System stabilization system
The power system stabilization system addresses grid frequency instability by dynamically adjusting load shedding based on power loss and frequency fluctuations, effectively preventing further frequency drops through a coordinated control mechanism.
Patent Information
- Application Number
- JP2024028400
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-02-28
- Publication Date
- 2025-09-09
AI Technical Summary
The increasing integration of renewable energy sources with fluctuating power output, such as solar power generation, exacerbates frequency drops in power grids due to insufficient control during power supply fluctuations, leading to potential grid instability.
A power system stabilization system comprising a power supply loss amount estimator, control target amount calculator, control object selector, start-up determination unit, control command output unit, and load shedding output unit, which dynamically adjusts load shedding based on system frequency and power loss to prevent further frequency drops.
The system effectively prevents further decreases in grid frequency by strategically shedding loads, ensuring stable power supply by initially reducing and gradually increasing the number of load lines cut off in response to power failures.
Smart Images
Figure 2025130975000001_ABST
Abstract
Description
[Technical Field]
[0001] An embodiment of the present invention relates to a power grid stabilization system. [Background technology]
[0002] Conventionally, when the system frequency of a power system drops due to the impact of a large-capacity generator tripping, a system stabilization device is known that restores the system frequency by controlling load lines that correspond to the power generation amount of the tripped generator. For example, when a generator trips, a conventional system stabilization device controls the system frequency to restore the system frequency by simultaneously shutting off preset control targets (load lines).
[0003] However, in recent years, the proportion of renewable energy sources such as solar power generation, which have large temporal output fluctuations, that are connected to the power grid has been increasing, and the amount of power generated can fluctuate in a short period of time due to the influence of weather, etc. For this reason, if the control amount becomes insufficient due to fluctuations in the power supply and demand situation, the drop in the grid frequency can become even more severe. [Prior art documents] [Non-patent literature]
[0004] [Non-Patent Document 1] "Frequency Relay System for Preventing Accident Spread," September 2008, Institute of Electrical Engineers of Japan Technical Report, No. 1127, p. 32 Summary of the Invention [Problem to be solved by the invention]
[0005] The problem to be solved by the present invention is to provide a grid stabilization system that can prevent the grid frequency from decreasing further. [Means for solving the problem]
[0006] A power system stabilization system according to an embodiment includes a power supply loss amount estimator, a control target amount calculator, a control object selector, a start-up determination unit, a control command output unit, and a load shedding output unit. The power supply loss amount estimator estimates a power supply loss amount in the event of a power supply loss accident in the power system based on power system information, which is information about the power system. The control target amount calculator calculates multiple control target amounts based on the power system information and the power supply loss amount estimated by the power supply loss amount estimator. The control object selector selects a control object for each of the multiple control target amounts calculated by the control target amount calculator. The start-up determination unit outputs start-up information in the event of a power supply loss accident. When the start-up information is output from the start-up determination unit, the control command output unit outputs a control command that is an instruction to control the control object for each of the multiple control target amounts selected by the control object selector. The load shedding output unit outputs a shutdown command to shut down the control object based on the control command output from the control command output unit when a system frequency of the power system is equal to or lower than a certain value. [Brief explanation of the drawings]
[0007] [Figure 1] 1 is a diagram showing the configuration of a power grid stabilization system 10 according to a first embodiment. [Figure 2] FIG. 2 is a block diagram for explaining the operation of the central processing unit 100 and the load control device 200 according to the first embodiment. [Figure 3] 4 is a diagram for explaining a control target selection process performed by a control target selection unit 140 according to the first embodiment. FIG. [Figure 4] FIG. 4 is a diagram showing an example of selection information 174 according to the first embodiment. [Figure 5] FIG. 3 is a diagram showing an example for explaining control timing according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing another example for explaining control timing according to the first embodiment. [Figure 7] FIG. 10 is a block diagram for explaining the operation of a central processing unit 100A and a load control device 200A according to the second embodiment. [Figure 8]FIG. 10 is a diagram showing an example for explaining control timing according to the second embodiment. [Figure 9] FIG. 10 is a block diagram for explaining the operation of a central processing unit 100B and a load control device 200B according to the third embodiment. [Figure 10] FIG. 10 is a diagram showing an example for explaining control timing according to the second embodiment. [Figure 11] FIG. 11 is a diagram showing an example for explaining control timing according to the third embodiment. [Figure 12] FIG. 10 is a block diagram for explaining the operation of a central processing unit 100C and a load control device 200C according to a fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION
[0008] Hereinafter, a power grid stabilization system according to an embodiment will be described with reference to the drawings.
[0009] (First embodiment) Fig. 1 is a diagram showing the configuration of a power grid stabilization system 10 according to the first embodiment. The power grid stabilization system 10 includes a central processing unit 100 and a load control device 200. The central processing unit 100 and the load control device 200 are capable of communicating with each other via a network NW. The network NW includes, for example, the Internet, a LAN (Local Area Network), a wireless base station, a provider device, and the like.
[0010] The central processing unit 100 is a computer that outputs a control command to the load control device 200 to control the load line when a power supply accident occurs in the power system. The central processing unit 100 is an example of a power system stabilization device.
[0011] The central processing unit 100 includes, for example, a communication unit 110, a power supply drop amount estimation unit 120, a control target amount calculation unit 130, a control target selection unit 140, a start-up determination unit 150, a control command output unit 160, and a storage unit 170. The components other than the communication unit 110 and the storage unit 170 are realized by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). 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.
