Power system stabilization system, computer program for power system stabilization system, and power system stabilization method

Abstract

To provide a power system stabilization system, a computer program for a power system stabilization system, and a power system stabilization method, for avoiding excessive power control during an N-4 accident.SOLUTION: In a central processing unit 1 configured to acquire system information at a constant cycle and to determine a power control target for each assumed accident, an N-2 accident countermeasure determination unit 110 includes: an N-2 stability calculation unit 112 configured to calculate stability of a power system P in each of a plurality of N-2 assumed accidents and to determine a power control target for each N-2 assumed accident; and an N-2 control table creation unit 113 configured to create an N-2 control table by associating the power control target for each N-2 assumed accident with the N-2 assumed accident. An N-4 accident countermeasure determination unit 120 includes an N-4 stability calculation unit 122 configured to calculate stability of the power system P in an N-4 assumed accident and to determines a power control target for each N-4 assumed accident. The N-4 stability calculation unit 122 inherits contents of the N-2 control table created by the N-2 control table creation unit 113 and to perform stability calculation.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present embodiment relates to a power system stabilization system, a computer program for the power system stabilization system, and a power system stabilization method for maintaining the stability of the power system and supplying electric power stably even when an accident occurs in the power system. [Background technology]

[0002] In a power system, many generators operate in sync with each other to supply power. If a severe accident occurs in the power system, these generators may not be able to maintain synchronous operation and may lose step-out. If some generators are left out of step, other generators will also lose step-out in a chain reaction, making it impossible to maintain the stability of the power system. This may result in a blackout, a large-scale blackout. Power system stabilization systems are known that perform control to ensure a stable supply of power even when an accident occurs in the power system. Power system stabilization systems prevent the remaining generators from losing step-out by limiting the power supply (hereafter referred to as power control) to cut off some generators in the power system from the system, thereby maintaining stable operation of the power system. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-099065 A [Patent Document 2] Patent Publication No. 2021-164359 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional power grid stabilization systems were often designed to withstand accident scenarios up to an N-2 accident, which is an accident involving the simultaneous loss of two pieces of equipment in a power grid, such as caused by the failure of two transmission lines.

[0005] However, in recent years, there has been a demand for strengthening the resilience of power systems so that they can continue to operate even when various natural disasters occur, and it is necessary to take measures against more severe accidents. For example, in a power system, there is a possibility that three or more pieces of equipment in the power system may be lost simultaneously, causing failures in three or more transmission lines. Power system stabilization systems are now required to respond to N-4 accidents, which are accidents involving the simultaneous loss of four pieces of equipment in the power system, caused by, for example, the failure of four transmission lines. However, with conventional power system stabilization systems, depending on the power control content of the calculated N-4 accident countermeasures, there was a risk that excessive power control would occur and the system would not be able to be stabilized.

[0006] The present embodiment is intended to solve the above-mentioned problem, and aims to provide a power system stabilization system, a computer program for the power system stabilization system, and a power system stabilization method that make it possible to avoid excessive power control during an N-4 accident. [Means for solving the problem]

[0007] The power system stabilization system of the embodiment is a power system stabilization system including a central processing unit that acquires system information from a power system at regular intervals and determines a target for electrical control for each assumed accident, and has the following configuration. (1) The central processing unit includes an N-2 accident countermeasure decision unit and an N-4 accident countermeasure decision unit. (2) The N-2 accident countermeasures decision unit includes an N-2 stability calculation unit that calculates the stability of the power system in each of a plurality of N-2 envisaged accidents and determines the power control target for each of the N-2 envisaged accidents, and an N-2 control table creation unit that creates an N-2 control table by associating the power control target for each of the N-2 envisaged accidents determined by the N-2 stability calculation unit with the N-2 envisaged accident. (3) The N-4 accident countermeasure decision unit includes an N-4 stability calculation unit that calculates the stability of the power system in an N-4 assumed accident and determines the power control targets for each N-4 assumed accident. (4) The N-4 stability calculation unit performs stability calculations using the contents of the N-2 control table created by the N-2 control table creation unit. [Brief description of the drawings]

[0008] [Figure 1] 1 is an overall diagram illustrating a configuration of a power system stabilization system according to a first embodiment. FIG. [Diagram 2] 4 is a flowchart showing an operation of the power system stabilization system according to the first embodiment. [Diagram 3] FIG. 11 is an overall diagram illustrating a configuration of a power system stabilization system according to a second embodiment. [Figure 4] FIG. 1 is a conceptual diagram illustrating the interval between two N-2 postulated accidents. [Diagram 5] FIG. 1 is a conceptual diagram illustrating the sequence of occurrence of two N-2 scenario accidents. [Figure 6] 10 is a flowchart showing an operation of the power system stabilization system according to the second embodiment. [Figure 7] FIG. 13 is an overall diagram illustrating a configuration of a power system stabilization system according to a third embodiment. [Figure 8] FIG. 13 is a conceptual diagram illustrating the calculation cycles of N-2 accident countermeasures and N-4 accident countermeasures. [Figure 9] 13 is a flowchart showing an operation of the power system stabilization system according to the third embodiment. [Figure 10] FIG. 13 is an overall diagram illustrating a configuration of a power system stabilization system according to a fourth embodiment. [Figure 11] 13 is a flowchart showing an operation of the power system stabilization system according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [1. First embodiment] [1-1. Overall composition] The first embodiment will be specifically described below with reference to the drawings. In the following description, when there are multiple devices or components with the same configuration, they will be described with the same reference numerals. Furthermore, multiple identical components will be distinguished by adding a suffix such as "1" or "2" to the end of a common reference numeral with a hyphen "-" between them. Note that when multiple identical components are not to be distinguished from one another, only the common reference numerals will be shown and the suffixes will be omitted.

[0010] 1 is a schematic diagram showing an example of the configuration of a power system stabilization system S according to a first embodiment. The power system stabilization system S includes, for example, a central processing unit 1, a central control unit 2, a fault detection terminal device 3, and a control terminal device 4. The power system stabilization system S is connected to a power system P and a power supply information network N.

[0011] As mentioned above, "power control" refers to power source restrictions that cut off some generators from the power grid P. Also, "power control amount" refers to the output power of the generators that are controlled. Note that "power control amount" is sometimes called "control amount."

[0012] The central processing unit 1, the central control device 2, the accident detection terminal device 3, and the control terminal device 4 are realized by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software).

