System stabilization device

Abstract

To provide a power grid stabilizer capable of keeping a stable state of a power grid even when a state of the power grid largely changes.SOLUTION: A power grid stabilizer according to an embodiment comprises a selection unit, an electrical control estimation model generation unit, an electrical control machine correction unit, a first stage electrical control execution unit, a stability evaluation model generation unit and an additional electrical control execution unit. After an accident occurs, the additional electrical control execution unit selects and cuts off an additional electrical control machine when a generator is determined to lose synchronization on the basis of model definition information prepared in the stability evaluation model generation unit, a transition of phase angle deviation calculated using a measured value of a power grid, and a determination criterion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a power system stabilization device. [Background technology]

[0002] When a power system fault, such as a short circuit or ground fault caused by a lightning strike, occurs, the generators in the power system may enter an unstable state called a step-out. If the step-out is left unchecked, the entire power system may fall into an unstable state. In such cases, a power system stabilization device is known that controls some of the generators in the power system and cuts off the power supply from the controlled generators, thereby maintaining stable operation of most of the power system.

[0003] A grid stabilization device acquires grid information about a power grid at a preset cycle. Using the grid information, the grid stabilization device calculates transient stability in the event of a grid fault in a grid model, which is a simulation model that represents the power flow state of the power grid. The grid stabilization device determines whether a generator will lose synchronism based on the calculation result of transient stability. If a generator loses synchronism, the grid stabilization device selects a shearing control unit required to maintain the power grid in a stable state. Then, in the event of a grid fault, the grid stabilization device maintains the power grid in a stable state by cutting off the supply of power from the selected shearing control unit (Non-Patent Document 1).

[0004] However, there are cases where the state of the power system changes significantly during the period in which the necessary shearing control machines are selected. The shearing control machines selected in advance using the method of Non-Patent Document 1 may not be able to maintain the power system in a stable state, meaning that it may become necessary to add more shearing control machines. As an improvement measure for stabilizing the power system, a method is known in which the necessary shearing control amount is calculated at shorter intervals and the necessary shearing control machines are added or changed to the pre-selected shearing control machines before an accident occurs (Patent Documents 1 and 2). Another known method is to select a new shearing control machine when it is determined that it is difficult to maintain a stable state based on measurement information after an accident occurs, and then trip the new shearing control machine after tripping the shearing control machine selected in advance using the method of Non-Patent Document 1 (Patent Document 3).

[0005] In order to respond to various changes in the state of the power grid, it is possible to combine the above-mentioned method of adding or changing necessary shearing control machines before an accident occurs with the method of shutting off new shearing control machines after shutting off pre-selected shearing control machines.However, if Patent Document 1, which adds or changes shearing control machines for renewable energy, and Patent Document 2, which adds or changes shearing control machines for synchronous generators, are simply combined, the necessary additions and changes will be made in both, resulting in an issue of excessive shearing control machines. The method of disconnecting new shearing machines in Patent Document 3 does not assume that shearing machines will be added or changed, so there is a problem in that evaluation is performed using shearing machines before they are added or changed, and new shearing machines are excessively selected and disconnected. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2021-69214 [Patent Document 2] Patent No. 7002989 [Patent Document 3] Japanese Patent Publication No. 2022-38125 [Non-patent literature]

[0007] [Non-Patent Document 1] "Appendix 2: Examples of Relay Systems for Preventing Loss of Step," Institute of Electrical Engineers of Japan Technical Report, No. 801, October 2000, pp. 153-154 Summary of the Invention [Problem to be solved by the invention]

[0008] The problem to be solved by the present invention is to provide a power system stabilization device that can maintain a stable state of the power system even if the state of the power system changes significantly. [Means for solving the problem]

[0009] A system stabilization device according to an embodiment includes a selection unit, a shearing control estimation model generation unit, a shearing control machine correction unit, a first-stage shearing control execution unit, a stability evaluation model generation unit, and an additional shearing control execution unit. The selection unit acquires system information representing the characteristics of a power system having generators at a predetermined cycle, uses the system information to create a system model that is a simulation model representing the power flow state of the power system, calculates transient stability in the event of a predetermined system fault in the system model, and selects a first shearing control machine from the generators to cut off the power supply for each predetermined system fault based on the calculation result of the transient stability. The shearing control estimation model generation unit creates a regression equation for predicting a shearing control machine from the system information, based on shearing control machine information that is a combination of the system information and a first shearing control machine candidate for each predetermined system fault in the system model. The shearing control machine correction unit calculates the shearing control amount necessary to maintain the stability of the power system using the regression equation, the system information last acquired by the selection unit, and the system information immediately before the occurrence of the specified system fault, and adds a new shearing control machine to the first shearing control machine or changes the first shearing control machine based on the calculated shearing control amount.The first-stage shearing control execution unit transmits a command to shut off the first shearing control machine added or changed by the shearing control machine correction unit when a system fault occurs.The stability evaluation model generation unit prepares, from the results of the most recent transient stability calculation, model definition information for determining the transition of the phase angle deviation used to determine whether a generator has lost synchronism from measured values ​​of the power system and generator before and after the fault occurs, and the judgment criteria used to determine whether a generator has lost synchronism. After an accident occurs, the additional power control execution unit selects and shuts off an additional power control machine if it is determined that the generator will lose synchronism based on the model definition information prepared by the stability evaluation model generation unit, the changes in phase angle deviation calculated using the measured values ​​of the power system, and the judgment criteria. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing the configuration of a power system stabilization device according to an embodiment; [Figure 2] 2 is a diagram showing the configuration of a first-stage shear control unit selection unit of the system stabilization device of the embodiment. FIG. [Figure 3] FIG. 2 is a diagram showing the configuration of a power control machine correction unit of the grid stabilization device according to the embodiment. [Figure 4] FIG. 2 is a diagram showing the configuration of a stability evaluation model generation unit of the power system stabilization device according to the embodiment. [Figure 5] FIG. 3 is a diagram for explaining the processing content of the electrical control synchronous machine determination unit of the grid stabilization device according to the embodiment. [Figure 6] FIG. 3 is a diagram illustrating the processing content of a power control renewable energy determination unit of the grid stabilization device according to the embodiment. [Figure 7] 3A and 3B are diagrams for explaining the processing contents of transient stability calculation of the power system stabilization device according to the embodiment. [Figure 8] 3A and 3B are diagrams for explaining the processing contents of an output change calculation unit during shearing control of the system stabilization device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a power system stabilization device according to an embodiment will be described with reference to the drawings.