[0012] The storage unit 170 is a HDD, a flash memory, a RAM (Random Access Memory), etc. The storage unit 170 may be a NAS (Network Attached Storage) device that can be accessed by the central processing unit 100 via the network NW. The storage unit 170 stores information such as system information 172 and selection information 174.
[0013] The communication unit 110 is a communication interface for connecting to the network NW, and is, for example, a network interface card.
[0014] The load control device 200 is a computer that controls a load line based on a control command output from the central processing unit 100. The load control device 200 includes, for example, a communication unit 210, an under-frequency relay 220, a load shedding output unit 230, and a power flow measurement unit 240. The load shedding output unit 230 is implemented, for example, by a hardware processor such as a CPU executing a program (software). Some or all of these components may be implemented by hardware such as an LSI, ASIC, FPGA, or GPU, or by a combination of software and hardware. The program may be stored in advance in a storage device such as a hard disk drive (HDD) or flash memory (a storage device having 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. Although FIG. 1 shows only one load control device 200 connected to the central processing unit 100 via a network NW, multiple load control devices 200 may be used.
[0015] The under frequency relay 220 is a device for detecting that the system frequency of the power system has dropped to a predetermined value. The system frequency may be, for example, the frequency of the voltage of the power system or the frequency of the current of the power system. When the under frequency relay 220 detects that the system frequency of the power system has dropped to a predetermined value, the load shedding output unit 230 outputs a shedding command to a predetermined load line to shedding the load line. This makes it possible to prevent the system frequency from dropping further. Note that although three load lines are shown in FIG. 2, it is assumed that more load lines actually exist.
[0016] When the load shedding output unit 230 receives a control command from the central processing unit 100 in response to a power supply tripping accident occurring in the power system, it outputs a shutoff command to the load line specified by the control command to shut off the load line. This makes it possible to prevent the system frequency from decreasing further when a power supply tripping accident occurs in the power system.
[0017] The power flow measurement unit 240 acquires currents and voltages from the load lines and measures the active power values of each load line. For example, the power flow measurement unit 240 may calculate the active power value of each load line by multiplying the current and voltage acquired from each load line. The power flow measurement unit 240 also outputs the calculated active power value of each load line to the central processing unit 100. The active power value of each load line is used in the control target selection process by the control target selection unit 140, as will be described later.
[0018] The communication unit 210 is a communication interface for connecting to the network NW, and is, for example, a network interface card.
[0019] Fig. 2 is a block diagram for explaining the operation of the central processing unit 100 and the load control device 200 of the first embodiment. As shown in Fig. 2, system information 172 is input to the central processing unit 100. The system information 172 is information about the power system, and includes, for example, the active power value of each generator and device identification information (generator ID, etc.).
[0020] The power failure amount estimation unit 120 estimates the amount of power failure when a power failure accident occurs in the power system, based on the system information 172 input to the central processing unit 100. Specifically, the power failure amount estimation unit 120 acquires the active power value of each generator that is to be monitored for power failure in the power system, based on the system information 172, and estimates the amount of power failure when each generator trips, based on the acquired active power value. For example, if the active power value of generator A is 100 MW, the amount of power failure when generator A trips is estimated to be 100 MW.
[0021] The control target amount calculation unit 130 calculates a plurality of control target amounts based on the system information 172 and the amount of power supply loss estimated by the power supply loss amount estimation unit 120. In this embodiment, the control target amount calculation unit 130 calculates three control target amounts for the first to third stages by multiplying the amount of power supply loss by a plurality of different percentages (for example, 90%, 100%, 110%).
[0022] Specifically, when the amount of power source loss when generator A trips is 100 MW, the control target amount calculation unit 130 calculates three control target amounts for the first to third stages based on the following formulas: Note that the control target amount calculation unit 130 calculates multiple control target amounts for all generators that are targets of monitoring for power source loss in the power system included in the system information 172.
[0023] Control target amount (1st stage) < Control target amount (2nd stage) < Control target amount (3rd stage) Control target amount (first stage) = 100MW x 90% = 90MW Control target amount (second stage) = 100MW x 100% = 100MW Control target amount (third stage) = 100MW x 110% = 110MW
[0024] The control target selection unit 140 selects a control target for each of the three control target amounts of the first to third stages calculated by the control target amount calculation unit 130. This point will be described with reference to FIG.
[0025] 3 is a diagram for explaining the selection process of a control target by the control target selection unit 140 of the first embodiment. The table shown in Fig. 3 shows the control targets (load lines), the control amount for each load line, the first-stage control target, the second-stage control target, and the third-stage control target. The control amount (active power value) of each load line is information acquired from the load control device 200.
[0026] 3, since the control target amount (first stage) is 90 MW, the control target selection unit 140 selects load lines of 90 MW as the control targets of the first stage. Specifically, the control target selection unit 140 selects load line 1 and load line 2 as the control targets of the first stage. Since the control amount of load line 1 is 50 MW and the control amount of load line 2 is 40 MW, the total value of these control amounts is 90 MW, which matches the control target amount (first stage).
