

[0017] The calculation unit 11 calculates the loop cross current of the power distribution system based on the data acquired from the storage unit 17 .

[0018] The storage unit 17 stores data necessary for the calculation unit 11 to calculate the loop cross current of the distribution system. The storage unit 17 includes a distribution system database 18. The distribution system database 18 stores system information of the distribution system used to perform power flow calculations of the distribution system, such as distribution line topology, distribution line impedance, load information of each node, power generation information of each node, installation locations of SVRs which are voltage controllers, SVR tap information, sensor measurement values ​​in the distribution line, and data on voltage states between distribution substations that are loop switching targets.

[0019] The output unit 19 outputs the calculation result of the loop cross current obtained by the calculation unit 11 .

[0020] The calculation unit 11 includes an equivalent circuit generation unit 12 and a power flow calculation unit 16. The equivalent circuit generation unit 12 includes a state setting unit 13, a model generation unit 14, and a tuning unit 15.

[0021] The state setting unit 13 determines the voltage state of the upper system before loop switching based on the system information of the distribution system acquired from the storage unit 17 and the sensor measurement values ​​in the distribution line. Here, the voltage state of the upper system refers to at least one of the voltage and voltage phase of the distribution substations 2a, 2b that are the loop switching targets. The state setting unit 13 determines the voltage phase of the distribution substations 2a, 2b taking into account the voltage phase difference between the distribution substations 2a, 2b. A specific example of the procedure will be described with reference to FIGS. 4 and 5.

[0022] The model generation unit 14 generates an equivalent circuit of a higher-level system using one slack node (hereinafter referred to as a "first slack node") and at least one branch or one slack node (hereinafter referred to as a "second slack node"). Examples of generating equivalent circuits will be described in detail when explaining FIGS. 4 to 6.

[0023] The tuning unit 15 tunes either the impedance (resistance R, inductive reactance XL, capacitive reactance XC) of the branch of the equivalent circuit generated by the model generation unit 14 or the designated value of the slack node so as to satisfy the voltage state set by the state setting unit 13. A specific example of the tuning procedure will be described in detail when explaining FIGS. 4 to 6.

[0024] The power flow calculation unit 16 performs power flow calculations using the equivalent circuit of the upper system generated by the equivalent circuit generation unit 12 and the power distribution system, and calculates the loop cross current.

[0025] 3 is a flowchart showing the calculation process of the loop cross current by the loop cross current calculation device 101. The calculation process of the loop cross current by the loop cross current calculation device 101 will be described below with reference to the flow of FIG.

[0026] First, in the processes of steps S101 to S103, the equivalent circuit generating unit 12 generates an equivalent circuit of the upper system.

[0027] Specifically, in step S101, the state setting unit 13 determines the voltage state before loop switching of the distribution substations 2 a and 2 b that are the target of loop switching. Here, the voltage state includes at least one of the voltage and the voltage phase.

[0028] Next, in step S102, the model generating unit 14 generates an equivalent circuit of a higher-level system using the first slack node and at least one of the branch and the second slack node.

[0029] Thereafter, in step S103, the tuning unit 15 tunes the parameters of the equivalent circuit so that the voltage state of the upper system set by the state setting unit 13 is satisfied. The parameters to be tuned here are the impedances (X, L, C) of the branch and the designated values ​​of the first slack node and the second slack node. Examples of the processing from step S101 to step S103 will be described in detail when describing FIGS. 4 to 6.

[0030] Next, in step S104, the power flow calculation unit 16 calculates the loop cross current by performing a power flow calculation for the system during loop switching using the equivalent circuit of the upper system tuned in step S103 and the distribution system that is the loop switching target. An example of the processing in step S104 will be described in detail when explaining FIG. 6.

[0031] Thereafter, in step S105, the output unit 19 outputs the calculation result of the loop cross current.

[0032] 4 to 6 show examples of equivalent circuits of upper-level systems generated by the model generation unit 14. In these figures, the upper-level system is replaced with an equivalent circuit in the power system shown in FIG. 1. The model generation unit 14 generates the equivalent circuit of the upper-level system using a first slack node and at least one of a branch and a second slack node. Therefore, although a minimum configuration is shown in FIGS. 4 to 6, branches or slack nodes may be added in addition to the branches or slack nodes shown in these figures.