[0012] FIG. 1 is a diagram showing the configuration of a power supply system according to an embodiment. As shown in FIG. 1, the power supply system includes a power system 1, a transmission system 10, and a power system stabilization device 20. The power system 1 includes information terminals 11-1, 11-2, 11-3, 11-4, and 11-5, control terminals 12-1 and 12-2, buses 2-1, 2-2, 2-3, 2-4, and 2-5, transmission lines 3-1, 3-2, 3-3, 3-4, and 3-5, transformers 4-1, 4-2, 4-3, and 4-4, generators 5-1, 5-2, 5-3, and 5-4, and circuit breakers 6-1, 6-2, 6-3, and 6-4. In the following description, when it is not necessary to distinguish between the buses 2-1, 2-2, 2-3, 2-4, 2-5, and 2-6, they will be referred to as bus 2. Furthermore, when there is no need to distinguish between the power transmission lines 3-1, 3-2, 3-3, 3-4, and 3-5, they will be referred to as power transmission line 3.

[0013] Generators 5-1, 5-2, 5-3, and 5-4 generate power using renewable energy such as solar or wind power, or non-renewable energy such as fossil fuels. Generators 5-1, 5-2, 5-3, and 5-4 supply the generated power to consumers via transmission line 3 and bus 2. In the following explanation, when there is no need to distinguish between generators 5-1, 5-2, 5-3, and 5-4, they will be referred to as generators 5. Furthermore, asynchronously connected generators such as solar or wind power will be referred to as renewable energy power sources, and synchronously connected generators such as thermal, hydroelectric, and nuclear power will be referred to as synchronous generators.

[0014] The transformer 4-1 transforms the voltage of the power generated by the generator 5-1 to a predetermined voltage. The transformer 4-2 transforms the voltage of the power generated by the generator 5-2 to a predetermined voltage. The transformer 4-3 transforms the voltage of the power generated by the generator 5-3 to a predetermined voltage. The transformer 4-4 transforms the voltage of the power generated by the generator 5-4 to a predetermined voltage. In the following description, when there is no need to distinguish between the transformers 4-1, 4-2, 4-3, and 4-4, they will be referred to as transformer 4.

[0015] Circuit breaker 6-1 cuts off the supply of power generated by generator 5-1 to consumers. Circuit breaker 6-2 cuts off the supply of power generated by generator 5-2 to consumers. Circuit breaker 6-3 cuts off the supply of power generated by generator 5-3 to consumers. Circuit breaker 6-4 cuts off the supply of power generated by generator 5-4 to consumers. In the following description, when there is no need to distinguish between circuit breakers 6-1, 6-2, 6-3, and 6-4, they will be referred to as circuit breaker 6.

[0016] The information terminal 11-1 measures information (hereinafter referred to as system information) representing the characteristics of the power system 1 that supplies power from the generator 5 to consumers via the bus 2-1. Specifically, the information terminal 11-1 measures electrical information and system information. The electrical information is information relating to the power supplied by the transmission lines 3-1, 3-2, and 3-5 connected to the bus 2-1. The system information is connection information for the transmission lines 3-1 and the like. The information terminal 11-2 measures the system information representing the characteristics of the power system 1 that supplies power from the generator 5 to consumers via the bus 2-2. Specifically, the information terminal 11-2 measures the system information including electrical information for the transmission lines 3-1 and 3-3 connected to the bus 2-2 and connection information for the transmission lines 3-1 and 3-3. The information terminal 11-3 measures the system information representing the characteristics of the power system 1 that supplies power from the generator 5 to consumers via the bus 2-3. Specifically, the information terminal 11-3 measures system information including electrical information on the transmission lines 3-2 and 3-4 connected to the bus 2-3 and connection information on the transmission lines 3-2 and 3-4. The information terminal 11-4 measures system information on the power system 1 that supplies power from the generator 5 to consumers via the bus 2-4. Specifically, the information terminal 11-4 measures system information including electrical information on the transmission lines 3-3 and circuit breakers 6-1 and 6-2 connected to the bus 2-4 and connection information on the transmission lines 3-3 and circuit breakers 6-1 and 6-2. The information terminal 11-5 measures system information on the power system 1 that supplies power from the generator 5 to consumers via the bus 2-5. Specifically, the information terminal 11-5 measures system information including electrical information on the transmission lines 3-4 and circuit breakers 6-3 and 6-4 connected to the bus 2-5 and connection information on the transmission lines 3-4 and circuit breakers 6-3 and 6-4.