[0027] Furthermore, since the control target amount (second stage) is 100 MW, the control target selection unit 140 selects load lines for 100 MW, including the control targets of the first stage, as control targets of the second stage. Specifically, the control target selection unit 140 selects load line 3 in addition to load line 1 and load line 2, which are control targets of the first stage, as control targets of the second stage. The control amount of load line 1 is 50 MW, the control amount of load line 2 is 40 MW, and the control amount of load line 3 is 10 MW, so the total value of these control amounts is 100 MW, which matches the control target amount (second stage).
[0028] Furthermore, since the control target amount (third stage) is 110 MW, the control target selection unit 140 selects load lines for 110 MW, including the control targets of the second stage, as control targets of the third stage. Specifically, the control target selection unit 140 selects load line 4 in addition to load line 1, load line 2, and load line 3, which are control targets of the second stage, as control targets of the third stage. The control amount of load line 1 is 50 MW, the control amount of load line 2 is 40 MW, the control amount of load line 3 is 10 MW, and the control amount of load line 4 is 10 MW, so the total value of these control amounts is 110 MW, which matches the control target amount (third stage).
[0029] Fig. 4 is a diagram showing an example of the selection information 174 according to the first embodiment. The control target selection unit 140 generates the selection information 174 by performing the control target selection process described in Fig. 3 on all power generators that are to be monitored for power supply loss in the power grid.
[0030] The selection information 174 includes, for example, a generator ID, a first-stage control target, a second-stage control target, and a third-stage control target. The generator ID is identification information for identifying a generator included in the power system. The first-stage to third-stage control targets are information indicating the load lines selected by the control target selection unit 140. The control target selection unit 140 stores the generated selection information 174 in the storage unit 170.
[0031] Returning to the explanation of Fig. 2, when a power supply failure accident occurs in the power system, accident information 173 is input to the central processing unit 100. The accident information 173 is information including the generator ID of the generator in which the accident occurred, and may also include other information such as the details of the accident. The start-up determination unit 150 determines that a power supply failure accident has occurred in the power system based on the accident information 173 input to the central processing unit 100.
[0032] Furthermore, the activation determination unit 150 outputs activation information for activating the load shedding function of the load control device 200 to the control command output unit 160 based on the accident information 173. The load shedding function is a function for cutting off the current flowing through each load line by controlling a circuit breaker provided on each load line. The activation information includes the generator ID of the generator in which the power supply tripping accident occurred.
[0033] When activation information is output from activation determination unit 150, control command output unit 160 outputs a plurality of control commands, which are instructions for controlling the control targets selected by control target selection unit 140, to load control device 200. Specifically, control command output unit 160 acquires the first to third stage control targets corresponding to the generator ID included in the activation information from selection information 174 stored in storage unit 170. Furthermore, control target selection unit 140 outputs the first to third stage control targets acquired from selection information 174 to control command output unit 160. In this way, control command output unit 160 can acquire the first to third stage control targets corresponding to the generator in which a power supply tripping accident has occurred.
[0034] Next, the control command output unit 160 outputs a control command (first stage) to the load control device 200 to cause the first stage control object (load line) to be cut off. The load shedding output unit 230 of the load control device 200 causes the first stage control object (load line) to be cut off based on the control command (first stage) output from the control command output unit 160. For example, in the example shown in Fig. 4, load line 1 and load line 2 are cut off.
[0035] Next, the control command output unit 160 uses the first timer T1 to wait until a certain time has elapsed since outputting the control command (first stage) to the load control device 200. Thereafter, the control command output unit 160 outputs a control command (second stage) to the load control device 200 to cause the control object (load line) of the second stage to be cut off. The load shedding output unit 230 of the load control device 200 causes the control object (load line) of the second stage to be cut off based on the control command (second stage) output from the control command output unit 160. For example, in the example shown in FIG. 4, load lines 1 to 3 are cut off.
[0036] Next, the control command output unit 160 uses the second timer T2 to wait until a certain time has elapsed since outputting the control command (second stage) to the load control device 200. Thereafter, the control command output unit 160 outputs a control command (third stage) to the load control device 200 to cut off the control object (load line) in the third stage. Based on the control command (third stage) output from the control command output unit 160, the load shedding output unit 230 of the load control device 200 cuts off the control object (load line) in the third stage when the frequency down relay 220 is operating. For example, in the example shown in FIG. 4, load lines 1 to 4 are cut off.
[0037] 4, if a power failure occurs in the generator with generator ID 0001, load lines 1 and 2 are cut off as first-stage control, and after a certain time, load line 3 is additionally cut off as second-stage control, and after a further certain time, load line 4 is additionally cut off as third-stage control. This makes it possible to prevent the system frequency from decreasing further even if a power failure occurs in the power system.
[0038] Fig. 5 is a diagram illustrating an example of control timing according to the first embodiment. As shown in Fig. 5, when a power supply accident occurs in the power grid and the system frequency drops, the control command output unit 160 outputs a control command (first stage) to the load control device 200 at time t1. This causes the controlled object (load line) of the first stage to be cut off.
[0039] After a certain time T1 has elapsed since the control command (first stage) was output to the load control device 200, the control command output unit 160 outputs a control command (second stage) at time t2 to the load control device 200. As a result, the controlled object (load line) of the second stage is cut off.
[0040] After a certain time T2 has elapsed since the control command (second stage) was output to the load control device 200, the control command output unit 160 outputs a control command (third stage) to the load control device 200 at time t3. This causes the controlled object (load line) of the third stage to be cut off. In the example shown in Fig. 5, the system frequency is restored after the controlled object of the third stage is cut off.