[0033] 4, the upper system is simulated by a first slack node 31 and a branch 32. Because the first slack node 31 is a voltage source, a voltage and a voltage phase are set for the first slack node 31. The branch 32 is simulated by an impedance, and the impedance of the branch 32 may include at least one of a resistance value R, an inductive reactance XL, and a capacitive reactance XC.

[0034] 4, the state setting unit 13 sets the voltage state of the primary side of each of the distribution substations 2a and 2b before the loop switching. The tuning unit 15 determines the parameters of the equivalent circuit so that the set value of the state setting unit 13 for the voltage state of the primary side of each of the distribution substations 2a and 2b before the loop switching matches the value calculated from the equivalent circuit. The parameters determined here are at least one of the voltage and voltage phase of the first slack node 31 and at least one of the resistance value R, inductive reactance XL, and capacitive reactance XC of the branch 32.

[0035] The state setting unit 13 may set the primary side voltage and voltage phase of the distribution substations 2a and 2b before loop switching based on past measurement values ​​of measuring instruments installed in the distribution substations 2a and 2b. The state setting unit 13 may also calculate the primary side voltage and voltage phase of the distribution substations 2a and 2b by performing a power flow calculation of the distribution system, calculating voltage changes and voltage phase changes in the distribution lines 4a and 4b, and adding these to the measurement values ​​of the loop point RP of the distribution lines 4a and 4b. Note that the method of calculating the primary side voltage and voltage phase of the distribution substations 2a and 2b is not limited to the above.

[0036] The state setting unit 13 may determine the voltage or voltage phase for one case, or may determine the voltage or voltage phase for multiple cases taking into consideration the date and time when loop switching is scheduled to be performed, weather, uncertainty, the state of the voltage controller, etc. The conditions assumed when determining the voltage or voltage phase for multiple cases are not limited to the time, weather, uncertainty, or the state of the voltage controller.

[0037] The tuning unit 15 may perform a power flow calculation while gradually changing the parameter values ​​of the equivalent circuit to search for parameters that minimize the error of the calculation result from the specified value. Alternatively, the tuning unit 15 may calculate parameters that minimize the error of the calculation result from the specified value through mathematical optimization. Note that the method of tuning the parameters by the tuning unit 15 is not limited to these. When the tuning unit 15 performs a power flow calculation during the parameter tuning process, the power flow calculation may also include a distribution system, which is a lower-level system, and the distribution system may be treated as a contracted load.

[0038] When tuning parameters to satisfy the voltage phases θ1 and θ2 of the distribution substations 2a and 2b set by the state setting unit 13, the tuning unit 15 may set the voltage of the first slack node 31 to 1 pu, match the voltage phase of the first slack node 31 with the voltage phase θ1 of the distribution substation 2a, and tune only at least one of the resistance value R, inductive reactance XL, and capacitive reactance XC of the branch 32. This reduces the number of tuning parameters.

[0039] If the state setting unit 13 sets multiple cases of the primary-side voltage and voltage phase before loop switching in the distribution substations 2 a and 2 b, the tuning unit 15 may tune the parameters for each case, or may tune the parameters based on a criterion such as minimizing the sum of squares of the errors for each case or minimizing the maximum error for each case. Furthermore, if multiple parameter combinations exist that minimize the errors from the specified values, the tuning unit 15 may output these multiple parameter combinations, and the power flow calculation unit 16 may subsequently perform cross current calculations for the multiple parameter combinations. The output unit 19 may then output one parameter combination based on a unique criterion, such as adopting a parameter combination whose impedance value is closest to that of the actual system, or may output the top five combinations with the smallest errors. The unique criterion is not limited to the above.

[0040] In Fig. 5, the upper system is simulated by a first slack node 31, a branch 32, and an aggregated load 33. In Fig. 5, the aggregated load 33 is installed on the primary side of the distribution substation 2b, but it may be installed elsewhere. The aggregated load 33 is represented by one or more elements of active power P, reactive power Q, active current, reactive current, resistance R, inductive reactance XL, and capacitive reactance XC. The processing of the state setting unit 13 in Fig. 5 is the same as that described in Fig. 4.