[0013] Furthermore, some or all of these components may be realized by hardware (including circuitry) such as an LSI (Large Scale Integrated circuit), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Cate Array), or a GPU (Graphics Processing Unit), or may be realized by a combination of software and hardware.

[0014] (power system) The power system P is a power supply network including a series of power facilities that generate power and supply the generated power to load facilities of consumers. The power system P is composed of a plurality of power devices that generate and transmit power. The power devices are composed of power facilities (also called system facilities) such as generators, bus bars, transformers, transmission lines, phase modifying equipment, circuit breakers, and disconnecting switches. Note that detailed configuration of the power system P is not shown in the figures.

[0015] A generator is a facility that generates electricity using hydroelectric power, thermal power, nuclear power, or the like. The generator may be a renewable energy power source that generates electricity using renewable energy such as wind power or solar power. A plurality of generators are arranged in a power system P. It is the generators that are the targets of electrical control in order to stabilize unstable phenomena that occur when a postulated accident occurs in the power system P.

[0016] A circuit breaker is a device that interrupts the flow of electricity generated by a generator and transmitted through a transmission line, a transformer, and a busbar. When performing power control in the power system stabilization system S, the circuit breaker is controlled to disconnect the generator from the power system P. The circuit breaker is controlled by the central control device 2 via the control terminal device 4.

[0017] (Power supply information network) The power supply information network N is a communication network that enables communication between the power system P and the central processing unit 1. The power supply information network N performs communication by wire or wirelessly. The power supply information network N includes a communication circuit and a communication device, and may be configured by a dedicated communication line using, for example, microwave radio or optical fiber.

[0018] Communication is performed between the central processing unit 1 and measurement devices (not shown) arranged in the power system P via the power supply information network N. The measurement devices are configured to be able to measure the status of power equipment such as generators, circuit breakers, disconnecting switches, bus bars, transmission lines, and transformers. The measurement devices are installed in substations and power plants. System information measured by the measurement devices of each piece of power equipment in the power system P is transmitted to the central processing unit 1 via the power supply information network N.

[0019] (Accident detection terminal device) The accident detection terminal device 3 is a terminal device in which a contact information input circuit, a voltage / current input circuit, an active power measurement circuit, a transmission / reception circuit, etc. are configured with digital relays. The accident detection terminal device 3 is configured to be able to acquire system information and accident information in the power system P and transmit it to the central control device 2. A plurality of accident detection terminal devices 3 are installed at substations etc. that can detect assumed accidents.

[0020] The system information is information related to the connection state and power supply and demand state of the power system P detected by the fault detection terminal device 3. The system information includes, for example, on / off information of power devices in the power system P and measurement information related to the power supply and demand state. The on / off information is information related to the open / close state of circuit breakers, disconnectors, etc. The measurement information includes information related to the generator output, load, active power and reactive power of the transmission line, and bus voltage of each electric power station.

[0021] The fault detection terminal device 3 receives on / off information of breakers, disconnectors, etc. through a contact information input circuit. In addition, the active power measurement circuit uses the voltage and current information received through the voltage and current input circuit to measure the active power of the power source output, load, and transmission line, and creates system information.

[0022] The accident information is information about an accident that has occurred in a power device in the power system P. For example, when an accident occurs in a power transmission line, the accident information is information indicating the power device involved in the accident and the nature of the accident. The accident detection terminal device 3 inputs, for example, an operation signal of a fault clearance relay and on / off information of a circuit breaker through a contact information input circuit, and creates the accident information.

[0023] (Control terminal device) The control terminal device 4 is a terminal device in which a contact information input circuit, a contact information output circuit, a voltage / current input circuit, an active power measuring circuit, a transmitting / receiving circuit, etc. are configured using digital relays. The control terminal device 4 is configured to control a circuit breaker using the contact information output circuit based on a control command received from the central control device 2, and to be able to disconnect a generator designated as a target for electrical control from the power system P. A plurality of control terminal devices 4 are installed at power plants and the like that have power sources to be targeted for electrical control.

[0024] (Central Control Unit) The central control device 2 is a control device that periodically obtains system information from the accident detection terminal device 3, and uses the latest state of the power system P to select a generator to be controlled and output a control command. The central control device 2 is composed of a digital relay equipped with a transmitting / receiving circuit, etc. The central control device 2 is connected to the central processing unit 1, the accident detection terminal device 3, and the control terminal device 4. When an assumed accident actually occurs, the central control device 2 transmits a control command to the control terminal device 4 to shut off the generator, for the generator to be controlled in the control table previously obtained by the central processing unit 1. The central control device 2 is installed in a substation of a general electricity transmission and distribution company, etc.

[0025] (central processing unit) The central processing unit 1 is a processing unit that periodically receives system information of the power system P via the power supply information network N, and determines the power control target by calculation using the latest state of the power system P. The central processing unit 1 is installed in the central load dispatching center of a general electricity transmission and distribution company. The central processing unit 1 includes an information transmission unit 101, a system model creation unit 102, a state estimation unit 103, an N-2 accident countermeasure decision unit 110, an N-4 accident countermeasure decision unit 120, and a control table downstream transmission unit 130.

[0026] The central processing unit 1 may include a storage unit (not shown) for storing various types of information. The storage unit is a storage unit that stores various types of information necessary for the operation of the power system stabilization system S. The storage unit is configured with a storage medium such as a semiconductor memory or a hard disk. The storage unit stores anticipated accident conditions in the power system P, system information acquired via the power supply information network N, data and calculation results created by each component of the central processing unit 1, etc. The stored information is configured to be usable for the calculations of each component of the central processing unit 1 and for output to the central control device 2.

[0027] The information transmission unit 101 is a processing unit that is connected to the power supply information network N and acquires system information at regular intervals. In the example of FIG. 1, the information transmission unit 101 acquires system information via the power supply information network N, but the information transmission unit 101 may be configured to acquire the system information from the power system P via a communication network different from the power supply information network N. The information transmission unit 101 transmits the received system information to the system model creation unit 102.

[0028] The system model creation unit 102 is a processing unit that creates a system model based on the system information acquired by the information transmission unit 101 and various setting information stored in advance. The system model creation unit 102 creates a system model that represents the system state at that time point before the occurrence of an accident, based on the acquired system information and system equipment data stored in advance. The system model creation unit 102 transmits the created system model to the state estimation unit 103.

[0029] The system model is data that models the power system P. The system model may be composed of nodes and branches. The nodes are the digitization of buses, generators, and loads, and are information in which information such as electric machine output, active power and reactive power of the load, and bus voltage is associated with a node number, which is identification information. The branches are the digitization of transmission lines and transformers, and are information in which information such as node numbers of connection destinations (start node and end node), number of operating lines, and impedance is associated with a branch number, which is identification information.