[0017] Here, the electrical information included in the system information is information relating to the active and reactive power of the transmission line 3 and the transformer 4, the active and reactive power of the generator 5, the bus voltage applied to the bus 2, etc. Furthermore, the connection information included in the system information is information relating to the connection state between the transmission line 3 and the transformer 4, etc. In the following description, when there is no need to distinguish between the information terminals 11-1, 11-2, 11-3, and 11-4, they will be referred to as communication terminal 11.

[0018] Control terminal 12-1 controls circuit breakers 6-1 and 6-2 to cut off the supply of power from generators 5-1 and 5-2. Control terminal 12-2 controls circuit breakers 6-3 and 6-4 to cut off the supply of power from generators 5-3 and 5-4. In the following description, when there is no need to distinguish between control terminals 12-1 and 12-2, control terminals 12-1 and 12-2 will be referred to as control terminal 12.

[0019] In the power system 1, the area to the left of the transmission line 3-5, for which system information is not available, is called the external system. The area to the right of the transmission line 3-5, for which system information is available, is called the internal system. The external system also includes multiple buses 2, transmission lines 3, transformers 4, generators 5, etc.

[0020] The transmission system 10 includes a communication network such as a dedicated communication line or the Internet. The transmission system 10 transmits various information such as power system information between the information terminal 11 and the power system stabilization device 20, and between the control terminal 12 and the power system stabilization device 20.

[0021] The power system stabilization device 20 acquires various information such as power system information from the information terminal 11 via the transmission system 10. Based on the acquired various information, the power system stabilization device 20 determines, from among the generators 5 of the power system 1, a generator to be controlled that is necessary to maintain the stability of the power supply by the power system 1. Here, the generator to be controlled is a generator 5 that cuts off the power supply.

[0022] The power system stabilization device 20 includes a first-stage shearing control unit selection unit 30, a shearing control estimation model generation unit 40, a shearing control unit correction unit 50, a first-stage shearing control execution unit 60, a stability evaluation model generation unit 70, and an additional shearing control execution unit 80. These components are realized, for example, by a hardware processor such as a CPU (Central Processing Unit) executing a program (software), or include storage areas in various storage devices. Some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware. The program may be stored in advance in a storage device such as an HDD (Hard Disk Drive) or flash memory (a storage device with a non-transitory storage medium), or may be stored in a removable storage medium (a non-transitory storage medium) such as a DVD or CD-ROM, and installed in the storage device by inserting the storage medium into a drive device.

[0023] The configuration of the first-stage shear control machine selection unit 30 will be described with reference to FIG. The first-stage shearing control unit selection unit 30 includes a basic system memory unit 31, a system information collection unit 32, a system model creation unit 33, a stability calculation unit 34, a stabilization index change amount calculation unit 35, a renewable energy group determination unit 36, a shearing control unit selection unit 37, a calculation result collection unit 38, and a calculation result memory unit 39. The basic system storage unit 31 stores the configuration of the target power system, the transmission lines, the constants of the generators, etc. The information stored by the basic system storage unit 31 is configuration information. The system information collecting unit 32 collects system information such as active power measured by the information terminal 11 via the transmission system 10 . The system model creation unit 33 collects the basic system information from the basic system storage unit 31 and the system information from the system information collection unit 32, and creates a system model. The stability calculation unit 34 performs transient stability calculations using the system model created by the system model creation unit 33. The stabilization index change calculation unit 35 collects the calculation results of the stability calculation unit 34 and calculates a stabilization index. The stabilization index change calculation unit 35 calculates the amount of change in the stabilization index of synchronous stability when the supply of power supplied from multiple generators 5 in the power system 1 that supplies power is reduced by power control. The renewable energy group determination unit 36 ​​collects the processing results of the stabilization index change amount calculation unit 35, and groups (classifies) multiple power generators 5 based on the amount of change in the stabilization index calculated by the stabilization index change amount calculation unit 35. The shedding control unit selection unit 37 collects the calculation results of the stability calculation unit 34 and the processing results of the stability index change amount calculation unit 35, and selects a shedding control unit. The calculation result collection unit 38 collects the calculation results of the stability calculation unit 34 and the processing results of the shedding machine selection unit 37. The calculation result storage unit 39 stores the information on the target power system collected by the calculation result collection unit 38, the results of the selection of shedding machines, and the like.

[0024] The configuration of the electrical control machine correction unit 50 will be described with reference to FIG. The controlled machine correction unit 50 includes a controlled synchronous machine determination unit 51 and a controlled renewable energy determination unit 52. The control synchronous machine determination unit 51 collects system information obtained via the transmission system 10, the processing results of the first-stage control machine selection unit 30, and the processing results of the control estimation model generation unit 40, and determines the synchronous generator. The power control renewable energy determination unit 52 collects system information obtained via the transmission system 10, the processing results of the first-stage power control machine selection unit 30, and the processing results of the power control estimation model generation unit 40, and determines the renewable energy power source.