[0041] The tuning unit 15 determines the parameters of the equivalent circuit so that the set value of the state setting unit 13 for the voltage state on the primary side of the distribution substations 2a and 2b before loop switching matches the value calculated from the equivalent circuit. The parameters to be determined here are at least one of the voltage and voltage phase of the first slack node 31, at least one of the resistance value R, inductive reactance XL, and capacitive reactance XC of the branch 32, and at least one of the active power P, reactive power Q, active current, reactive current, resistance value R, inductive reactance XL, and capacitive reactance XC of the aggregated load 33. The method of determining the parameters in the case of Figure 5 is the same as that in the case of Figure 4.

[0042] In Fig. 6, the upper system is simulated by a first slack node 31 and a second slack node 34. At least one of the first slack node 31 and the second slack node 34 is a voltage source for which a voltage and a voltage phase are specified. A voltage and a voltage phase may be specified for both the first slack node 31 and the second slack node 34. A combination of a voltage or a voltage phase and an active power or a reactive power may be specified for either the first slack node 31 or the second slack node 34. The processing of the state setting unit 13 in the case of Fig. 6 is the same as that described in Fig. 4.

[0043] The tuning unit 15 determines the parameters of the equivalent circuit so that the set value of the state setting unit 13 and the value calculated from the equivalent circuit match, regarding the voltage state on the primary side of the distribution substations 2a and 2b before loop switching. The parameters determined here are the designated values ​​of the first slack node 31 and the second slack node 34. The method of determining the parameters in the case of Figure 6 is the same as that in the case of Figure 4.

[0044] 7 shows a power system in which the power flow calculation unit 16 calculates the loop cross current. In this case, the distribution lines other than the loop section in the power distribution system are equivalently contracted.

[0045] The power flow calculation unit 16 performs power flow calculations for the looped system using the distribution system and the equivalent circuit of the upper system generated and tuned by the equivalent circuit generation unit 12. The amount of calculation required for power flow calculations that can analyze the looped system tends to increase exponentially with the scale of the system. Therefore, the power flow calculation unit 16 reduces the amount of calculation required for power flow calculations by equivalently reducing the distribution system as described above and reducing its scale.

[0046] In Fig. 7, the upper system is shown as an equivalent circuit consisting of the first slack node 31 and the branch 32 as shown in Fig. 4, but is not limited to this. In the power distribution system shown in Fig. 7, the branch lines 6d, 6e, 6i, and 6h other than the distribution lines 4a and 4b included in the loop section are contracted and simulated by node loads 14d, 14e, 14i, and 14h.

[0047] The power flow calculation unit 16 may calculate the active power and reactive power flowing into branch lines that are not included in the loop section by performing a power flow calculation on the distribution system before loop switching, and set these values ​​as the node load. The power flow calculation unit 16 may also add up the load and power generation information of consumers in the branch lines to set the node load. Note that the method for setting the node load is not limited to these.

[0048] If the state setting unit 13 sets the voltage state on the primary side of the distribution substations 2a, 2b for multiple cases, or if the tuning unit 15 provides multiple tuning results for the parameters of the equivalent circuit of the upper system, the power flow calculation unit 16 may perform a power flow calculation for each set voltage state or tuning result and evaluate the loop cross current.

[0049] Furthermore, the power flow calculation unit 16 may perform the power flow calculation using, as simulation parameters, the tap positions of the load ratio control transformers (LRTs) in the distribution substations 2 a and 2 b, the tap position states of the SVRs 5 in the distribution lines 4 a and 4 b, the power generation amounts, suppression control amounts, power factor / reactive power control amounts, or demand suppression amounts of the distributed power sources in the distribution lines 4 a and 4 b.

[0050] Furthermore, the power flow calculation unit 16 may perform a power flow calculation before the loop in addition to analyzing the cross current in the loop before performing the power flow calculation in step S104. This enables the output unit 19 to output not only the loop cross current of the distribution system but also the voltage and current conditions before the loop and notify the operator.

[0051] <B. Second Embodiment> Figure 8 is a configuration diagram of a loop cross current calculation device 102 according to a second embodiment. The loop cross current calculation device 102 differs from the loop cross current calculation device 101 according to the first embodiment in that the memory unit 17 includes a power transmission system database 20 in addition to a power distribution system database 18.