[0030] The state estimation unit 103 is a calculation unit that estimates the system state. The state estimation unit 103 calculates the latest system state in the system model created by the system model creation unit 102 using the system information acquired by the information transmission unit 101. The state estimation unit 103 estimates the most likely system state using, for example, the weighted least squares method. The state estimation unit 103 transmits the calculated state estimation result to the N-2 accident countermeasure decision unit 110 and the N-4 accident countermeasure decision unit 120.

[0031] The N-2 accident countermeasure decision unit 110 is a processing unit that decides the target of power control in the event of an N-2 accident. The N-2 accident countermeasure decision unit 110 has an N-2 assumed accident selection unit 111, an N-2 stability calculation unit 112, and an N-2 control table creation unit 113.

[0032] The N-2 contingency selection unit 111 is a processing unit that uses the state estimation calculation result calculated by the state estimation unit 103 as input data and determines the N-2 contingency to be the target of stability calculation. The N-2 contingency selection unit 111 is configured to select two or more N-2 contingency from a plurality of N-2 contingency events set in advance. The N-2 contingency selection unit 111 transmits the determined N-2 contingency to the N-2 stability calculation unit 112.

[0033] Here, the N-2 contingency selection unit 111 is configured to be able to select contingencies for multiple routes of the power transmission network in the power system P. For example, the N-2 contingency selection unit 111 can select an N-2 contingency on route A and an N-2 contingency on route B.

[0034] The N-2 stability calculation unit 112 is a calculation unit that calculates the stability of the power system P in an N-2 contingency. The N-2 stability calculation unit 112 is configured to calculate the stability for each of the N-2 contingency of the multiple routes determined by the N-2 contingency selection unit 111. The N-2 stability calculation unit 112 calculates the stability for, for example, the N-2 contingency on route A and the N-2 contingency on route B.

[0035] Specifically, the N-2 stability calculation unit 112 performs stability calculation for the N-2 contingency received from the N-2 contingency selection unit 111, using the state estimation calculation result of the state estimation unit 103 as input data. The N-2 stability calculation unit 112 calculates one or more of transient stability, steady state stability, frequency stability, and voltage stability as stability. Based on the calculated stability, the N-2 stability calculation unit 112 evaluates whether the power system P can be operated stably.

[0036] If the result of the stability evaluation is stable, the N-2 stability calculation unit 112 ends the stability calculation. The N-2 stability calculation unit 112 determines the power control target selected in the calculation that is stable as the power control target for N-2 accident countermeasures, and transmits it to the N-2 control table creation unit 113. On the other hand, if the result of the stability evaluation is unstable, the N-2 stability calculation unit 112 is configured to select an additional power control target and perform the N-2 stability calculation again. The N-2 stability calculation unit 112 performs the N-2 stability calculation while changing the power control target until the result of the stability evaluation becomes stable.

[0037] The N-2 control table creation unit 113 sets, in the N-2 control table, the power control targets of the N-2 accident countermeasures calculated by the N-2 stability calculation unit 112. The N-2 control table creation unit 113 creates the N-2 control table by associating the identification information of the determined power control targets with the N-2 assumed accident conditions.

[0038] An example of the control table created by the N-2 control table creating unit 113 is shown in Table 1. [Table 1]

[0039] In the example of Table 1, generators G1 and G2 are associated as targets for power control in the event of a two-line fault on route A. Also, generators G1 and G3 are associated as targets for power control in the event of a two-line fault on route B. The N-2 control table creation unit 113 transmits the created N-2 control table to the N-4 fault countermeasure decision unit 120 and the control table downstream transmission unit 130.

[0040] The N-4 accident countermeasure decision unit 120 is a processing unit that decides the target of power control in the event of an N-4 accident. The N-4 accident countermeasure decision unit 120 has an N-4 assumed accident selection unit 121, an N-4 stability calculation unit 122, and an N-4 control table creation unit 123.

[0041] The N-4 contingency selection unit 121 is a processing unit that determines the N-4 contingency to be the target of the stability calculation. The N-4 contingency selection unit 121 receives the state estimation calculation result calculated by the state estimation unit 103 as input data, and determines the N-4 contingency based on the N-2 contingency selected by the N-2 contingency selection unit 111.

[0042] An N-4 accident occurs as a combination of N-2 accidents. Therefore, an N-4 contingent accident is, for example, a case in which one of two N-2 accidents occurs on route A and the other occurs on route B. In this way, the N-4 contingent accident selection unit 121 is configured to select one N-4 contingent accident from the combination of N-2 contingent accidents selected by the N-2 contingent accident selection unit 111 from a plurality of N-4 contingent accidents set in advance. The N-4 contingent accident selection unit 121 transmits the determined N-4 contingent accident to the N-4 stability calculation unit 122.

[0043] The N-4 stability calculation unit 122 is a calculation unit that calculates the stability of the power system P in an N-4 contingency. The N-4 stability calculation unit 122 performs stability calculation for the N-4 contingency received from the N-4 contingency selection unit 121. At this time, the N-4 stability calculation unit 122 uses the contents of the N-2 control table created by the N-2 control table creation unit 113 as the result of an N-2 contingency countermeasure in the calculation, in addition to the state estimation calculation result of the state estimation unit 103.

[0044] That is, the N-2 control table created by the N-2 control table creation unit 113 is referenced, and the power control targets of the N-2 accident countermeasures on route A and route B in the N-2 control table are set in advance as power control targets of the N-4 accident countermeasures. Then, stability calculation is performed for the N-4 assumed accident. As a result, the N-4 stability calculation unit 122 does not start the stability calculation from a state where power control is not performed, but starts the stability calculation from a state where the power control targets of the N-2 accident countermeasures are being powered down. For example, when the contents of the N-2 control table in Table 1 above are inherited, the N-4 stability calculation unit 122 starts the stability calculation from a state where the generators G1, G2, and G3 are being controlled.

[0045] The N-4 stability calculation unit 122 calculates one or more of the following stability: transient stability, steady state stability, frequency stability, and voltage stability. Based on the calculated stability, the N-4 stability calculation unit 122 evaluates whether the power system P can be stably operated.