[0041] Fig. 6 is a diagram showing another example for explaining the control timing of the first embodiment. As shown in Fig. 6, when a power supply accident occurs in the power grid and the system frequency drops, the control command output unit 160 outputs a control command (first stage) to the load control device 200 at time t1. This causes the controlled object (load line) of the first stage to be cut off.
[0042] After outputting the control command (first stage) to the load control device 200, the control command output unit 160 outputs a control command (second stage) to the load control device 200 at time t2. This causes the controlled object (load line) of the second stage to be cut off. In the example shown in Fig. 6, after the controlled object of the second stage is cut off, the system frequency is recovered.
[0043] After a certain time T2 has elapsed since the control command (second stage) was output to the load control device 200, the control command output unit 160 outputs a control command (third stage) to the load control device 200 at time t3. However, since the system frequency has recovered, the load shedding output unit 230 of the load control device 200 does not shedding the controlled object (load line) of the third stage. This makes it possible to prevent more load lines than necessary from being shedding.
[0044] The load shedding output unit 230 determines whether the grid frequency is falling using the under frequency relay 220. In practice, the load control device 200 is provided with the under frequency relay 220, and the load shedding output unit 230 outputs a shedding signal when the under frequency relay 220 is operating.
[0045] In this way, by initially reducing the number of load lines to be cut off and gradually increasing the number of load lines to be cut off while monitoring the system frequency, it is possible to prevent more load lines than necessary from being cut off.
[0046] As described above, the power grid stabilization system 10 of this embodiment includes a power grid failure amount estimation unit 120, a control target amount calculation unit 130, a control target selection unit 140, an activation determination unit 150, a control command output unit 160, and a load shedding output unit 230. The power grid failure amount estimation unit 120 estimates the amount of power failure when a power grid failure occurs, based on power grid information 172, which is information about the power grid. The control target amount calculation unit 130 calculates multiple control target amounts based on the power grid information 172 and the amount of power failure estimated by the power grid failure amount estimation unit 120. The control target selection unit 140 selects a control target for each of the multiple control target amounts calculated by the control target amount calculation unit 130. The activation determination unit 150 outputs activation information when a power grid failure occurs. The control command output unit 160 outputs a control command, which is an instruction to control the control target for each of the multiple control target amounts selected by the control target selection unit 140, when the activation determination unit 150 outputs the activation information. When the system frequency of the power system is equal to or lower than a certain value, the load shedding output unit 230 outputs a shedding command to shedding the controlled object based on the control command output from the control command output unit 160. This allows the power system stabilization system 10 of this embodiment to prevent the system frequency from decreasing further.
[0047] Furthermore, the control target amount calculation unit 130 calculates a plurality of control target amounts by multiplying the amount of power source dropout by a plurality of different ratios (for example, 90%, 100%, 110%). This allows the power grid stabilization system 10 of this embodiment to easily calculate a plurality of control target amounts.
[0048] (Second embodiment) In the first embodiment described above, the control command output unit 160 outputs the control commands for the first to third stages using the first timer T1 and the second timer T2. In contrast, in the second embodiment, the first to third stage frequency down relays are separately provided, and the control commands for the first to third stages are output at timings based on the detection results of the first to third stage frequency down relays. The second embodiment will be described in detail below.
[0049] 7 is a block diagram for explaining the operation of the central processing unit 100A and the load control device 200A of the second embodiment. In FIG. 7, the processing contents of the power supply drop amount estimation unit 120, the control target amount calculation unit 130, and the control target selection unit 140 are the same as those in the first embodiment, so the description thereof will be omitted.
[0050] First-stage under-frequency relay 300-1 is a device for detecting that the system frequency of the power system has dropped to f1. Second-stage under-frequency relay 300-2 is a device for detecting that the system frequency of the power system has dropped to f2. Third-stage under-frequency relay 300-3 is a device for detecting that the system frequency of the power system has dropped to f3. Note that first-stage under-frequency relay 300-1, second-stage under-frequency relay 300-2, and third-stage under-frequency relay 300-3 are devices different from under-frequency relay 220 in load control device 200A.
[0051] When a power supply failure accident occurs in the power system, accident information 173 is input to the central processing unit 100A. The accident information 173 is information including the generator ID of the generator in which the accident occurred, and may also include other information such as the details of the accident. The start-up determination unit 150 determines that a power supply failure accident has occurred in the power system based on the accident information 173 input to the central processing unit 100A.
[0052] Furthermore, after a power supply accident occurs in the power system, when the first-stage frequency reduction relay 300-1 detects that the system frequency of the power system has dropped to f1, the activation determination unit 150 outputs first-stage activation information to the control command output unit 160. The first-stage activation information is information for activating the first-stage load shedding function of the load control device 200A, and includes the generator ID of the generator in which the power supply accident occurred.
[0053] When the activation information of the first stage is output from the activation determination unit 150, the control command output unit 160 outputs a first-stage control command, which is an instruction to control the first-stage control object selected by the control object selection unit 140, to the load control device 200A. Specifically, the control command output unit 160 acquires the first-stage control object corresponding to the generator ID included in the activation information from the selection information 174 stored in the storage unit 170. Furthermore, the control object selection unit 140 outputs the first-stage control object acquired from the selection information 174 to the control command output unit 160. In this way, the control command output unit 160 can acquire the first-stage control object corresponding to the generator in which the power supply tripping accident has occurred.