[0052] The power transmission system database 20 stores at least upper system information necessary for performing power flow calculations for the power transmission system (upper system). The upper system information includes, for example, transmission line topology, transmission line impedance, load and power generation information for each node, generator information, SVR installation locations, SVR tap information, phase modifying equipment, or sensor measurement values ​​within the transmission line. The load and power generation information for each node and the sensor measurement values ​​within the transmission line may be time-series data.

[0053] In the first embodiment, the power flow calculation unit 16 performs power flow calculations for the system during loop switching using the equivalent circuit of the upper system and the distribution system, and calculates the loop cross current. In the second embodiment, in addition to the processing of the first embodiment, the power flow calculation unit 16 analyzes the voltage and current states of the upper system by power flow calculations using information on the upper system.

[0054] Therefore, when setting the voltage state before loop switching of the substation to be switched over, the state setting unit 13 can use the voltage and current state of the upper system analyzed by the power flow calculation unit 16, and measurement information of the distribution substations 2a, 2b or the loop point RP is not required.

[0055] The power transmission system database 20 and the power distribution system database 18 may be installed separately, such as one installed in a power supply control center and the other installed in a power distribution control center, or may be installed in the same location. Also, the power transmission system database 20 and the power distribution system database 18 may be integrated into a single database.

[0056] Fig. 9 is a flowchart of the loop cross current calculation process performed by the loop cross current calculation device 102. The flow in Fig. 9 is the same as the flow in Fig. 3 described in the first embodiment, except that step S111 is added before step S101.

[0057] In step S111, the power flow calculation unit 16 performs a power flow calculation using the higher-level system information to calculate the voltage distribution and current distribution of the higher-level system before the loop switching. Input data for the power flow calculation includes, for example, but is not limited to, the load or power generation amount of each node assumed at the time of the loop switching, the generator output, control parameters, the power transmission system topology, the transformer tap position, or the on state of the phase modifying equipment. The power flow calculation unit 16 may assume multiple states at the time of the loop switching and perform power flow calculations for multiple cases.

[0058] Next, in step S101, the state setting unit 13 refers to the power flow calculation result in step S111 and determines the voltage state before loop switching of the distribution substations 2a and 2b that are the target of loop switching.

[0059] The subsequent processing from step S102 onwards is the same as in the first embodiment.

[0060] <C. Hardware Configuration> The calculation unit 11, memory unit 17, and output unit 19 in the above-described loop cross current calculation devices 101, 102 are realized by a processing circuit 81 shown in FIG. 10. That is, the processing circuit 81 includes the calculation unit 11, memory unit 17, and output unit 19 (hereinafter referred to as the "calculation unit 11, etc."). The processing circuit 81 may be implemented using dedicated hardware, or may be implemented using a processor that executes a program stored in memory. Examples of the processor include a central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, DSP (Digital Signal Processor), etc.

[0061] When the processing circuitry 81 is dedicated hardware, the processing circuitry 81 may be, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof. Each function of each unit such as the calculation unit 11 may be realized by a plurality of processing circuits 81, or the functions of each unit may be realized together by a single processing circuit.

[0062] When the processing circuit 81 is a processor, the functions of the calculation unit 11 and other components are realized by software (software, firmware, or a combination of software and firmware). The software is written as a program and stored in memory. As shown in FIG. 11 , the processor 82 applied to the processing circuit 81 realizes the functions of each component by reading and executing a program stored in memory 83. That is, the loop cross current calculation devices 101 and 102 each include a memory 83 for storing a program that, when executed by the processing circuit 81, results in the functions of the calculation unit 11 and other components being performed. In other words, the program causes a computer to execute the procedure or method of the calculation unit 11 and other components. Here, the memory 83 may be, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable Read Only Memory), or an EEPROM (Electrically Erasable Programmable Read Only Memory), a HDD (Hard Disk Drive), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD (Digital Versatile Disk) and its drive device, or any storage medium that will be used in the future.

[0063] The above describes a configuration in which each function of the calculation unit 11, etc. is realized either by hardware or software, etc. However, the present invention is not limited to this, and a configuration in which part of the calculation unit 11, etc. is realized by dedicated hardware and another part is realized by software, etc. For example, the calculation unit 11 may be realized by a processing circuit as dedicated hardware, and the remaining functions may be realized by the processing circuit 81 as the processor 82 reading and executing a program stored in the memory 83.