[0046] If the result of the stability evaluation is stable, the N-4 stability calculation unit 122 ends the stability calculation. The N-4 stability calculation unit 122 determines the power control target selected in the calculation that is stable as the power control target for N-4 accident countermeasures, and transmits it to the N-4 control table creation unit 123. On the other hand, if the result of the stability evaluation is unstable, the N-4 stability calculation unit 122 is configured to select an additional power control target and perform the N4 stability calculation again. The N-4 stability calculation unit 122 performs the N-4 stability calculation while changing the power control target until the result of the stability evaluation becomes stable.

[0047] The N-4 control table creation unit 123 sets in the N-4 control table the power control targets of the N-4 accident countermeasures calculated by the N-4 stability calculation unit 122. The N-4 control table creation unit 123 creates the N-4 control table by associating the identification information of the determined power control targets with the N-4 assumed accident conditions.

[0048] An example of the N-4 control table created by the N-4 control table creation unit 123 is shown in Table 2. The control table in Table 2 is an N-4 control table obtained by carrying out a stability calculation following the N-2 control table in Table 1 above. [Table 2]

[0049] The example in Table 2 assumes a case where an N-4 accident occurs due to a combination of a double-line accident on route A and a double-line accident on route B. In this example, as shown in Table 1, it is assumed that generators G1 and G2 are powered down when a double-line accident on route A occurs, and generators G1 and G3 are powered down when a double-line accident on route B occurs. In the case of an N-4 accident (route A accident + route B accident), stability calculations are performed with the generators in the route A double-line accident and route B double-line accident powered down.

[0050] With reference to Table 2, it can be seen that the power system P became unstable as a result of carrying out a stability calculation using the contents of Table 1, so that additional power control was performed on G4 and the stability calculation was then performed, resulting in stability. That is, Table 2 shows an example in which stability is achieved by carrying out additional power control after implementing N-2 accident countermeasures for two routes, route A and route B. From the above, in Table 2, generators G1, G2, G3, and G4 are associated as targets for power control in the case of an N-4 assumed accident. The N-4 control table creation unit 123 transmits the created N-4 control table to the control table downstream transmission unit 130.

[0051] The control table downstream transmission unit 130 is a transmission unit that transmits the control table to the central control device 2. The control table downstream transmission unit 130 transmits, to the central control device 2, each of the N-2 control table created by the N-2 control table creation unit 113 and the N-4 control table created by the N-4 control table creation unit 123.

[0052] [1-2. Operation of the First Embodiment] The procedure for determining the control target of this embodiment will be described with reference to Fig. 2. Fig. 2 is a flowchart showing the process of determining the control target by the power system stabilization system S of this embodiment. Fig. 2 is a diagram showing the flow of a program when the central processing unit 1 is configured with software modules. The program is built into the central processing unit 1. In the following explanation, the flow for determining the control target will be specifically explained, and explanations regarding the actual accident content and the shutoff of the control target will be omitted.

[0053] The information transmission unit 101 of the central processing unit 1 receives system information from the power supply information network N at regular intervals (step S01) and transmits it to the system model creation unit 102. The system model creation unit 102 creates a system model based on the system information acquired by the information transmission unit 101 and various setting information stored in advance (step S02). The state estimation unit 103 uses the system information acquired by the information transmission unit 101 to calculate the latest system state in the system model created by the system model creation unit 102 (step S03).

[0054] The N-2 contingency selection unit 111 uses the state estimation calculation result calculated by the state estimation unit 103 as input data and determines the N-2 contingency to be the target of the stability calculation (step S04). For example, the N-2 contingency selection unit 111 selects the N-2 contingency on the A route and the N-2 contingency on the B route.

[0055] The N-2 stability calculation unit 112 calculates the stability of the N-2 contingency on the A route determined by the N-2 contingency selection unit 111 (step S05a). If the result of the stability evaluation is stable, the N-2 stability calculation unit 112 ends the stability calculation (step S06a, YES).

[0056] On the other hand, if the result of the stability evaluation is unstable (step S06a, NO), the N-2 stability calculation unit 112 selects an additional power control target (step S07a). After selecting the additional power control target, the N-2 stability calculation unit 112 returns to step S05a and performs the N-2 stability calculation again. The N-2 stability calculation unit 112 repeats steps S05a to S07a until the result of the stability calculation in step S06a becomes stable.

[0057] Similarly, the N-2 stability calculation unit 112 calculates the stability for the N-2 contingency on the B route determined by the N-2 contingency selection unit 111 (step S05b). If the result of the stability evaluation is stable, the N-2 stability calculation unit 112 ends the stability calculation (step S06b, YES).

[0058] On the other hand, if the result of the stability evaluation is unstable (step S06b, NO), the N-2 stability calculation unit 112 selects an additional power control target (step S07b). After selecting the additional power control target, the N-2 stability calculation unit 112 returns to step S05b and performs the N-2 stability calculation again. The N-2 stability calculation unit 112 repeats steps S05b to S07b until the result of the stability calculation in step S06b becomes stable.

[0059] The N-2 control table creation unit 113 sets the power control target of the N-2 accident countermeasure calculated by the N-2 stability calculation unit 112 in the N-2 control table (step S08). The N-2 control table is handed over to the N-4 stability calculation unit 122 and the control table downstream transmission unit 130.

[0060] The N-4 contingency selection unit 121 determines an N-4 contingency to be a target of stability calculation based on the N-2 contingency selected by the N-2 contingency selection unit 111 (step S09). The N-4 contingency selection unit 121 selects, for example, the simultaneous occurrence of accidents on route A and route B as an N-4 contingency.

[0061] The N-4 stability calculation unit 122 sets the N-2 control table created by the N-2 control table creation unit 113 as the N-2 accident countermeasure result (step S10). For example, when the N-2 control table of Table 1 above is input, the N-4 stability calculation unit 122 sets the generators G1, G2, and G3 that have already been determined as targets of electrical control as the N-2 accident countermeasure result.

[0062] Then, the N-4 contingency selection unit 121 calculates the stability for the determined N-4 contingency (step S11). If the result of the stability evaluation is stable, the N-4 stability calculation unit 122 ends the stability calculation (step S12, YES).

[0063] On the other hand, if the result of the stability evaluation is unstable (step S12, NO), the N-4 stability calculation unit 122 selects an additional power control target (step S13). For example, if the result of the stability calculation performed after power control of the generators G1, G2, and G3 that are power control targets for the N-2 accident countermeasures is unstable, the N-4 stability calculation unit 122 selects additional power control of the generator G4. After selecting the additional power control target, the N-4 stability calculation unit 122 returns to step S11 and performs the N-4 stability calculation again. In step S12, the N-4 stability calculation unit 122 repeats steps S11 to S13 until the result of the stability calculation becomes stable.