[0054] Next, the control command output unit 160 outputs a control command (first stage) to the load control device 200A to cause the first stage control object (load line) to be cut off. The load shedding output unit 230 of the load control device 200A causes the first stage control object (load line) to be cut off based on the control command (first stage) output from the control command output unit 160. For example, in the example shown in Fig. 4, load line 1 and load line 2 are cut off.
[0055] Furthermore, after a power supply accident occurs in the power system, when the second-stage frequency reduction relay 300-2 detects that the system frequency of the power system has dropped to f2, the activation determination unit 150 outputs second-stage activation information to the control command output unit 160. The second-stage activation information is information for activating the second-stage load shedding function of the load control device 200A, and includes the generator ID of the generator in which the power supply accident occurred.
[0056] When second-stage activation information is output from the activation determination unit 150, the control command output unit 160 outputs a second-stage control command, which is an instruction to control the second-stage control object selected by the control object selection unit 140, to the load control device 200A. Specifically, the control command output unit 160 acquires the second-stage control object corresponding to the generator ID included in the activation information from the selection information 174 stored in the storage unit 170. Furthermore, the control object selection unit 140 outputs the second-stage control object acquired from the selection information 174 to the control command output unit 160. In this way, the control command output unit 160 can acquire the second-stage control object corresponding to the generator in which the power supply tripping accident occurred.
[0057] Next, the control command output unit 160 outputs a control command (second stage) to the load control device 200A to cause the second stage control object (load line) to be cut off. The load shedding output unit 230 of the load control device 200A causes the second stage control object (load line) to be cut off based on the control command (second stage) output from the control command output unit 160. For example, in the example shown in Fig. 4, load lines 1 to 3 are cut off.
[0058] Furthermore, after a power supply accident occurs in the power system, when the third-stage frequency reduction relay 300-3 detects that the system frequency of the power system has dropped to f3, the activation determination unit 150 outputs third-stage activation information to the control command output unit 160. The third-stage activation information is information for activating the third-stage load shedding function of the load control device 200A, and includes the generator ID of the generator in which the power supply accident occurred.
[0059] When the activation information of the third stage is output from the activation determination unit 150, the control command output unit 160 outputs a third-stage control command, which is an instruction to control the control object of the third stage selected by the control object selection unit 140, to the load control device 200A. Specifically, the control command output unit 160 acquires the control object of the third stage corresponding to the generator ID included in the activation information from the selection information 174 stored in the storage unit 170. Furthermore, the control object selection unit 140 outputs the control object of the third stage acquired from the selection information 174 to the control command output unit 160. In this way, the control command output unit 160 can acquire the control object of the third stage corresponding to the generator in which the power supply tripping accident occurred.
[0060] Next, the control command output unit 160 outputs a control command (third stage) to the load control device 200A to cause the third stage control object (load line) to be cut off. The load shedding output unit 230 of the load control device 200A causes the third stage control object (load line) to be cut off based on the control command (third stage) output from the control command output unit 160. For example, in the example shown in Fig. 4, load lines 1 to 4 are cut off.
[0061] Fig. 8 is a diagram illustrating an example of control timing according to the second embodiment. As shown in Fig. 8, when the first-stage frequency down relay 300-1 detects that the grid frequency has dropped to f1, the control command output unit 160 outputs a control command (first stage) to the load control device 200A at time t1. This causes the controlled object (load line) of the first stage to be cut off.
[0062] After the control command (first stage) is output to the load control device 200A, when the frequency down relay 300-2 of the second stage detects that the grid frequency has dropped to f2, the control command output unit 160 outputs a control command (second stage) to the load control device 200A at time t2. This causes the controlled object (load line) of the second stage to be cut off.
[0063] After the control command (second stage) is output to the load control device 200A, when the frequency down relay 300-3 of the third stage detects that the grid frequency has dropped to f3, the control command output unit 160 outputs a control command (third stage) to the load control device 200A at time t3. This causes the controlled object of the third stage (load line) to be cut off. In the example shown in FIG. 8, the grid frequency recovers after the controlled object of the third stage is cut off.
[0064] As described above, the activation determination unit 150 of this embodiment outputs activation information according to the degree of decrease in the grid frequency, and the control command output unit 160 outputs a control command to a control target corresponding to the degree of decrease in the grid frequency among the control targets for each of the multiple control target quantities every time activation information is output from the activation determination unit 150. In this way, by initially reducing the number of load lines to be cut off and gradually increasing the number of load lines to be cut off while monitoring the grid frequency, the central processing unit 100A (grid system stabilization device) of this embodiment can prevent more load lines than necessary from being cut off.
[0065] (Third embodiment) In the first embodiment described above, the control command output unit 160 outputs control commands for the first to third stages using the first timer T1 and the second timer T2. In contrast, in the third embodiment, the control command output unit 160 outputs control commands for the first to third stages simultaneously, and the load shedding output unit 230 shedding the load line at a timing based on the detection results of the frequency undercut relays for the first to third stages provided in the load control device 200B. The third embodiment will be described in detail below.