[0064] It should be noted that the embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate. The above description is an example in all respects. It is understood that countless variations not illustrated can be envisioned.

[0065] 1a, 1b Upper system substation, 2a, 2b Distribution substation, 3a, 3b, 21 Transmission line, 4a, 4b Distribution line, 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h, 6i Branch line, 11 Calculation unit, 12 Equivalent circuit generation unit, 13 State setting unit, 14 Model generation unit, 14d Node load, 14e Node load, 14h Node load, 14i Node load, 15 Tuning unit, 16 Power flow calculation unit, 17 Storage unit, 18 Distribution system database, 19 Output unit, 20 Transmission system database, 31 First slack node, 32 Branch, 33 Aggregated load, 34 Second slack node, 81 Processing circuit, 82 Processor, 83 Memory, 101, 102 Loop cross current calculation device.

Claims

1. A device for calculating a loop cross current that flows when a switch located at a loop point between two distribution systems connected to different substations in an upper system is closed to perform loop switching, comprising: a state setting unit that sets the voltage state before loop switching of a target substation located in the two distribution systems; a model generation unit that generates an equivalent circuit of the upper system using a first slack node and at least one of a branch or a second slack node; a tuning unit that determines parameters of the equivalent circuit of the upper system so that the voltage state before loop switching of the target substation calculated using the equivalent circuit of the upper system matches the set voltage state; and a power flow calculation unit that calculates the loop cross current by power flow calculation using the equivalent circuit of the upper system and the two distribution systems.

2. The loop cross current calculation device according to claim 1, wherein the equivalent circuit of the higher-level system includes the first slack node, the branch, and a load.

3. The loop cross current calculation device according to claim 1 or claim 2, wherein the tuning unit determines at least one of the resistance value, inductive reactance, and capacitive reactance of the branch when the equivalent circuit of the higher-level system includes the branch.

4. The loop cross current calculation device according to claim 2, wherein the tuning unit determines at least one of the active power, reactive power, active current, reactive current, resistance value, inductive reactance, and capacitive reactance of the load.

5. A loop cross current calculation device according to any one of claims 1 to 4, wherein the tuning unit determines a combination of the voltage and voltage phase, or one of the voltage and voltage phase and one of the active power and reactive power, of either the first slack node or the second slack node when the equivalent circuit of the higher-level system includes the second slack node.

6. The loop cross current calculation device according to any one of claims 1 to 5, wherein the voltage state includes a voltage and a voltage phase.

7. The loop cross current calculation device according to any one of claims 1 to 6, wherein the power flow calculation unit performs the power flow calculation using a control amount of a voltage controller connected to one of the two distribution systems as a parameter.

8. The loop cross current calculation device according to any one of claims 1 to 7, wherein the power flow calculation unit performs the power flow calculation by contracting branch lines other than the loop sections in the two distribution systems.

9. A loop cross current calculation device according to any one of claims 1 to 8, wherein the power flow calculation unit calculates the voltage distribution before loop switching of the upper system by power flow calculation using system information of the upper system as input, and the state setting unit sets the voltage state before loop switching of the target substation based on the calculation result of the voltage distribution.

10. A method for calculating a loop cross current that flows when a switch located at a loop point between two distribution systems connected to different substations in an upper system is closed to perform loop switching, the method comprising: setting a voltage state before loop switching of a target substation located in the two distribution systems; generating an equivalent circuit of the upper system using a first slack node and at least one of a branch or a second slack node; determining parameters of the equivalent circuit of the upper system so that the voltage state before loop switching of the target substation calculated using the equivalent circuit of the upper system matches the set voltage state; and calculating the loop cross current by power flow calculation using the equivalent circuit of the upper system and the two distribution systems.

11. A loop cross current calculation program that causes a computer to calculate a loop cross current that flows when a switch located at a loop point between two distribution systems connected to different substations in an upper system is closed to perform loop switching, the program comprising: causing the computer to set a voltage state before loop switching of a target substation located in the two distribution systems; generating an equivalent circuit of the upper system using a first slack node and at least one of a branch or a second slack node; determining parameters of the equivalent circuit of the upper system so that the voltage state before loop switching of the target substation calculated using the equivalent circuit of the upper system matches the set voltage state; and calculating the loop cross current by power flow calculation using the equivalent circuit of the upper system and the two distribution systems.

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