[0025] The configuration of the stability evaluation model generating unit 70 will be described with reference to FIG. The stability evaluation model generation unit 70 includes a determination criterion formulation unit 71 , an output change model formulation unit 72 , a stable side system model formulation unit 73 , and an unstable side system model formulation unit 75 . The stability evaluation model generation unit 70 collects the processing results of the first stage shear control machine selection unit 30.

[0026] The shedding estimation model generation unit 40 uses the information on the system model stored in the calculation result storage unit 39 and the shedding machine selection results to create an estimation model for determining the shedding amount.

[0027] The additional power control execution unit 80 is a functional unit that operates after a fault occurs in the power system. When a fault occurs in the power system, the additional power control execution unit 80 determines whether or not to perform additional power control after performing power control by the first power control machine, using a function or the like generated by the stability assessment model generation unit 70. When additional power control is necessary, the additional power control execution unit 80 selects the power control machine to be the target of additional power control.

[0028] (action) Here, the operation of each element included in the power system stabilization device 20 will be described. First, the operation of the first-stage shedding control unit selection unit 30 will be explained with reference to Figure 2. The first-stage shedding control unit selection unit 30 selects shedding control units to be shut off when a grid fault occurs. The pre-calculation described below refers to this series of processes. Shedding control units include synchronous generators and renewable energy sources.

[0029] The system information collection unit 32 collects state quantities such as voltage, active power, and reactive power at various points in the power system from the measurement terminal 11 via the transmission system 10 at regular intervals such as one minute.

[0030] The system model creation unit 33 combines various state quantities of the power system collected by the system information collection unit 32 with constants such as the configuration of the power system and transmission lines stored in the basic system storage unit 31. The system model creation unit 33 constructs a system model required for transient stability calculations of the power system.

[0031] The stability calculation unit 34 performs transient stability calculations for the occurrence of various pre-set assumed faults using the system model constructed by the system model creation unit 33. The stability calculation unit 34 determines whether the generator will lose synchronism or not, that is, whether the power system is stable or unstable.

[0032] The stabilization index change amount calculation unit 35 and the renewable energy group determination unit 36 ​​group together renewable energy power sources with similar stabilization effects, and set each group as a candidate for power control. Specifically, the stabilization index change amount calculation unit 35 calculates the amount of change in the stabilization index for synchronous stability when the supply of power from multiple generators 5 in the power system 1 that supplies power is reduced. First, the stabilization index change amount calculation unit 35 classifies the power flow cross section based on the system configuration (topology) of the power system 1 and the operation stop state of the generators 5. After classifying the power flow cross section as described above, the stabilization index change calculation unit 35 calculates the stabilization index change used by the renewable energy group determination unit 36 ​​to group the multiple power generators 5 for each classification of the power flow cross section of the power system 1. The stabilization index change is an index that indicates the stabilization effect due to the reduction or stoppage of the output power of the renewable energy power generation device 6.

[0033] If the results of the stability calculation unit 34 are unstable, the shedding machine selection unit 37 selects a machine to be shedding from among the generators that step out and the renewable energy power source group. As an example, the shedding machine selection unit 37 targets the generator that steps out first and the generator that steps out second in the transient stability calculation results without shedding, and calculates the amount of change in active power before and after shedding from the results of transient stability calculation in which the synchronous generators or renewable energy power source groups that are candidates for shedding are shedding. The shedding machine selection unit 37 selects the candidate for shedding with the largest amount of change as the machine to be shedding.

[0034] The calculation result collection unit 38 associates the system model used in the stability calculation unit 34, the calculation results of the stability calculation unit 34, and the shedding machine selection results of the shedding machine selection unit 37, and stores them as a single data set.

[0035] The calculation result storage unit 39 stores the system model and calculation results compiled by the calculation result collection unit 38 for a long period of time, such as one year.

[0036] The shearing control estimation model generation unit 40 creates an estimation model for determining the amount of shearing control from past system models, transient stability calculation results, shearing machine selection results, and the like stored in the calculation result storage unit 39. One example of the estimation model is a linear regression equation that obtains the amount of shearing control using branch phase difference angles as input. The branch phase difference angles are obtained by a method of approximating the product of the active power of the transmission line or transformer and its reactance. The shearing control estimation model generation unit 40 may be the same as the regression equation generation unit 30 described in Patent Document 2.

[0037] The shearing control machine correction unit 50 uses the regression equation for calculating the shearing amount created by the shearing control estimation model generation unit 40, the information stored in the calculation result storage unit 39, and system information obtained from the transmission system 10. The shearing control machine correction unit 50 calculates the shearing amount at a cycle shorter than the processing cycle of the first-stage shearing control machine selection unit 30. The shearing control machine correction unit 50 adds another shearing control machine to the shearing control machine selected by the first-stage shearing control machine selection unit 30, or changes the shearing control machine selected by the first-stage shearing control machine selection unit 30, as necessary.

[0038] The controlled synchronous machine determination unit 51, which is one of the components of the controlled machine correction unit 50, will be described. The shedding control synchronous machine determination unit 51 selects synchronous generators as candidates for shedding, adds or changes machines to be shedding controlled as necessary, and transmits the results to the first-stage shedding control execution unit 60. Specific processing contents will be described with reference to FIG.