[0066] 9 is a block diagram for explaining the operation of the central processing unit 100B and the load control device 200B of the third embodiment. In FIG. 9, the processing contents of the power supply drop amount estimation unit 120, the control target amount calculation unit 130, and the control target selection unit 140 are the same as those in the first embodiment, so the description thereof will be omitted.
[0067] When a power supply failure accident occurs in the power system, accident information 173 is input to the central processing unit 100B. The accident information 173 is information including the generator ID of the generator in which the accident occurred, and may also include other information such as the details of the accident. The start-up determination unit 150 determines that a power supply failure accident has occurred in the power system based on the accident information 173 input to the central processing unit 100B.
[0068] Furthermore, the activation determination unit 150 outputs activation information for activating the load shedding function of the load control device 200B to the control command output unit 160 based on the accident information 173. The activation information includes the generator ID of the generator in which the power supply loss accident occurred.
[0069] When activation information is output from activation determination unit 150, control command output unit 160 outputs a plurality of control commands, which are instructions for controlling the control targets selected by control target selection unit 140, to load control device 200B. Specifically, control command output unit 160 acquires the first to third stage control targets corresponding to the generator ID included in the activation information from selection information 174 stored in storage unit 170. Furthermore, control target selection unit 140 outputs the first to third stage control targets acquired from selection information 174 to control command output unit 160. In this way, control command output unit 160 can acquire the first to third stage control targets corresponding to the generator in which a power supply tripping accident has occurred.
[0070] Next, the control command output unit 160 simultaneously outputs to the load control device 200B a control command (first stage) for disconnecting the first stage control object (load line), a control command (second stage) for disconnecting the second stage control object (load line), and a control command (third stage) for disconnecting the third stage control object (load line).
[0071] Load control device 200B includes first-stage under-frequency relay 220-1, second-stage under-frequency relay 220-2, and third-stage under-frequency relay 220-3. First-stage under-frequency relay 220-1 is a device for detecting that the system frequency of the power system has dropped to f1. Second-stage under-frequency relay 220-2 is a device for detecting that the system frequency of the power system has dropped to f2. Third-stage under-frequency relay 220-3 is a device for detecting that the system frequency of the power system has dropped to f3.
[0072] When the first-stage frequency down relay 220-1 detects that the system frequency of the power system has dropped to f1, the load shedding output unit 230 sheddings the control target (load line) of the first stage based on the control command (first stage) output from the control command output unit 160. For example, in the example shown in Fig. 4, load line 1 and load line 2 are shedding.
[0073] Furthermore, when the second-stage frequency reduction relay 220-2 detects that the system frequency of the power system has dropped to f2, the load shedding output unit 230 sheddings the second-stage control target (load line) based on the control command (second stage) output from the control command output unit 160. For example, in the example shown in Fig. 4, load lines 1 to 3 are shedding.
[0074] Furthermore, when the third-stage frequency reduction relay 220-3 detects that the system frequency of the power system has dropped to f3, the load shedding output unit 230 sheddings the control target (load line) of the third stage based on the control command (third stage) output from the control command output unit 160. For example, in the example shown in Fig. 4, load lines 1 to 4 are shedding.
[0075] Fig. 10 is a diagram showing an example for explaining the control timing of the second embodiment, and Fig. 11 is a diagram showing an example for explaining the control timing of the third embodiment. The difference in control timing between the second embodiment and the third embodiment will be explained using Fig. 10 and Fig. 11.
[0076] 10, in the second embodiment, when the first-stage frequency down relay 300-1 detects that the grid frequency has dropped to f1 at time t1, the control command output unit 160 of the central processing unit 100A outputs a control command (first stage) to the load control device 200A. Furthermore, the load shedding output unit 230 of the load control device 200A shedding the controlled object (load line) of the first stage based on the control command (first stage) output from the control command output unit 160.
[0077] After the control command (first stage) is output to the load control device 200A, when the frequency down relay 300-2 of the second stage detects that the grid frequency has dropped to f2 at time t2, the control command output unit 160 of the central processing unit 100A outputs a control command (second stage) to the load control device 200A. Furthermore, the load shedding output unit 230 of the load control device 200A shedding the controlled object (load line) of the second stage based on the control command (second stage) output from the control command output unit 160.
[0078] After the control command (second stage) is output to the load control device 200A, when the frequency down relay 300-3 of the third stage detects that the grid frequency has dropped to f3 at time t3, the control command output unit 160 of the central processing unit 100A outputs a control command (third stage) to the load control device 200A. Furthermore, the load shedding output unit 230 of the load control device 200A shedding the controlled object (load line) of the third stage based on the control command (third stage) output from the control command output unit 160.
[0079] On the other hand, as shown in FIG. 11, in the third embodiment, the control command output unit 160 outputs the control commands for the first to third stages simultaneously to the load control device 200B.
[0080] When the first-stage frequency reduction relay 220-1 detects that the system frequency has dropped to f1 at time t1, the load shedding output unit 230 of the load control device 200B sheddings the controlled object (load line) of the first stage based on the control command (first stage) output from the control command output unit 160.
[0081] In addition, when the second-stage frequency reduction relay 220-2 detects that the system frequency has dropped to f2 at time t2, the load shedding output unit 230 sheddings the controlled object (load line) of the second stage based on the control command (second stage) output from the control command output unit 160.
[0082] In addition, when the third-stage frequency reduction relay 220-3 detects that the system frequency has dropped to f3 at time t3, the load shedding output unit 230 sheddings the controlled object (load line) of the third stage based on the control command (third stage) output from the control command output unit 160.