[0064] The N-4 control table creation unit 123 sets the power control target of the N-4 accident countermeasure calculated by the N-4 stability calculation unit 122 in the N-4 control table (step S14). The N-4 control table is handed over to the control table downstream transmission unit 130.

[0065] [1-3. Effects of the first embodiment] (1) In the power system stabilization system S of the present embodiment, the central processing unit 1 acquires system information from a power system P at a constant period and determines a power control target for each assumed accident. The central processing unit 1 includes an N-2 accident countermeasure decision unit 110 and an N-4 accident countermeasure decision unit 120. The N-2 accident countermeasure decision unit 110 calculates the stability of the power system P in each of a plurality of N-2 assumed accidents and determines a power control target for each N-2 assumed accident. The N-4 accident countermeasures decision unit 120 includes an N-4 stability calculation unit 122 that calculates the stability of the power system P in the N-4 envisaged accident and determines the power control target for each N-4 envisaged accident, and an N-2 control table creation unit 113 that creates an N-2 control table by associating the power control target for each N-2 envisaged accident determined by the stability calculation unit 112 with the N-2 envisaged accident. The N-4 accident countermeasures decision unit 120 includes an N-4 stability calculation unit 122 that calculates the stability of the power system P in the N-4 envisaged accident and determines the power control target for each N-4 envisaged accident, and the N-4 stability calculation unit 122 performs stability calculations by taking over the contents of the N-2 control table created by the N-2 control table creation unit 113.

[0066] Conventional power grid stabilization systems did not have the functionality to determine the power control targets for N-4 assumed contingencies. In addition, when determining the power control targets for N-4 assumed contingencies using existing power grid stabilization systems, the power control contents for N-2 accident countermeasures and N-4 accident countermeasures are calculated independently.

[0067] For example, in a conventional power system stabilization system, when the targets of power control for N-2 accident countermeasures and the targets of power control for N-4 accident countermeasures are calculated, the control contents shown in the following Tables 3 and 4 are determined. [Table 3] [Table 4]

[0068] The contents of Table 3, which shows the power control targets for the N-2 assumed accident, are the same as those of Table 1 above. That is, in the example of Table 3, generators G1 and G2 are associated as the power control targets for the two-line accident on route A. Also, generators G1 and G3 are associated as the power control targets for the two-line accident on route B.

[0069] In the example of Table 4 showing the targets of power control for an N-4 assumed contingency, a case is assumed in which an N-4 contingency occurs due to a combination of a two-line fault on route A and a two-line fault on route B, similar to the example of Table 2 above. However, in conventional power system stabilization systems, the targets of power control for an N-4 assumed contingency are calculated independently. Therefore, in Table 4, generators G4, G5, and G6 are associated as targets of power control for an N-4 assumed contingency.

[0070] In the conventional power grid stabilization system described above, when an N-4 fault occurs due to a combination of a double-circuit fault on route A and a double-circuit fault on route B, G1 and G2 are controlled in the double-circuit fault on route A, and G1 and G3 are controlled in the double-circuit fault on route B. Furthermore, G4, G5, and G6, which are not included in the targets for control in the N-2 fault, are controlled as targets for control in the N-4 fault. In other words, the conventional power grid stabilization system causes excessive power control in which generators G1, G2, G3, G4, G5, and G6 are controlled.

[0071] On the other hand, in the power system stabilization system S of this embodiment, the N-4 accident countermeasure decision unit 120 includes an N-4 stability calculation unit 122 that calculates the stability of the power system P in an N-4 assumed accident and determines the power control target for each N-4 assumed accident, and the N-4 stability calculation unit 122 performs stability calculation by taking over the contents of the N-2 control table created by the N-2 control table creation unit 113. In other words, the N-4 accident countermeasure decision unit 120 is configured to perform stability calculation by taking into account the power control contents in the N-2 assumed accident.

[0072] As explained above, the N-4 stability calculation unit 122 starts stability calculations after setting the N-2 control table created by the N-2 control table creation unit 113 as the N-2 accident countermeasure result, so the power control contents of the N-2 accident countermeasure and the N-4 accident countermeasure are not calculated independently. In such a power system stabilization system S, as shown in Table 2 above, generators G1, G2, G3, and G4 are determined as the power control targets for the N-4 assumed accident. In other words, by taking over the power control results of the N-2 accident countermeasure and determining the power control targets for the N-4 accident, it is possible to avoid excessive power control during an N-4 accident.

[0073] (2) The N-4 accident countermeasure decision unit 120 further includes an N-4 contingency selection unit 121 that determines an N-4 contingency from a combination of two N-2 contingency events.

[0074] In the power system stabilization system S of this embodiment, an N-4 contingency is considered as a combination of two N-2 contingencies. Therefore, it is possible to take over the power control results of the N-2 contingency countermeasures and determine the power control target for the N-4 contingency, making it possible to avoid excessive power control during an N-4 contingency.

[0075] (3) If the power system is unstable as a result of performing the stability calculation for the N-4 contingency accident from a state in which the power control objects for the two N-2 contingency accidents in the N-2 control table are controlled, the N-4 stability calculation unit 122 adds the power control objects to the power control objects for the two N-2 contingency accidents and performs the stability calculation again.

[0076] The N-4 stability calculation unit 122 determines the control target for the N-4 contingency by performing additional control on the control target for the N-2 contingency. This makes it possible to prevent excessive control during an N-4 contingency. In addition, since the calculation starts from a state in which the control target for the N-2 contingency has been controlled, the amount of calculation can be reduced compared to when the control target for the N-4 contingency is determined independently. In such a power system stabilization system S, it is possible to avoid prolonged calculation times and complication of the system.

[0077] [2. Second embodiment] [2-1. Overall composition] A power system stabilization system S according to the second embodiment will be described with reference to Figs. 3 and 4. The power system stabilization system S according to the present embodiment has basically the same configuration as the power system stabilization system S according to the first embodiment. However, in the power system stabilization system S according to the present embodiment, the N-4 assumed fault selection unit 121 further includes a fault interval setting unit 121a and a fault order setting unit 121b. Also, the N-4 stability calculation unit 122 further includes a control amount determination unit 122a.

[0078] The accident interval setting unit 121a is a processing unit that sets the interval between two N-2 contingent accidents in the N-4 contingent accident determined by the N-4 contingent accident selection unit 121. The interval between two N-2 contingent accidents will be described with reference to Fig. 4. As shown in Fig. 4, in the N-4 contingent accident, for example, the interval between the A route accident and the B route accident may vary from a typical interval of nmsec order to several tens to several hundreds of msec in some cases.