[0039] In step S101, regression formula A corresponding to the latest system state and regression formula B corresponding to the system state at the time of pre-calculation are selected from the regression formulas created by the shedding estimation model generation unit 40 based on system information obtained from the transmission system 10. The selection method is the same as that in Patent Document 2.

[0040] In step S102, the amount of power control required in the latest system state is calculated using regression formula A and the latest system information. The calculation result is set as power control amount A.

[0041] In step S103, the amount of power control required in the system state at the time of pre-calculation is calculated using regression formula B and system information at the time of pre-calculation. This calculation result is set as power control amount B.

[0042] In step S104, the magnitudes of the power control amount A and the power control amount B are compared. If the power control amount A is greater than the power control amount B, the process proceeds to step S105. If the power control amount A is equal to or less than the power control amount B, the process ends without adding or changing the power control machine.

[0043] In step S105, a shearing control unit is added or changed so that the increase in the shearing control amount is equal to or greater than the difference between the shearing control amount A and the shearing control amount B. For example, a generator with active power greater than the difference between the shearing control amount A and the shearing control amount B and with the smallest active power is selected from the shearing control candidates set in advance, and added to the shearing control units selected by the first-stage shearing control unit selection unit 30.

[0044] As a result of the above, only when the amount of power control required in the latest system state is greater than the amount of power control required in the system state at the time of pre-calculation and more power control capacity is required than the power control capacity selected by the first-stage power control capacity selection unit 30, a power control capacity is added to increase the power control capacity.

[0045] The renewable energy control determination unit 52, which is one of the components of the power control machine correction unit 50, will be described. The power control renewable energy determining unit 52 determines renewable energy power sources as candidates for power control, adds machines to be controlled as necessary, and transmits the results to the first-stage power control executing unit 60. Specific processing contents will be described with reference to FIG.

[0046] In step S201, it is determined whether or not a renewable energy power source is included in the shedding machines selected by the first-stage shedding machine selection unit 30. If a renewable energy power source is included in the selected shedding machines, the process proceeds to step S202. If a renewable energy power source is not included in the selected shedding machines, the process ends without adding a shedding machine.

[0047] In step S202, it is determined whether the total output of the renewable energy power sources selected as shedding control units by the first-stage shedding control unit selection unit 30 has decreased due to a change in weather or the like and is now smaller than the shedding control amount required by the first-stage shedding control unit selection unit 30. If the total output of the selected renewable energy power sources is smaller than the shedding control amount, the process proceeds to step S203. If the total output of the selected renewable energy power sources is not smaller than the shedding control amount, the process ends without adding shedding control units.

[0048] In step S203, a regression equation corresponding to the latest system state is selected from the regression equations created by the shedding estimation model generation unit 40 for each renewable energy group that is a candidate for shedding, based on the system information obtained from the transmission system 10. The selection method is the same as that in Patent Document 2.

[0049] In step S204, the amount of power control is calculated for each renewable energy group that is a candidate for shedding control using the regression equation selected in step S203 and the latest grid information. At this time, the amount of power control for the renewable energy group selected by the first-stage shedding control unit selection unit 30 is also calculated using the regression equation. In this explanation, the amount of power control according to the regression equation for the renewable energy group selected by the first-stage shedding control unit selection unit 30 is assumed to be shedding control amount 0, and the amounts of power control according to the regression equation for the renewable energy groups that are candidates for shedding control units are assumed to be shedding control amount 1 and shedding control amount 2. Here, to simplify the explanation, two renewable energy groups that are candidates for shedding control units are added as needed, but three or more may be used.

[0050] In step S205, the power control amount 1 and the power control amount 2 are compared, and the renewable energy group with the smaller power control amount is selected as the renewable energy group of the machine to be controlled. In the following, the power control amount 1 is assumed to be smaller than the power control amount 2.

[0051] In step S206, a renewable energy power source is selected from the renewable energy group and added to the shedding control unit so that the required shedding amount calculated by equation (1) can be obtained by the renewable energy group with shedding amount 1. The shortage of shedding amount is the difference between the shedding amount required to maintain the stability of the grid state in the first-stage shedding control unit selection unit 30, i.e., the expected shedding amount, and the total output of the renewable energy group selected by the first-stage shedding control unit selection unit 30, i.e., the actual shedding amount. If the total output of the renewable energy group with shedding amount 1 is less than the required shedding amount in equation (1), the required shedding amount cannot be secured, so similar processing is performed so that the shortage can be obtained by the renewable energy group with shedding amount 2.

[0052]

number

[0053] As a result of the above, if a renewable energy group is selected as a control unit by the first-stage control unit selection unit 30, and the output of that renewable energy group decreases and does not meet the expected amount of control, the expected effect can be achieved by adding renewable energy power sources of other renewable energy groups to the control unit.

[0054] Next, the processing contents of the stability calculation unit 34 will be described with reference to FIG.

[0055] In step S301, the initial power flow is calculated using the system model created by the system model creation unit 33. In each of the subsequent steps, processing is also performed based on this system model.

[0056] In step S302, the initial values ​​of the generator 5 and the like are set based on the results of the power flow calculation in step S301.

[0057] In step S303, an admittance matrix (hereinafter referred to as Y matrix [Y]) is generated based on the system configuration.