[0083] In the second embodiment, the control command is output after the grid frequency has dropped to a predetermined value, which delays the timing of disconnecting the controlled object (load line). In contrast, in the third embodiment, the control command output unit 160 simultaneously outputs first- to third-stage control commands to the load control device 200B in advance, and when the frequency reduction relay in the load control device 200B detects that the grid frequency has dropped to a predetermined value, the controlled object (load line) can be immediately disconnected. Therefore, the third embodiment can disconnect the controlled object (load line) earlier than the second embodiment, and can more quickly prevent the grid frequency from dropping.
[0084] As described above, the control command output unit 160 of this embodiment simultaneously outputs a plurality of control commands according to the degree of decrease in the grid frequency, thereby causing the load control device 200B that receives the plurality of control commands to sequentially shut off control targets according to the degree of decrease in the grid frequency. This allows the central processing unit 100B (grid stabilization device) of this embodiment to more quickly prevent the decrease in the grid frequency from progressing.
[0085] (Fourth embodiment) In the first to third embodiments described above, the control target amount calculation unit 130 calculates a plurality of control target amounts based on the system information 172 and the amount of power supply dropout estimated by the power supply dropout amount estimation unit 120. In contrast, in the fourth embodiment, the ex-post control target amount calculation unit 190 recalculates the control target amount to a more appropriate value in accordance with a change in the system frequency. The fourth embodiment will be described in detail below.
[0086] FIG. 12 is a block diagram illustrating the operation of a central processing unit 100C and a load control device 200C according to the fourth embodiment. As shown in FIG. 12, the central processing unit 100C includes a frequency change detection unit 180 and a post-control target amount calculation unit 190. The frequency change detection unit 180 and the post-control target amount calculation unit 190 are implemented, for example, by a hardware processor such as a CPU executing a program (software). Some or all of these components may be implemented by hardware such as an LSI, ASIC, FPGA, or GPU, or may be implemented by a combination of software and hardware. The program may be stored in advance in a storage device such as an HDD or flash memory (a storage device having 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.
[0087] 12, the central processing unit 100C receives system information 172. The system information 172 is information about the power system, and includes, for example, the active power value of each generator and device identification information (generator ID, etc.).
[0088] The power supply failure amount estimation unit 120 estimates the amount of power failure in the event of a power failure accident in the power system, based on the system information 172 input to the central processing unit 100C. Specifically, the power supply failure amount estimation unit 120 acquires the active power value of each generator that is to be monitored for power failure in the power system, based on the system information 172, and estimates the amount of power failure in the event of each generator tripping, based on the acquired active power value.
[0089] The control target amount calculation unit 130 calculates the control target amount based on the system information 172 and the amount of power supply loss estimated by the power supply loss amount estimation unit 120. For example, if the amount of power supply loss when generator A trips is 100 MW, the control target amount calculation unit 130 calculates the control target amount to be 100 MW.
[0090] The control target selection unit 140 selects a control target in accordance with the control target amount calculated by the control target amount calculation unit 130. The control target selection process has been described using Figures 3 and 4, and therefore a description thereof will be omitted. In this embodiment, since only one control target amount is calculated by the control target amount calculation unit 130, the control target selected by the control target selection unit 140 is one pattern only.
[0091] On the other hand, when a power supply failure accident occurs in the power system, accident information 173 is input to the central processing unit 100C. The accident information 173 is information including the generator ID of the generator in which the accident occurred, and may also include other information such as the details of the accident. The start-up determination unit 150 determines that a power supply failure accident has occurred in the power system based on the accident information 173 input to the central processing unit 100C.
[0092] Furthermore, the activation determination unit 150 outputs activation information for activating the load shedding function of the load control device 200C to the control command output unit 160 based on the accident information 173. The activation information includes the generator ID of the generator in which the power supply loss accident occurred.
[0093] When the activation information is output from the activation determination unit 150, the control command output unit 160 outputs a control command, which is an instruction to control the control target selected by the control target selection unit 140, to the load control device 200C. Specifically, the control command output unit 160 acquires the control target associated with the generator ID included in the activation information from the selection information 174 stored in the storage unit 170. Furthermore, the control target selection unit 140 outputs the control target acquired from the selection information 174 to the control command output unit 160. In this way, the control command output unit 160 can acquire the control target corresponding to the generator in which the power supply tripping accident occurred.
[0094] Next, the control command output unit 160 outputs a control command to the load control device 200C to cause the controlled object (load line) to be cut off. The load shedding output unit 230 of the load control device 200C causes the controlled object (load line) to be cut off based on the control command output from the control command output unit 160.
[0095] On the other hand, the control command output unit 160 outputs an output notification to the ex-post control target amount calculation unit 190 to notify that a control command has been output to the load control device 200C.
[0096] The frequency change detection unit 180 acquires the system frequency 175 and detects a change in the system frequency 175 after the control of the controlled object. The post-control target amount calculation unit 190 acquires the change in the system frequency 175 detected by the frequency change detection unit 180 when a predetermined time has elapsed since the output notification was output from the control command output unit 160. Then, the post-control target amount calculation unit 190 recalculates the control target amount based on the change in the system frequency 175 detected by the frequency change detection unit 180.