[0079] In order to assume such a case where the interval between two N-2 assumed accidents is different, the accident interval setting unit 121a sets the interval between two N-2 assumed accidents. The accident interval setting unit 121a may be configured to set the interval between two N-2 assumed accidents using a time interval that is set in advance. In addition, the interval between two N-2 assumed accidents can also be set using a value input by an operator via an input unit (not shown) or the like.

[0080] The accident order setting unit 121b is a processing unit that sets the occurrence order of two N-2 assumed accidents in the N-4 assumed accident determined by the N-4 assumed accident selection unit 121. In order to assume a case where the occurrence order of the two N-2 assumed accidents is different, the accident order setting unit 121b sets the occurrence order of the two N-2 assumed accidents. For example, as shown in FIG. 5, it may be a case where the A route accident occurs first, or a case where the B route accident occurs first.

[0081] As described above, the power system stabilization system S of this embodiment is configured such that the accident conditions are changed for one N-4 assumed accident by the accident interval setting unit 121a and the accident sequence setting unit 121b, and the N-4 stability calculation unit 122 performs stability calculation for N-4 assumed accidents under a plurality of accident conditions. The manner in which the accident conditions are changed includes a manner in which the accident interval is changed, a manner in which the accident sequence is changed, and a manner in which both the accident interval and the accident sequence are changed.

[0082] The control amount determination unit 122a is a processing unit that compares and determines the control amount for the results of stability calculations for multiple N-4 assumed accidents. The control amount refers to the amount of generators that are subject to power control. The control amount determination unit 122a compares the results of stability calculations for, for example, two accident conditions, determines the power control target for the accident condition with the greater control amount as the power control target for the N-4 accident countermeasure, and transmits the determined result to the N-4 control table creation unit 123.

[0083] [2-2. Operation of the Second Embodiment] The procedure for determining the power control target in this embodiment will be described with reference to Fig. 6. Fig. 6 is a flowchart showing the process for evaluating the effectiveness ranking of stabilization control candidates. In the following, the flow for determining the power control target in the N-4 accident countermeasure decision unit 120 will be specifically described. Up to step S08, the process is the same as in the above embodiment, so the description will be omitted.

[0084] The N-4 contingency selection unit 121 determines an N-4 contingency to be a target of stability calculation based on the N-2 contingency selected by the N-2 contingency selection unit 111 (step S09). In the example of Fig. 6, when determining an N-4 contingency, the accident order setting unit 121b sets two accident conditions for one N-4 contingency: a case where an A route accident occurs first and a case where a B route accident occurs first.

[0085] Therefore, in steps S10a to S13a, the N-4 stability calculation unit 122 performs stability calculation under accident conditions where an A route accident occurs first. Also, in steps S10b to S13b, the N-4 stability calculation unit 122 performs stability calculation under accident conditions where a B route accident occurs first. The specific calculation flow is the same as steps S10 to S13 in the above embodiment.

[0086] When the stability calculation using the accident condition under which the A route accident occurs first and the accident condition under which the B route accident occurs first is completed, the control amount determination unit 122a compares the control amounts that are the results of the stability calculation under the two accident conditions (step S15). The control amount determination unit 122a determines the power control target under the accident condition with a large control amount as the power control target for the N-4 accident countermeasure, and transmits it to the N-4 control table creation unit 123.

[0087] The N-4 control table creation unit 123 sets the power control target of the N-4 accident countermeasure, which is determined to have a large control amount by the control amount determination unit 122a, in the N-4 control table (step S16). The N-4 control table is handed over to the control table downstream transmission unit 130.

[0088] [2-3. Effects of the second embodiment] (1) The N-4 contingency selection unit 121 includes an accident interval setting unit 121a that sets the interval between two N-2 contingency accidents, and the N-4 stability calculation unit 122 includes a control amount determination unit 122a that compares and determines the control amounts of multiple stability calculation results, and the control amount determination unit 122a determines the power control target for the accident condition with the large control amount as the power control target for the N-4 accident countermeasure from the multiple stability calculation results calculated using multiple accident conditions in which the interval between two N-2 contingency accidents is changed.

[0089] In an N-4 accident, two N-2 accidents do not necessarily occur simultaneously. The accident interval setting unit 121a makes it possible to perform stability calculations taking into account changes in the occurrence interval of two N-2 accidents. When the severity of stability differs due to changes in the accident interval, the control amount of the power control target required for stabilization may change. Therefore, by performing stability calculations under a plurality of accident conditions, it is possible to identify accident conditions that require more control. Furthermore, by using the control amount determination unit 122a to determine the power control target of an accident condition with a large control amount as the power control target for N-4 accident countermeasures, it is possible to prevent excessive power control while suppressing underpower control that occurs when the simultaneous occurrence of an A route accident and a B route accident is assumed. Therefore, it is possible to determine a more appropriate power control target for N-4 accident countermeasures.

[0090] (2) The N-4 contingency selection unit 121 includes an accident order setting unit 121b that sets the order of occurrence of two N-2 contingency accidents, and the N-4 stability calculation unit 122 includes a control amount determination unit 122a that compares and determines the control amounts of multiple stability calculation results, and the control amount determination unit 122a determines the power control target for the accident condition with the largest control amount as the power control target for the N-4 accident countermeasure from the multiple stability calculation results calculated using multiple accident conditions that change the order of occurrence of the two N-2 contingency accidents.

[0091] As with the fault interval, the fault order setting unit 121b makes it possible to perform stability calculations taking into consideration changes in the occurrence order of two N-2 faults. If the severity of stability differs due to changes in the occurrence order, the control amount of the power control target required for stabilization may change. Therefore, by performing stability calculations under multiple fault conditions, it is possible to identify fault conditions that require more control. Furthermore, by using the control amount determination unit 122a to determine the power control target of the fault condition with a large control amount as the power control target for the N-4 fault countermeasure, it is possible to prevent excessive power control while suppressing underpower control that occurs when the simultaneous occurrence of a route A fault and a route B fault is assumed. Therefore, it is possible to determine a more appropriate power control target for the N-4 fault countermeasure.

[0092] [3. Modifications] In the power system stabilization system S of the modification of the first embodiment, the N-4 contingency selection unit 121 selects a case in which the accident aspect is severe from the N-2 contingency selected by the N-2 contingency selection unit 111, and determines the N-4 contingency. The severe accident aspect means an accident aspect with a large amount of control determined by the N-2 contingency countermeasure determination unit 110.

[0093] For example, an N-2 accident may progress to a severe accident due to failure of high-speed reclosing. In this embodiment, in selecting an N-4 assumed accident, for example, a case in which the accident state is severe due to failure of high-speed reclosing on route A and route B of the N-2 assumed accident is selected and selected as the N-4 assumed accident. Then, when the N-4 stability calculation unit 122 performs stability calculation of the N-4 assumed accident, it selects an accident case with the accident state with the largest control amount (such as H-Rec failure) from the N-2 control tables of each of route A and route B, and performs calculation from the state in which the electrical control target is controlled.

[0094] In this way, by inheriting the accident scenario that requires the greatest amount of control for each N-2 assumed accident from the N-2 control table and performing calculations for N-4 accident countermeasures, it is possible to target severe accident cases and prevent insufficient power supply.

[0095] [4. Third embodiment] A power system stabilization system S according to the third embodiment will be described with reference to Figs. 7 and 8. The power system stabilization system S according to this embodiment has basically the same configuration as the power system stabilization system S according to the first embodiment. However, in the power system stabilization system S according to this embodiment, the N-2 accident countermeasure decision unit 110 and the N-4 accident countermeasure decision unit 120 are configured to calculate accident countermeasures in parallel. That is, as shown in Fig. 7, the storage unit of the central processing unit 1 has an N-2 power control content database D1. The N-2 power control content database D1 stores an N-2 control table.

[0096] As shown in Fig. 8, the N-2 accident countermeasure decision unit 110 uses the system information for the current cycle to determine the target of power control for the N-2 accident. The N-4 accident countermeasure decision unit 120 is configured to perform calculations simultaneously with the N-2 accident countermeasure decision unit 110 by taking over the contents of N-2 accident countermeasures for all cycles and determining the target of power control for the N-4 accident.

[0097] 9, similarly to the above embodiment, the N-2 accident countermeasure decision unit 110 is configured to calculate the power control target of the N-2 accident countermeasure using the system information of the current cycle acquired by the information transmission unit 101 (steps S04 to S08). Then, in step S20, the N-2 control table created by the N-2 control table creation unit 113 is configured to be stored in the N-2 power control content database D1 of the storage unit.

[0098] In step S021, the N-4 accident countermeasure decision unit 120 retrieves the N-2 control table of the previous cycle from the N-2 power control content database D1. As in the above embodiment, the N-4 stability calculation unit 122 sets the power control target of the N-2 accident countermeasure in the retrieved N-2 control table of the previous cycle as the power control target of the N-4 accident countermeasure in advance, in addition to the state estimation calculation result of the state estimation unit 103. Then, the stability calculation is performed for the N-4 assumed accident, and the N-4 control table is created (steps S09 to S14).

[0099] As described above, the power system stabilization system of this embodiment further includes an N-2 power control content database D1 that stores the N-2 control table created by the N-2 control table creation unit 113, and the N-4 accident countermeasure decision unit 120 is configured to import the N-2 control table of the previous cycle from the N-2 power control content database D1 and perform stability calculations.

[0100] In the N-4 accident countermeasure, by inheriting the power control contents of the N-2 accident countermeasure from the previous cycle, it is possible to calculate the N-2 accident countermeasure and the N-4 accident countermeasure in parallel. This makes it possible to shorten the calculation cycle compared to when inheriting the power control contents of the N-2 accident countermeasure for the current cycle and calculating the N-4 accident countermeasure. In addition, although the results of the previous cycle are inherited, stabilization measures are performed using the system information of the current cycle, so insufficient control can be prevented.

[0101] [5. Fourth embodiment] A power system stabilization system S according to the fourth embodiment will be described with reference to Fig. 10. The power system stabilization system S of this embodiment has basically the same configuration as the power system stabilization system S according to the third embodiment. However, the power system stabilization system S of this embodiment further includes a flow for selecting an N-2 control table to be adopted during N-4 accident countermeasures. The power system stabilization system S of this embodiment further includes a power control content determination unit 140 as shown in Fig. 10.

[0102] The power control content determination unit 140 is a processing unit that compares the control amount of the N-2 control table of the current cycle with the N-2 control table of the previous cycle, and determines the N-2 control table with the larger control amount as the power control content. Note that although the power control content determination unit 140 is shown as an independent component in Fig. 10, it can also be regarded as the N-2 accident countermeasure determination unit 110 or as the N-4 accident countermeasure determination unit.

[0103] As shown in the flowchart of Fig. 11, the power control content determination unit 140 retrieves the N-2 control table of the current cycle and the N-2 control table of the previous cycle stored in the N-2 power control content database D1 (step S30). Then, in step S31, the control amount of the N-2 control table of the current cycle is compared with that of the N-2 control table of the previous cycle. If the power control content determination unit 140 determines that the control amount of the N-2 control table of the current cycle is greater (step S31 YES), the process proceeds to step S20 as in the third embodiment, and the N-4 accident countermeasure determination unit 120 retrieves the N-2 control table of the previous cycle from the N-2 power control content database D1 and performs stability calculation.

[0104] On the other hand, when the power control content determination unit 140 determines that the N-2 control table of the previous cycle has a larger control amount (step S31 NO), it proceeds to step S32, imports the N-2 control table of the current cycle, and performs the stability calculation from step S09 onwards again. That is, in the fourth embodiment, while performing the stability calculation based on the N-2 control table of the previous cycle as in the third embodiment, when the N-2 control table of the current cycle is created, the control amount is compared with that of the N-2 control table of the previous cycle. Then, when the N-2 control table of the previous cycle has a larger control amount, the stability calculation based on the N-2 control table of the current cycle is performed again.

[0105] As described above, the power system stabilization system of this embodiment further includes a power control content determination unit 140 that determines the power control content based on the control amount of the N-2 control table of the previous cycle and the N-2 control table of the current cycle, and when the power control content determination unit 140 determines that the N-2 control table of the previous cycle has a larger control amount, the N-4 accident countermeasures determination unit 120 is configured to import the N-2 control table of the current cycle and perform stability calculation again.

[0106] When calculating the stability of an N-4 accident using the N-2 control table of the previous cycle, if the control amount of the N-2 control table of the previous cycle is greater than that of the N-2 control table of the current cycle, there is a risk that the calculated power control target of the N-4 accident will be excessive. In this embodiment, only when the control amount of the N-2 accident countermeasure in the previous cycle is greater than that in the current cycle, the power control target of the N-4 accident is recalculated using the control contents of the N-2 control table of the current cycle. Therefore, it is possible to prevent excessive power control of the N-4 accident countermeasure while shortening the calculation cycle.

[0107] 6. Other embodiments In this specification, several embodiments of the present invention have been described, but these embodiments are presented as examples and are not intended to limit the scope of the invention. The above-mentioned embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope of the invention and its equivalents described in the claims, as well as in the scope and gist of the invention. [Explanation of symbols]

[0108] S: Power system stabilization system N: Power supply information network P: Power system 1: Central processing unit 2: Central control unit 3: Accident detection terminal device 4: Control terminal device 101: Information Transmission Department 102: System model creation department 103: State estimation unit 110: N-2 Accident Countermeasures Decision-making Department 111: N-2 Contingency Selection Section 112:N-2 stability calculation section 113: N-2 control table creation unit 120: N-4 Accident Countermeasures Decision-making Department 121: N-4 Contingency Selection Section 121a: Accident interval setting unit 121b: Accident sequence setting section 122:N-4 stability calculation section 122a: Control amount determination unit 123: N-4 control table creation section 130: Control table downstream transmission unit 140:Electronic content determination department D1:N-2 Electric Control Contents Database

Claims

1. A power system stabilization system having a central processing unit that acquires system information from a power system at a constant cycle and determines the target of power control for each assumed accident, The central processing unit includes an N-2 accident countermeasure decision unit and an N-4 accident countermeasure decision unit, The N-2 accident countermeasure decision-making unit: An N-2 stability calculation unit that calculates the stability of the power system in each of a plurality of N-2 assumed accidents and determines the power control target for each of the N-2 assumed accidents; An N-2 control table creation unit that creates an N-2 control table by associating the power control target for each N-2 assumed accident determined by the N-2 stability calculation unit with the N-2 assumed accident, The N-4 accident countermeasure decision-making unit: An N-4 stability calculation unit that calculates the stability of the power system in an N-4 assumed accident and determines the power control target for each N-4 assumed accident, The N-4 stability calculation unit performs stability calculations by taking over the contents of the N-2 control table created by the N-2 control table creation unit. Power system stabilization system.

2. The power system stabilization system according to claim 1, wherein the N-4 contingency countermeasure decision unit further includes an N-4 contingency selection unit that determines the N-4 contingency from a combination of two of the N-2 contingency.

3. 3. The power system stabilization system according to claim 1 or 2, wherein, when the power system is unstable as a result of performing a stability calculation for the N-4 contingency from a state in which the power control objects for the two N-2 contingency events in the N-2 control table are controlled, the N-4 stability calculation unit adds the power control objects to the power control objects for the two N-2 contingency events and performs a stability calculation again.

4. The N-4 contingency selection unit includes an accident interval setting unit that sets an interval between two of the N-2 contingency accidents, The N-4 stability calculation unit includes a control amount determination unit that compares and determines control amounts of a plurality of stability calculation results, The control amount determination unit determines the power control target of the accident condition with a large control amount as the power control target of the N-4 accident countermeasure from the plurality of stability calculation results calculated using a plurality of accident conditions in which the interval between the two N-2 assumed accidents is changed, The power system stabilization system according to claim 2.

5. The N-4 contingency selection unit includes an accident order setting unit that sets an occurrence order of the two N-2 contingency accidents, The N-4 stability calculation unit includes a control amount determination unit that compares and determines control amounts of a plurality of stability calculation results, The control amount determination unit determines the power control target of the accident condition with a large control amount as the power control target of the N-4 accident countermeasure from the plurality of stability calculation results calculated using a plurality of accident conditions in which the occurrence order of the two N-2 assumed accidents is changed, The power system stabilization system according to claim 2.

6. The N-4 stability calculation unit is configured to take over the accident state having the largest control amount in each of the two N-2 assumed accidents from the N-2 control table and perform stability calculation. The power system stabilization system according to claim 2.

7. Further includes an N-2 power control content database that stores the N-2 control table created by the N-2 control table creation unit, The power system stabilization system according to claim 1, wherein the N-4 accident countermeasure decision unit is configured to retrieve the N-2 control table of the previous cycle from the N-2 power control content database and perform the stability calculation.

8. Further provided is an electrical control content determination unit that determines electrical control content based on the control amount of the N-2 control table of the previous cycle and the N-2 control table of the current cycle, 8. The power system stabilization system according to claim 7, wherein when the power control content determination unit determines that the N-2 control table of the previous cycle has a larger control amount, the N-4 accident countermeasure determination unit is configured to import the N-2 control table of the current cycle and perform the stability calculation again.

9. A computer program for a power system stabilization system having a central processing unit that acquires system information from a power system at a constant period and determines a target for power control for each assumed accident, A central processing unit of the power system stabilization system Execute an N-2 accident countermeasure decision step and an N-4 accident countermeasure decision step; The N-2 accident countermeasure decision step includes: An N-2 stability calculation step of calculating the stability of the power system in each of a plurality of N-2 assumed accidents and determining the power control target for each of the N-2 assumed accidents; An N-2 control table creation step of creating an N-2 control table by associating the power control target for each N-2 assumed accident determined by the N-2 stability calculation step with the N-2 assumed accident, The N-4 accident countermeasure decision step includes: An N-4 stability calculation step of calculating the stability of the power system in an N-4 assumed accident and determining the power control target for each N-4 assumed accident; The N-4 stability calculation step performs a stability calculation by taking over the contents of the N-2 control table created by the N-2 control table creation unit. A computer program for power system stabilization systems.

10. A power system stabilization method using a power system stabilization system having a central processing unit that acquires system information from a power system at a constant period and determines a power control target for each assumed accident, A central processing unit of the power system stabilization system, Execute an N-2 accident countermeasure decision step and an N-4 accident countermeasure decision step; The N-2 accident countermeasure decision step includes: An N-2 stability calculation step of calculating the stability of the power system in each of a plurality of N-2 assumed accidents and determining the power control target for each of the N-2 assumed accidents; An N-2 control table creation step of creating an N-2 control table by associating the power control target for each N-2 assumed accident determined by the N-2 stability calculation step with the N-2 assumed accident, The N-4 accident countermeasure decision step includes: An N-4 stability calculation step of calculating the stability of the power system in an N-4 assumed accident and determining the power control target for each N-4 assumed accident; The N-4 stability calculation step performs a stability calculation by taking over the contents of the N-2 control table created by the N-2 control table creation unit. Power system stabilization method.

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