[0058] In step S304, the inverse matrix [Y] of the Y matrix is ​​calculated. -1 Calculate.

[0059] In step S305, it is determined whether there has been a change in the system configuration due to a system fault, the reflection of a shedding machine, etc. If there has been a change in the system configuration, the process proceeds to step S306. If there has been no change in the system configuration, the process proceeds to step S308.

[0060] In step S306, the Y matrix [Y] is changed based on the change in the system configuration.

[0061] In step S307, the inverse matrix [Y] of the changed Y matrix is ​​calculated. -1 Calculate.

[0062] In step S308, the injection current [I] is calculated based on the initial state or the state of the generator 5, etc. one time interval ΔT before.

[0063] In step S309, the inverse matrix [Y] of the Y matrix is ​​calculated. -1 Calculate the node voltage [V] from the injected current [I].

[0064] In step S310, T end Determine whether is greater than T. end If T is greater than T, proceed to step S311. end If is not greater than T, then terminate. end is a reference value that determines when a predetermined time (cycle) has elapsed and the processing is to be terminated, and is the end time of the simulation. T is set to zero at the start of the flowchart shown in FIG.

[0065] In step S311, the states of the generator 5 and the like are calculated based on the calculated node voltages [V].

[0066] In step S312, ΔT is added to T to update the value of T, and the process proceeds to step S305. The transient stability calculation is carried out as described above.

[0067] The first-stage shearing control execution unit 60 extracts the shearing control machine corresponding to the fault that has occurred, based on the shearing control machine selection results for each assumed fault condition, which have been added or changed as necessary by the shearing control machine correction unit 50, and on the fault occurrence information obtained from the transmission system 10, and outputs a control signal to shut down the shearing control machine. The control terminal 12 that receives the control signal shuts down the corresponding generator from the system.

[0068] The stability evaluation model generation unit 70 calculates constants and the like required by the additional power control execution unit 80. The stability evaluation model generating unit 70 uses a method similar to that of the stability evaluation model generating unit 40 described in Patent Document 3. However, the processing content of the output change model formulating unit 72 differs from that described in Patent Document 3. Specifically, in Patent Document 3, the first-stage shearing control machine selected by the first-stage shearing control machine selection unit 30 is not changed. For this reason, it is sufficient to calculate the amount of change in active power output during shearing converted into a one-machine infinite bus model, which is required by the additional shearing control execution unit 80, from the transient stability calculation results for the conditions for shutting off the shearing control machine selected as the first-stage shearing control machine. In contrast, in this embodiment, the first-stage controlled machine may be changed by the shedding machine correction unit 50. For this reason, it is necessary to calculate the amount of change in active power output during shedding converted into a one-machine infinite bus model for all patterns of generators that can become the first-stage controlled machine. A method for calculating the amount of output change during shedding will be described with reference to Figure 8. FIG. 8 is a diagram for explaining the processing contents of the shedding control-time output change calculation unit 73 of the system stabilization device 20 of the embodiment.

[0069] The simplest method for calculating the amount of change in active power output during shedding converted to a one-machine infinite bus model is to perform transient stability calculations for all combinations of generators that may ultimately become the first-stage shedding machine in the processing of the shedding machine correction unit 50. However, since this takes a long time to calculate, a method that can perform the calculation in a short time has been devised.

[0070] The transient stability calculation performed by the stability calculation unit 34 obtains the behavior of the synchronous generator and the power system for about 10 to 20 seconds by repeatedly calculating the internal state of the synchronous generator, etc., and the voltage and current of the power system, etc., at calculation time intervals of 10 milliseconds, etc. The shedding-time output change calculation unit 73 calculates the amount of change in active power output at the time of shedding converted into a one-machine infinite bus model, without performing iterative calculations at calculation time intervals of 10 milliseconds, etc., using the inverse matrix of the admittance matrix (Y matrix) immediately before shedding (obtained in the transient stability calculation process) and the internal voltage of the synchronous generator.

[0071] In step S401, the inverse matrix of the Y matrix immediately before shedding, the injection current vector, the node voltage, the generator active power, and the generator internal voltage are obtained from the transient stability calculation results. The relationship between the inverse matrix of the Y matrix, the injection current vector, and the node voltage is expressed by equation (2). Here, [V] is the node voltage vector, [Y] is the Y matrix, and [I] is the injection current vector.

[0072]

number

[0073] In step S402, the active power of each generator obtained in step S401 is converted into a two-machine model of an unstable group and a stable group.

[0074] In step S403, the result of step S402 is used to calculate the active power output immediately before shedding converted into a one-machine infinite bus model, which is necessary for calculating the amount of change in active power output during shedding converted into a one-machine infinite bus model.

[0075] In step S404, one of all combinations of generators that can be the first stage shedding generator is set.

[0076] In step S405, the injection current corresponding to the generator to be sheared and controlled set in step S404 is changed to zero. This is based on the fact that the injection current from the generator to be sheared and controlled to the power grid 1 becomes zero after shearing.

[0077] In step S406, the voltage of each node is calculated using the above-mentioned equation (2).

[0078] In step S407, the active power of each generator other than the generator to be shedding controlled is calculated using equation (3). G The value newly calculated in step S406 is used for the generator internal voltage E G The value obtained in step S401 immediately before the power control is used for X G is the internal impedance of the generator, and is set during the transient stability calculation process.

[0079]

number

[0080] In step S408, the generator active power calculated in step S407 is converted into a two-machine model of an unstable group and a stable group.

[0081] In step S409, the amount of change in active power during shedding in the two-machine model of the unstable group and the stable group is calculated.

[0082] In step S410, the sharing ratio of the amount of change in active power during shedding is calculated for the stable group.

[0083] In step S411, the sharing ratio calculated in step S410 is used to calculate the active power of the two-machine model of the unstable group and the stable group immediately after shedding control.

[0084] In step S412, the active power of the two-machine model calculated in step S411 is converted into the active power of the one-machine infinite bus model.

[0085] In step S413, the amount of change in active power during shedding in the one-machine infinite bus model is calculated, and this calculated value is saved as the amount of change in active power in one of the generator combinations that can be the first-stage shedding machine, which was set in step S404.

[0086] In step S414, it is determined whether all of the generator combinations that can become first-stage shedding generators have been calculated. If all of them have been calculated, the process ends. If not all of them have been calculated, the process proceeds to step S415.

[0087] In step S415, the injection current immediately before the shearing control is set, and the state is returned to the state before the amount of change in active power during shearing control was calculated, and then the process returns to step S404.

[0088] In step S404, the next candidate is set from among the generator combinations that can become the first stage shedding generator.

[0089] In step S405 and thereafter, the amount of change in active power during power control corresponding to the set power control target is calculated in the same manner as described above.

[0090] By repeating the above process, the amount of change in active power during shedding, converted into a one-machine infinite bus model, is calculated for all combinations of generators that can become first-stage shedding machines.

[0091] Compared to obtaining similar results using transient stability calculations, this method eliminates the need for simulation of several hundred milliseconds from the initial state to the occurrence of shearing, and the need to recalculate the inverse matrix of the Y matrix, which is required when simulating shearing.

[0092] Note that a complex method is used, such as calculating the share of the active power change amount in step S410, and the active powers immediately after shedding of the unstable group and stable group obtained in step S408 are not converted to a one-machine infinite bus model and used directly, because the generator active power obtained in step S407 contains an error.

[0093] It is correct that the injection current corresponding to the generator to be shedding is set to zero after shedding. Based on this idea, in step S405, the injection current corresponding to the generator to be shedding is set to zero, but the terminal voltage of the generator to be shedding, which is included in the node voltage calculated in step S406, does not become a value that makes the injection current zero.

[0094] The generator injection current is calculated by equation (4), where I G is the injection current, E G is the generator internal voltage, V G is the generator terminal voltage, X G are the internal impedances of the generator, all of which are complex numbers.

[0095]

number

[0096] To calculate the exact state after power outage, I in Eq. (4) G is zero, that is, E G and V G It is necessary to repeat the process of setting the injection current of the generator to be shedding controlled to zero and calculating the node voltage until the difference between the above is within the allowable range.

[0097] If the increase in the time required to complete the calculation is acceptable, steps S405 and S406, which are the processing steps for calculating the node voltage, can be repeated to calculate the accurate state after shedding and to calculate the accurate generator active power.

[0098] In this case, the processing steps of steps S409, S410, and S411 are unnecessary, and the generator active power of the one-machine infinite bus model can be calculated in step S412 from the generator active powers of the unstable group and stable group obtained in step S408.

[0099] The additional shearing control execution unit 80 determines whether the system will be stable or unstable if the first-stage shearing control machine is tripped, based on the generator measurement information obtained from the transmission system 10, the constants obtained by the stability assessment model generation unit 70, and the first-stage shearing control machine determined by the shearing control machine correction unit 50. If the system will be unstable, the additional shearing control execution unit 80 selects an additional shearing control machine and transmits a control signal to trip the target. The difference from the description in Patent Document 3 is that the shearing control machine determined by the shearing control machine correction unit 50 is the first-stage shearing control machine.

[0100] (effect) According to this embodiment, the shedding control unit correction unit 50 allocates the shedding control amount to be increased based on the latest system state to the synchronous generators, and if a renewable energy group is selected as a shedding control unit by the first-stage shedding control unit selection unit 30 and the expected shedding control amount falls short due to a drop in renewable energy output, the shortfall is made up by another renewable energy group, making it possible to clearly allocate roles. This makes it possible to avoid an excessive increase in the shedding control amount that occurs when a shedding control unit correction mechanism for synchronous generators and a shedding control unit correction mechanism for renewable energy are simply combined.

[0101] Furthermore, in the stability evaluation model generation unit 70, a method requiring less calculation than transient stability calculation is used to determine the amount of change in active power during power control, thereby making it possible to avoid a significant increase in calculation time and the need for additional computers.

[0102] Next, the present embodiment will be compared with Patent Documents 1, 2, and 3, and the effects of the present embodiment will be described. In Patent Documents 1 and 2, the amount of power suppression can be reduced, but there is an issue with the ability to respond to unexpected events. In Patent Document 3, the amount of power suppression is determined to be in line with actual events, but there is an issue with the amount of power suppression being too high. Specifically, in Patent Documents 1 and 2, the amount of shedding control is increased in advance in response to changes in the grid state (the content of shedding control is determined in advance). This has the advantage of minimizing the time from the occurrence of a grid fault to shedding control (generator shutdown), thereby reducing the amount of shedding control. Generally speaking, the longer the time from the occurrence of a fault to shedding control, the greater the amount of shedding control required for stabilization. On the other hand, because a regression equation constructed from the results of pre-calculation (simulation) is used, it is difficult to reflect conditions not considered in the pre-calculation or the impact of deviations from assumptions.

[0103] On the other hand, Patent Document 3 has the advantage of being able to make a judgment based on the actual situation because it uses measurement information (such as generator active power) after the accident occurs. However, it uses measurement information for a certain period of time after the accident to perform the calculations necessary to determine stability, and also determines the amount of power control required. For this reason, power control is slower and the amount of power control is greater than in Patent Documents 1 and 2, where the content of power control is determined in advance.

[0104] In comparison with the above-mentioned Patent Documents 1, 2, and 3, the present embodiment has the advantages of Patent Documents 1, 2, and 3. When increasing the power control amount in response to changes in the state of the power grid, the increase can be suppressed, while also being able to respond to cases where the increase in the power control amount is insufficient due to deviations from expectations.

[0105] According to at least one of the embodiments described above, by having a first-stage power control unit selection unit 30, a power control estimation model generation unit 40, a power control unit correction unit 50, a first-stage power control execution unit 60, a stability evaluation model generation unit 70, and an additional power control execution unit 80, it is possible to maintain a stable state of the power system even if the state of the power system changes significantly.

[0106] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0107] 1...power system, 2...bus, 3...transmission line, 4...transformer, 5...generator, 6...circuit breaker, 10...transmission system, 11...information terminal, 12...control terminal, 20...system stabilization device, 30...first-stage shearing control machine selection unit, 40...shearing control estimation model generation unit, 50...shearing control machine correction unit, 60...first-stage shearing control execution unit, 70...stability evaluation model generation unit, 80...additional shearing control execution unit

Claims

1. a selection unit that acquires system information representing the characteristics of a power system having a generator at a predetermined period, creates a system model that is a simulation model representing the power flow state of the power system using the system information, calculates transient stability in the event of a predetermined system fault occurring in the system model, and selects a first shearing control unit from among the generators to cut off the supply of power for each predetermined system fault based on the calculation result of the transient stability; a shearing control estimation model generation unit that generates a regression equation for predicting a shearing control machine from the system information based on shearing control machine information that is a combination of the system information and a first shearing control machine candidate for each of the predetermined system faults in the system model; a shearing control machine correction unit that calculates the shearing control amount necessary to maintain the stability of the power system using the regression equation, the system information last acquired by the selection unit, and the system information immediately before the occurrence of the predetermined system fault, and adds a new shearing control machine to the first shearing control machine or changes the first shearing control machine based on the calculated shearing control amount; a first-stage shear control execution unit that transmits a command to shut off the first shear control machine that has been added or changed by the shear control machine correction unit when a grid fault occurs; a stability evaluation model generation unit that prepares, from the results of the immediately preceding transient stability calculation, model definition information for determining the transition of the phase angle deviation used to determine whether or not a generator has lost synchronism from the measured values ​​of the power system and the generator before and after the occurrence of the fault, and a judgment criterion used to determine whether or not a generator has lost synchronism; an additional shear control execution unit that selects and shuts off an additional shear control machine when it is determined that a generator will lose synchronism after the occurrence of a fault based on a transition of a phase angle deviation calculated using the model definition information prepared by the stability evaluation model generation unit and the measured values ​​of the power system and a determination criterion; Equipped with Grid stabilizer.

2. The electrical control machine correction unit a control synchronous machine determination unit that calculates a control amount (A) required to maintain stability of the power system based on the regression equation and the system information immediately before the occurrence of the predetermined system fault, calculates a control amount (B) required to maintain stability of the power system based on the regression equation and the system information last acquired by the selection unit, and selects a control machine, with a synchronous generator as the target, to be added to or changed from the first control machine based on the magnitude relationship and difference between the control amount (A) and the control amount (B); a control renewable energy determination unit that calculates a power control amount necessary to maintain stability of the power system from the regression equation and the system information immediately before the occurrence of the predetermined system accident, and selects a power control machine for a renewable energy power source to be added to the first power control machine based on the power control amount shortage due to the output reduction of the first power control machine and the power control amount calculated by the regression equation; Equipped with The power system stabilization device according to claim 1.

3. The stability evaluation model generation unit an unstable generator model formulation unit that divides the generators of the power system into unstable generator groups and stable generator groups based on the transient stability calculation results, and compiles definition information for an unstable generator group model that converts the unstable generator groups into a single generator; a stable generator model formulation unit that compiles a function for calculating the total active power of the stable generators in the external system from the transient stability calculation results, and definition information for a stable generator group model that converts a stable generator group into a single generator; a criterion formulation unit that formulates a criterion for determining a phase angle deviation used for stability determination based on the transient stability calculation result; an output change model formulation unit that calculates, without performing transient stability calculations, the amount of change in active power converted into a one-machine infinite bus model that occurs when the first shearing machine is shut off, for all combinations that can become the first shearing machine, using information necessary for system calculations immediately before shearing that is obtained in the process of transient stability calculations; Equipped with The power system stabilization device according to claim 1 or 2.

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