[0097] For example, when the grid frequency 175 has dropped below a preset threshold, the post-control target amount calculation unit 190 may recalculate the control target amount to a larger value. For example, when the control target amount is 100 MW, the control target amount may be recalculated by multiplying it by a predetermined rate (for example, 110%). On the other hand, when the grid frequency 175 has not dropped below the preset threshold, the post-control target amount calculation unit 190 may recalculate the control target amount to a smaller value. For example, when the control target amount is 100 MW, the control target amount may be recalculated by multiplying it by a predetermined rate (for example, 90%).
[0098] The control target selection unit 140 reselects the control target in accordance with the control target amount recalculated by the post-control target amount calculation unit 190. Furthermore, the control command output unit 160 outputs a control command to the load control device 200C to cause the reselected control target (load line) to be shedding. The load shedding output unit 230 of the load control device 200C shedding the control target (load line) based on the control command output from the control command output unit 160.
[0099] As described above, the power grid stabilization system 10 of this embodiment includes the power grid loss amount estimator 120, the control target amount calculator 130, the controlled object selector 140, the activation determination unit 150, the control command output unit 160, the load shedding output unit 230, the frequency change detector 180, and the ex-post control target amount calculator 190. The power grid loss amount estimator 120 estimates the amount of power loss when a power grid loss accident occurs, based on power grid information 172, which is information about the power grid. The control target amount calculator 130 calculates the control target amount based on the power grid information 172 and the amount of power loss estimated by the power grid loss amount estimator 120. The controlled object selector 140 selects a controlled object based on the control target amount calculated by the control target amount calculator 130. The activation determination unit 150 outputs activation information when a power grid loss accident occurs. When activation information is output from the activation determination unit 150, the control command output unit 160 outputs a control command that is an instruction to control the control object selected by the control object selection unit 140. When the system frequency of the power system is equal to or lower than a certain value, the load shedding output unit 230 outputs a shutdown command to shut down the control object based on the control command output from the control command output unit 160. The frequency change detection unit 180 detects a change in the system frequency after the control of the control object. The post-control target amount calculation unit 190 recalculates the control target amount based on the change in the system frequency detected by the frequency change detection unit 180. In this way, the power system stabilization system 10 of this embodiment can prevent the system frequency from decreasing further.
[0100] 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]
[0101] 10... Power system stabilization system, 100, 100A, 100B, 100C... Central processing unit, 110... Communication unit, 120... Power supply loss amount estimation unit, 130... Control target amount calculation unit, 140... Control target selection unit, 150... Start-up determination unit, 160... Control command output unit, 170... Memory unit, 172... Power system information, 173... Fault information, 174... Selection information, 175... Power system frequency, 180... Frequency change detection unit, 180, 190... Post-control target amount calculation unit, 200, 200A, 200B, 200C... Load control device, 210... Communication unit, 220... Frequency under-relay, 230... Load shedding output unit, 240... Power flow measurement unit
Claims
1. a power loss amount estimation unit that estimates an amount of power loss when a power loss accident occurs in the power system based on system information that is information about the power system; a control target amount calculation unit that calculates a plurality of control target amounts based on the system information and the amount of power supply loss estimated by the power supply loss amount estimation unit; a control target selection unit that selects a control target for each of the plurality of control target amounts calculated by the control target amount calculation unit; a start-up determination unit that outputs start-up information when the power supply failure accident occurs; a control command output unit that outputs, when the activation information is output from the activation determination unit, a control command that is an instruction to control the control object for each of the plurality of control target amounts selected by the control object selection unit; and a load shedding output unit that outputs a shedding command to shedding the controlled object based on the control command output from the control command output unit when a system frequency of the power system is equal to or lower than a certain value; A grid stabilization system equipped with:
2. the control target amount calculation unit calculates the plurality of control target amounts by multiplying the amount of power supply dropout by a plurality of ratios that are different from one another. The power grid stabilization system according to claim 1 .
3. the activation determination unit outputs the activation information according to a degree of decrease in the grid frequency; the control command output unit outputs the control command to a control target corresponding to a degree of decrease in the grid frequency among the control targets for the plurality of control target amounts every time the start-up information is output from the start-up determination unit. The power grid stabilization system according to claim 1 .
4. the control command output unit simultaneously outputs a plurality of control commands according to the degree of decrease in the grid frequency, thereby causing the devices that have received the plurality of control commands to sequentially shut off the control targets according to the degree of decrease in the grid frequency; The power grid stabilization system according to claim 1 .
5. a power loss amount estimation unit that estimates an amount of power loss when a power loss accident occurs in the power system based on system information that is information about the power system; a control target amount calculation unit that calculates a control target amount based on the system information and the amount of power supply loss estimated by the power supply loss amount estimation unit; a control target selection unit that selects a control target based on the control target amount calculated by the control target amount calculation unit; a start-up determination unit that outputs start-up information when the power supply failure accident occurs; a control command output unit that outputs a control command that is an instruction to control the control object selected by the control object selection unit when the activation information is output from the activation determination unit; a load shedding output unit that outputs a shedding command to shedding the controlled object based on the control command output from the control command output unit when a system frequency of the power system is equal to or lower than a certain value; a frequency change detection unit that detects a change in the system frequency after the controlled object is controlled; a post-control target amount calculation unit that recalculates the control target amount based on the change in the system frequency detected by the frequency change detection unit; and A grid stabilization system equipped with: