System stabilization system

Abstract

To prevent step-out in advance, by correcting a power control amount necessary for preventing step-out at occurrence of an accident in a system.SOLUTION: A stability evaluation model generation unit of a system stabilization system prepares, before occurrence of an accident, model definition information for estimating a future value of phase angle deviation that is used for discrimination of presence or absence of the step-out of one or more power generators included in an electric power system, and a discrimination reference value that is used for discrimination of the presence or absence of the step-out of the power generators. A correction coefficient generation unit of the system stabilization system prepares, before the occurrence of an accident, correction preparation information for determining a correction value necessary for estimation of the future value of the phase angle deviation that is used for discrimination of the presence or absence of the step-out of the power generators. An additional power control execution unit of the system stabilization system adjusts the discrimination reference value on the basis of a measured value of the electric power system after the occurrence of an accident, and when discriminating that the power generators step out on the basis of the measured value of the electric power system before and after the occurrence of the accident, model definition information, the future value of the phase angle deviation predicted from the correction preparation information, and the discrimination reference value after the adjustment, selects an additional power control power generator and controls the power of the power generator.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In a system stabilization system aimed at stabilizing a power system, in preparation for an accident occurring in the system, a method is used in which transient stability calculations are periodically performed based on the power state before the accident occurs, and a generator (hereinafter also referred to as a power control unit) to be disconnected (hereinafter also referred to as cut-off or power control) is selected depending on the accident (for example, non-patent document 1).

[0003] In the above-mentioned power grid stabilization system, the power control machines necessary to prevent loss of synchronism in the event of a power grid accident are selected using transient stability calculations of a power grid model that reflects information about the power grid at intervals of one minute, etc. Therefore, if the state of the power grid changes during the transient stability calculation period due to a sudden change in the output of a renewable energy power source, there is a possibility that there will not be enough power control machines necessary to prevent loss of synchronism, and loss of synchronism cannot be prevented.

[0004] Also, some grid stabilization systems aimed at stabilizing the power grid implement a second shearing control using measured values ​​after a grid accident occurs in preparation for changes in shearing control required for grid stabilization caused by changes in the state of the power grid during a certain period for selecting shearing control machines required for grid stabilization (see, for example, Patent Document 1 and Patent Document 2).

[0005] The grid stabilization system implementing the above-mentioned second shearing control determines whether the generator will step out after the first shearing control, i.e., whether the power grid is stable or unstable, and if it is unstable, performs a stability determination for the case where the second shearing control is added, and selects the necessary second shearing control. In this case, the grid stabilization system implementing the second shearing control determines stability using the estimated phase angle deviation equivalent to one generator, but since it is assumed that the generator active power deviation used to calculate the phase angle deviation can be approximated by a sine function, if the true active power deviation deviates from the value of the approximated sine function, an error may occur in the stability determination result. In addition, in the grid stabilization system implementing the second shearing control, the state quantity used to calculate the phase angle deviation is also substituted with the active power deviation, so an error may occur in the stability determination result. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7034978 [Patent Document 2] Patent Publication No. 2022-038125 [Non-patent literature]

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

[0008] The problem that the present invention aims to solve is to provide a power system stabilization system that can improve the accuracy of stability determination when selecting the amount of power control required to stabilize the power system, and can prevent loss of synchronization in advance by correcting the amount of power control required to prevent loss of synchronization in the event of a system accident, even if the state of the power system changes due to a sudden change in the output of a renewable energy power source. [Means for solving the problem]

[0009] In the embodiment, the system stabilization system collects system information including at least active and reactive powers of the transmission lines constituting the power system to construct a system model, and performs a transient stability calculation for an assumed accident condition in advance to select a first shearing control generator for preventing a generator from losing synchronism for each assumed accident condition, and prevents the generator from losing synchronism by disconnecting the first shearing control generator selected in advance when a system accident occurs. The system stabilization system has a stability evaluation model generation unit, a correction coefficient generation unit, and an additional shearing control execution unit. The stability evaluation model generation unit prepares model definition information for estimating a future value of a phase angle deviation used to determine whether or not one or more generators included in the power system have lost synchronism and a discrimination reference value used to determine whether or not the one or more generators have lost synchronism, based on the result of the immediately preceding transient stability calculation. The correction coefficient generation unit prepares correction preparation information for obtaining a correction value required to estimate a future value of a phase angle deviation used to determine whether or not one or more generators included in the power system have lost synchronism, before the accident occurs. After an accident occurs, the additional power control execution unit adjusts the discrimination reference value prepared by the stability evaluation model generation unit based on the measurement values ​​of the power system before and after the accident occurs, the model definition information, the future value of the phase angle deviation predicted from the correction preparation information, and the adjusted discrimination reference value, and if it is determined that a generator included in the power system will go out of step, an additional power control generator is selected and controlled. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing an example of a configuration of a power supply system to which a grid stabilization system according to an embodiment is applied; [Diagram 2] 13 is a diagram showing an example of a calculation result used in a process performed by a stability limit correction ratio calculation unit. FIG. [Diagram 3] 6 is a diagram for explaining an example of a process performed by an active power deviation correction value function calculation unit. FIG. [Figure 4] FIG. 4 is a diagram illustrating an example of a difference between active power and electric torque. [Diagram 5]11 is a flowchart showing an example of a flow of processing performed by an additional power control executing unit. [Figure 6] FIG. 4 is a diagram illustrating an example of processing performed by an additional power control executing unit. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a power system stabilization system according to an embodiment will be described with reference to the drawings. In the following description, multiple components of the same type are distinguished by adding a numerical value such as "1" or "2" to the end of the reference numeral with a "-" (hyphen) between them. When multiple configurations of the same type are not to be distinguished from one another, adding a numerical value such as "1" or "2" to the end of the reference numeral with a "-" (hyphen) between them is omitted.

[0012] [Power supply system configuration] 1 is a block diagram showing an example of a configuration of a power supply system to which a power grid stabilization system according to an embodiment is applied. The power supply system includes, for example, a power grid 1, a transmission system 10, and a power grid stabilization system 20.

[0013] The power system 1 includes bus bars 2 (bus bars 2-1 to 2-5), power transmission lines 3 (power transmission lines 3-1 to 3-5), transformers 4 (transformers 4-1 to 4-4), generators 5 (generators 5-1 to 5-4), circuit breakers 6 (circuit breakers 6-1 to 6-4), information terminals 11 (information terminals 11-1 to 11-5), and control terminals 12 (control terminals 12-1, 12-2).

[0014] The transformer 4 transforms the voltage of the power generated by the generator 5 to a predetermined voltage. For example, the transformer 4-1 transforms the voltage of the power generated by the generator 5-1 to a predetermined voltage. The generator 5 indicates a power source using renewable energy such as solar power or wind power, which is connected to the power system by a DC / AC power converter, or a thermal power machine, nuclear power machine, hydroelectric power machine, or other device that generates power using a synchronous generator and supplies it to the power system. The circuit breaker 6 cuts off the supply of the power generated by the generator 5 to consumers. For example, the circuit breaker 6-1 cuts off the supply of the power generated by the generator 5-1. The transmission system 10 is composed of a communication network such as a dedicated communication line or the Internet, and transmits various information such as system information described later between the information terminal 11 and the power system stabilization system 20.

[0015] The information terminal 11 measures information about the power supplied from the generator 5 through the bus 2 to the consumer (hereinafter referred to as system information).

[0016] The system information includes power information on the supply and demand state of power in each component of the power system 1 (bus 2, transmission line 3, transformer 4, generator 5, circuit breaker 6, information terminal 11, and control terminal 12), and connection information on the connection state. The electric information included in the system information is the active power and reactive power of the transmission line 3 and the transformer 4, and the bus voltage applied to the bus 2. The connection information included in the system information is the connection state of the transmission line 3 and the transformer 4. The system information includes, for example, the voltage and phase angle of each bus 2 in the power system 1, the active power flow and reactive power flow of the transmission line 3, and start / stop information of the generator 5. For example, the information terminal 11-1 measures the system information including the power information on the power supplied by the transmission lines 3-1, 3-2, and 3-5 connected to the bus 2-1, and the connection information of the transmission line 3-1, etc.

[0017] The control terminal 12 controls the circuit breaker 6 in response to a control signal from the grid stabilization system 20, and controls the cutoff of the power supply from the generator 5. For example, the control terminal 12-1 controls the circuit breakers 6-1 and 6-2 in response to a control signal from the grid stabilization system 20, and controls the cutoff of the power supply via the bus 2-4.

[0018] In the power system 1, the range to the left of the transmission line 3-5 where system information is not available is referred to as the external system, and the range to the right of the transmission line 3-5 where system information is available is referred to as the internal system. In addition, an interconnection point described below refers to the bus 2-1, which is the boundary between the range where system information is available and the range where it is not available, and an interconnection line refers to the transmission line 3-5. The external system also includes multiple buses 2, transmission lines 3, transformers 4, generators 5, etc.

[0019] The power system stabilization system 20 acquires system information via the transmission system 10, performs transient stability calculations based on the acquired system information, and selects a shearing control machine that performs shearing control to maintain the stability of the power system 1 when a postulated accident occurs. Here, the shearing control machine is a generator 5 that cuts off the supply of power. In the following description, "accident" refers to a system accident.

[0020] In this embodiment, in addition to the transient stability calculation described above, the power grid stabilization system 20 determines whether or not additional power control is necessary based on measurement information after the occurrence of an accident, and if additional power control is necessary, selects a power control machine to perform additional power control.

[0021] The power grid stabilization system 20 includes a power control execution unit 30, a stability evaluation model generation unit 40, a correction coefficient generation unit 80, and an additional power control execution unit 50.

[0022] The power grid stabilization system 20 and the components included in the power grid stabilization system 20 realize the following functions by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of the functions of the power grid stabilization system 20 and the components included in the power grid stabilization system 20 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. Some or all of the functions of the power grid stabilization system 20 and the components included in the power grid stabilization system 20 may be realized by a dedicated LSI. The program may be stored in advance in a storage device (storage device with a non-transient storage medium) such as an HDD (Hard Disk Drive) or flash memory equipped in the power grid stabilization system 20 or the power supply system, or may be stored in a removable storage medium (non-transient storage medium) such as a DVD or CD-ROM, and installed in a storage device equipped in the power grid stabilization system 20 by attaching the storage medium to a drive device equipped in the power grid stabilization system 20 or the power supply system.

[0023] FIG. 1 shows a case where the power control execution unit 30, the stability evaluation model generation unit 40, the correction coefficient generation unit 80, and the additional power control execution unit 50 included in the power grid stabilization system 20 are each configured within the power grid stabilization system 20. In other words, the power control execution unit 30, the stability evaluation model generation unit 40, the correction coefficient generation unit 80, and the additional power control execution unit 50 are each illustrated as being integrated. However, these components are not limited to being integrated as illustrated in FIG. 1. For example, one or more of these components may be configured in a device different from the power grid stabilization system 20. In other words, the power grid stabilization system 20 may be configured by a plurality of separate devices.

[0024] The power control execution unit 30 is a functional unit that performs processing related to power control by conventional transient stability calculation. The stability evaluation model generation unit 40, the correction coefficient generation unit 80, and the additional power control execution unit 50 are functional units that perform processing related to additional power control.

[0025] The power control execution unit 30 includes a system information collection unit 31, a basic system memory unit 32, a system model creation unit 33, a stability calculation unit 34, a power control machine selection unit 35, a first-stage power control unit 36, and a calculation result memory unit 37.

[0026] The system information collector 31 acquires system information at preset intervals (for example, every minute) from the information terminal 11 via the transmission system 10. The system information collector 31 outputs the acquired system information to the system model creator 33.

[0027] The system model creation unit 33 creates a simulation model (hereinafter referred to as a system model) that represents the power flow state of the power system 1, based on the system information acquired by the information terminal 11 and the configuration information stored in the basic system storage unit 32. The basic system storage unit 32 stores the configuration information.

[0028] The configuration information is information about the configuration of each component of the power system 1. The configuration information is, for example, information indicating the impedance and inductance of the transmission lines 3 of the power system 1, interconnection information between the bus bars 2 and the transmission lines 3, and the size, number, and arrangement of each component of the power system 1.

[0029] The stability calculation unit 34 performs a system analysis simulation by transient stability calculation using a system model. The stability calculation unit 34 executes transient stability calculations in the case of occurrence of various assumed accidents set in advance, and judges whether the generator will not step out or will step out, that is, whether the power system is stable or unstable. The stability calculation unit 34 outputs the judgment result to the shearing control unit selection unit 35. When the judgment result by the stability calculation unit 34 is unstable, the shearing control unit selection unit 35 selects one of the generators that will step out as a shearing control unit and adds it. The stability calculation unit 34 executes a transient stability calculation under the condition of shutting off the shearing control unit selected by the shearing control unit selection unit 35, judges again whether it is stable or unstable, and outputs the judgment result to the shearing control unit selection unit 35. By repeating the exchange between the stability calculation unit 34 and the shearing control unit selection unit 35 until the judgment result becomes stable, the shearing control unit that can maintain the stability of the power system in the assumed accident is determined (selected). In addition, the series of processes performed immediately before the occurrence of a ground fault or the like to determine the first electrically controlled generator is referred to as the most recent calculation.

[0030] The shear control unit selection unit 35 outputs information on the shear control unit selected to stabilize the power system 1 when an assumed accident occurs to the first stage shear control unit 36. In addition, the stability calculation unit 34 stores various conditions and calculation results, including the system model used in the transient stability calculation and the shear control unit selection result, in the calculation result storage unit 37.

[0031] The first stage electrical control unit 36 ​​detects the occurrence of an accident and the accident conditions in the power system 1 via the transmission system 10, and sends a shutoff command to the control terminal 12 of a preselected electrical control machine in the event of an assumed accident corresponding to the accident conditions. This causes the corresponding generator 5 to be disconnected from the power system 1. The calculation result storage unit 37 stores various conditions and calculation results, including the system model used in the transient stability calculation and the selection result of the electrical control machine.

[0032] The stability evaluation model generation unit 40 includes an unstable side system model formulation unit 41, a stable side system model formulation unit 42, a discrimination criterion formulation unit 43, and an output change model formulation unit 44. The stability evaluation model generation unit 40 performs processing at the same cycle as the selection of the first power control, regardless of the occurrence of a fault.

[0033] The unstable side system model formulation unit 41 calculates various constants for calculating state quantities of the unstable generator group model under the accident conditions of each postulated accident. The unstable generator group model is a model that combines multiple generators 5 (unstable generator group) belonging to the unstable side system into one generator equivalent to the multiple generators. A generator 5 belonging to the unstable side system is a generator 5 that does not maintain stability in the event of a postulated accident, that is, a generator 5 that may become unstable, and is a generator 5 that is subject to electrical control in the event of the postulated accident.

[0034] The unstable side system model formulation unit 41, for example, examines (calculates) the internal voltage phase angle difference of each generator 5 based on the phase angle center of gravity of all generators 5, and determines that a generator whose calculated phase angle difference exceeds a predetermined specified value is a generator 5 belonging to the unstable side system.

[0035] Moreover, the unstable side system model formulation unit 41 calculates an inertia constant M1 of the unstable generator group model as various constants for calculating the state quantities of the unstable generator group model, as shown in (Equation 1).

[0036]

number

[0037] In formula 1, M i indicates the inertia constant of the generator 5 with identification number i belonging to the unstable side system. The identification number i (i = 0 to n) is a number that uniquely identifies an unstable generator (the generator 5 belonging to the unstable side system). n is an arbitrary natural number.

[0038] The stable side system model formulation unit 42 constructs in advance a function for estimating the total active power of the generators included in the external system under each fault condition, using the calculation results stored in the calculation result storage unit 37. In addition, the stable side system model formulation unit 42 calculates various constants for calculating the state quantities of the stable generator group model under the fault conditions of each assumed fault.

[0039] The stable generator group model is a model in which multiple generators 5 (stable generator group) belonging to the stable side system are combined into one generator equivalent to the multiple generators 5. The stable side system is a system that is estimated to maintain stability against a hypothetical accident, and is, for example, a collection of generators etc. located at a distance from the location where the hypothetical accident occurs in terms of electrical connection. This is because a generator 5 installed at a location away from the location where the hypothetical accident is expected to occur is less susceptible to the effects of the hypothetical accident and is considered to maintain stability against the hypothetical accident.

[0040] The stable side system model formulation unit 42, for example, examines (calculates) the internal voltage phase angle difference of each generator based on the phase angle center of gravity of all generators 5, and determines that the generators 5 whose calculated phase angle difference does not exceed a predetermined designated value belong to the stable side system.

[0041] Here, since the stable side system is considered to be installed in a place away from the place where the assumed accident occurred in many cases, it may be considered that in most cases the system information of the stable side system cannot be directly measured by the information terminal 11. For this reason, it is difficult to measure the system information of the stable side system in real time immediately after the actual accident occurs.

[0042] As a countermeasure, in this embodiment, the stable side system model formulation unit 42 creates a regression model (function) indicating the relationship between the total load of the stable side system and the interconnection point bus voltage as a function for estimating the active power of the stable generator group model. As a result, the system information of the stable side system immediately after the occurrence of a fault is estimated using the regression model.

[0043] Moreover, the stable side system model formulation unit 42 calculates an inertia constant M2 of the stable generator group model as various constants for calculating the state quantities of the stable generator group model, as shown in (Equation 2).

[0044]

number

[0045] In (Equation 2), M2 is the inertia constant of the stable generator group model, M j indicates the inertia constant of the generator 5 with the identification number j belonging to the stable side system. The identification number j (j=0 to m) is a number that uniquely identifies a stable generator (a generator 5 belonging to the stable side system). m is an arbitrary natural number.

[0046] The discrimination criterion formulating unit 43 calculates a threshold value of the phase angle deviation Δδ of the integrated generator model (hereinafter, discrimination criterion value R). The discrimination criterion value R is used as a threshold value for discriminating the degree of stability after the occurrence of a fault by a stability discriminator 73 of the additional power control executing unit 50 described later.

[0047] The integrated generator model converts multiple generators into a single unit, and the phase angle deviation Δδ and the active power deviation ΔP G can be calculated using (Equation 3) to (Equation 12). The active power deviation ΔP of the integrated generator model is calculated from the unstable transient stability calculation result one step before the first number of shedding units that becomes stable and the stable transient stability calculation result. G and the phase angle deviation Δδ, and the effective power deviation ΔP immediately after the first shedding control in the stable case G The effective power deviation ΔP in the unstable case is G Increase the active power deviation ΔP G The phase angle deviation Δδ at the time when the active power deviation ΔP crosses zero after reaching a maximum is set as the discrimination criterion value R. The discrimination criterion value R is prepared for each fault condition. G The phase angle deviation Δδ at the maximum is stored.

[0048] More specifically, the phase angle deviation Δδ of the integrated generator model is calculated by (Equation 3).

[0049]

number

[0050] In (Equation 3), t indicates a predetermined time that has elapsed since the start of information collection, Δδ1 indicates the phase angle deviation of the unstable generator group model, and Δδ2 indicates the phase angle deviation of the stable generator group model.

[0051] Moreover, the phase angle deviation Δδ1 of the unstable generator group model is calculated based on (Equation 4) and (Equation 5).

[0052]

number

[0053]

number

[0054] In (Equation 4), δ1 represents the phase angle of the unstable generator group model. In (Equation 5), M i is the inertia constant of the generator 5 with the identification number i belonging to the unstable side system, and δ i indicates the phase angle of generator 5 with identification number i which belongs to the unstable side system.

[0055] Similarly, the phase angle deviation Δδ2 of the stable generator group model is calculated based on (Equation 6) and (Equation 7).

[0056]

number

[0057]

number

[0058] In (Equation 6), δ2 represents the phase angle of the stable generator group model. In (Equation 7), M j is the inertia constant of the generator 5 with the identification number j belonging to the stable side system, and δ j indicates the phase angle of generator 5 with identification number j that belongs to the stabilized side system.

[0059] In addition, the effective power deviation ΔP of the integrated generator model G is the inertia constant M1 of the unstable generator group model, the inertia constant M2 of the stable generator group model, and the active power deviation ΔP G1 , and the effective power deviation ΔP of the stable generator group model G2 It is calculated using (Equation 8).

[0060]

number

[0061] In addition, the effective power deviation ΔP G1 is calculated based on (Equation 9) and (Equation 10).

[0062]

number

[0063]

number

[0064] In (Equation 9), ΔP G1 is the active power deviation of the unstable generator group model, P G1 (t) is the active power of the unstable generator group model at a certain time t after the start of information collection, P G1 (0) indicates the active power of the unstable generator group model at the start of information collection (i.e., before the accident occurred). The active power P Gi (t) is the active power P of the generator 5 in the unstable side system at time t, as shown in (Equation 10). Gi Calculated by adding (t).

[0065] Similarly, the effective power deviation ΔP of the stable generator group model G1 is calculated based on (Equation 11) and (Equation 12).

[0066]

number

[0067]

number

[0068] In (Equation 11), ΔP G2 is the active power deviation of the stable generator group model, P G2 (t) is the active power of the stable generator group model at a certain time t after the start of information collection, P G2 (0) indicates the active power of the stable generator group model at the start of information collection (i.e., before the accident occurred). The active power P G2 (t) is the active power P of the generator 5 in the stable side system at time t, as shown in (Equation 12). Gi It is defined as the sum of (t).

[0069] The output change model formulation unit 44 uses the calculation results stored in the calculation result storage unit 37 to calculate the active power deviation ΔP G The coefficient for determining the change in the active power deviation ΔP is calculated in advance. G The change in the output is a step-like change immediately after the implementation of shedding control. The output change model formulation unit 44 further obtains the short-circuit impedance to other unstable generators and the short-circuit impedance to stable generators as viewed from the terminal bus of the additional shedding controlled generator in the total shedding control pattern in which each candidate additional shedding controlled generator is added to the first shedding controlled generator, and calculates a ratio with the sum of the two short-circuit impedances as the denominator and the short-circuit impedance to the stable generator as the numerator.

[0070] As another method, the output change model formulation unit 44 performs a transient stability calculation for all the shedding control patterns in which each candidate for additional shedding control generators is added to the first shedding control generator, and calculates the active power deviation ΔP from the calculation result. G There is also a method to find the change in

[0071] The model information formulated by the unstable side system model formulating unit 41, the stable side system model formulating unit 42, and the output change model formulating unit 44 is an example of "model definition information".

[0072] The correction coefficient generating unit 80 includes a stability limit correction ratio calculating unit 81, an active power deviation correction value function calculating unit 82, and an electric torque conversion value function calculating unit 83. The correction coefficient generating unit 80 performs processing at the same cycle as the selection of the first electrical control, regardless of whether or not an accident has occurred.

[0073] The stability limit correction ratio calculation unit 81 uses the calculation results stored in the calculation result storage unit 37 to calculate a ratio to be used in a phase angle deviation second coefficient calculation unit 92, which will be described later.

[0074] 2 is a diagram showing an example of a calculation result used in the process performed by the stability limit correction ratio calculation unit 81. In FIG. 2, the active power deviation ΔP G 2, a locus A shows an example of the relationship between the active power deviation ΔP G and phase angle deviation Δδ. Trajectory B is the active power deviation ΔP from the first shedding control of trajectory A. G Using the trajectory up to the maximum point as a training data, the formula (ΔP G = a1·sin(Δδ+b1)+c1) is used as an approximation. G ΔP to the right of the maximum point G The coefficient a1 of the formula for trajectory B is adjusted so that it is equal to the area of ​​the active power deviation ΔP G is the phase angle deviation Δδ at the time when the phase crosses zero.

[0075] The stability limit correction ratio calculation unit 81 calculates a ratio to be used in a phase angle deviation second coefficient calculation unit 92, which will be described later, using the phase angle deviations ΔδA, ΔδB, and ΔδC shown in Fig. 2 and (Equation 13). However, if the magnitude relationship ΔδA>ΔδC>ΔδB does not hold, the ratio is set to 0.

[0076]

number

[0077] The active power deviation correction value function calculation unit 82 uses the calculation results stored in the calculation result storage unit 37 to calculate coefficients of an approximation function used in an active power deviation correction value calculation unit 93 described later.

[0078] 3 is a diagram for explaining an example of the process performed by the active power deviation correction value function calculation unit 82. In FIG. G 3 shows an example of a time series change in the phase angle deviation Δδ. In FIG. 3(a), the stable trajectory is a trajectory of the result of stable shearing conditions among the calculation results stored in the calculation result storage unit 37. The unstable trajectory is a trajectory of the unstable result of shearing conditions that are one step lower than the shearing results of the stable shearing conditions. The composite trajectory is a trajectory obtained by combining the stable trajectory and the unstable trajectory. The active power deviation correction value function calculation unit 82 uses the stable trajectory and the unstable trajectory to calculate the active power deviation ΔP up to the time when the phase angle deviation Δδ is maximum in the stable result. G >0, the stable and unstable active power deviation ΔP G The active power deviation correction value function calculation unit 82 calculates the trajectory of the tangent from the composite trajectory and obtains the coefficient of a linear function (difference = a2 · elapsed time + b2) equivalent to the difference between the two. FIG. 3(b) shows an example of the trajectory of the tangent from the composite trajectory calculated by the active power deviation correction value function calculation unit 82. For example, in the composite trajectory, the active power deviation correction value function calculation unit 82 calculates the active power deviation ΔP GAfter rising once, it becomes unstable and starts to fall (0.45 [seconds] in Figure 3), and after that, the active power deviation ΔP G The coefficient of the tangent locus (linear function) is calculated starting from the time when the downward slope of the curve becomes gentler (i.e., the time of the inflection point of the composite trajectory (0.58 seconds in Figure 3)).

[0079] The electric torque conversion value function calculation unit 83 calculates coefficients of an approximation function used by an electric torque conversion correction value calculation unit 91, which will be described later, using the calculation results stored in the calculation result storage unit 37. The approximation function calculates a correction value for correcting the active power deviation into an electric torque deviation.

[0080] FIG. 4 is a diagram illustrating an example of the difference between the active power and the electric torque. G An example of the time series change of the active power deviation ΔP G As shown in Fig. 4(a), the active power deviation ΔP G Furthermore, even after the fault is cleared and before and after the first shedding, the active power deviation ΔP G Therefore, as shown in FIG. 4(b), the effective power deviation ΔP G The difference between the active power deviation ΔP also changes before the fault occurs, during the fault, after the fault is cleared, and before and after the first power control. G The difference after the fault is cleared is correlated with the phase angle deviation Δδ. Therefore, the electric torque conversion value function calculation unit 83 defines functions separately for during the fault and after the fault is cleared. The function during the fault is the correction value = a3 ΔP G +b3, and the function after the fault is removed is correction value = a4·Δδ+b4·ΔP GI +c4, where ΔP GI is the effective power deviation ΔP due to the first shedding control GAmong the transient stability calculation results stored in the calculation result storage unit 37, the calculation result showing instability under the shedding condition that is one step lower than the stable shedding condition is used to find the difference between the active power and the electric torque of the integrated generator model, and the coefficients of the approximation function are calculated using the difference as a teacher.

[0081] The above-mentioned information required for calculating and estimating the phase angle deviation Δδ of the integrated generator model, which is formulated by the stability limit correction ratio calculation unit 81, the active power deviation correction value function calculation unit 82, and the electric torque conversion value function calculation unit 83, is an example of the “correction preparation information”.

[0082] The additional power control execution unit 50 is a functional unit that operates after an accident occurs in the power system. When an accident occurs in the power system, the additional power control execution unit 50 determines whether or not to perform additional power control after performing power control by the first power control machine by using functions and the like generated by the stability evaluation model generation unit 40 and the correction coefficient generation unit 80, and if additional power control is necessary, selects the target power control machine.

[0083] The additional power control execution unit 50 includes a high-speed information collection unit 51, a generator state calculation unit 60, an output change estimation unit 71, a discrimination criteria adjustment unit 72, a stability discrimination unit 73, an additional power control unit selection unit 74, and a generator state correction unit 90.

[0084] The high-speed information collection unit 51 acquires system information via the transmission system 10 at a sampling period (for example, on the order of milliseconds) faster than the period for acquiring system information by the power control execution unit 30. The system information here includes various information such as generator active power, transmission line active power, phase angle difference between the interconnection point and each generator, voltage at the interconnection point, and active power of the interconnection line. The high-speed information collection unit 51 constantly collects system information at a high-speed sampling period and writes it into a buffer memory, and holds system information for a certain time period so that it can be referenced. When the high-speed information collection unit 51 determines that an accident has occurred, it extracts system information collected during a certain time period from a predetermined time before the accident occurred (hereinafter referred to as the start time of information collection) until a predetermined time has elapsed (hereinafter referred to as the end time of information collection). The high-speed information collection unit 51 outputs the extracted system information for the certain time period to the generator state calculation unit 60.

[0085] The occurrence of an accident can be determined by acquiring the operation signal of a protective relay. For example, one of the protective relays measures the currents at both ends of a power transmission line and determines whether the difference between them is equal to or greater than a predetermined threshold. In this case, if the current difference is equal to or greater than the predetermined threshold, it is determined that an accident has occurred.

[0086] The generator state calculation unit 60 calculates the state of the generator 5 after the occurrence of the accident by using the system information acquired from the high-speed information collection unit 51. The state of the generator 5 is, for example, the active power deviation ΔP G , and the phase angle deviation Δδ. G is the time series change in active power from the start of information collection to the end of information collection, with the active power before the fault as the reference. Phase angle deviation Δδ is the time series change in phase angle from the start of information collection to the end of information collection, with the phase angle before the fault as the reference.

[0087] The generator state calculation unit 60 includes an unstable generator calculation unit 61, a stable generator calculation unit 62, a phase angle deviation calculation unit 63, a phase angle deviation coefficient calculation unit 64, an adjustment necessity determination unit 65, and a phase angle deviation estimation unit 66. In addition, the generator state correction unit 90 includes an electric torque conversion correction value calculation unit 91, a phase angle deviation second coefficient calculation unit 92, an active power deviation correction value calculation unit 93, and a phase angle deviation re-estimation unit 94.

[0088] The unstable generator calculation unit 61 calculates the active power deviation ΔP of the unstable generator group model at a predetermined interval (for example, 10 millisecond interval) during the measurement period from the occurrence of the fault to the end of information collection based on the various constants calculated by the unstable side system model formulation unit 41 and the information collected by the high-speed information collection unit 51. G1 The predetermined interval depends on the period in which the high speed information collector 51 collects information.

[0089] Specifically, the unstable generator calculation unit 61 calculates the active power deviation of the unstable generator group model by subtracting the active power of the unstable generator group model before the accident occurs from the active power of the unstable generator group model at time t, as shown in (Equation 14).

[0090]

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[0091] In (Equation 14), ΔP G1 is the active power deviation of the unstable generator group model, P G1 (t) is the active power of the unstable generator group model at a certain time t after the start of information collection, P G1 (0) indicates the active power of the unstable generator group model at the start of information collection (i.e., before the accident occurs).

[0092] The unstable generator calculation unit 61 calculates the effective power P G1 (t) is expressed as the active power P GiCalculated by adding (t).

[0093]

number

[0094] The stable generator calculation unit 62 calculates the active power deviation ΔP of the stable generator group model at a predetermined interval (for example, 10 millisecond interval) during the measurement period from the occurrence of the fault to the end of information collection, based on the function and various constants obtained by the stable side system model formulation unit 42 and the information collected by the high-speed information collection unit 51. G2 This interval depends on the period at which the high-speed information collector 51 collects information, as in the case of the unstable generator calculator 61.

[0095] Specifically, the stable generator calculation unit 62 calculates the active power deviation of the stable generator group model by subtracting the active power of the stable generator group model before the accident occurs from the active power of the stable generator group model at time t, as shown in (Equation 16).

[0096]

number

[0097] In (Equation 16), ΔP G2 is the active power deviation of the stable generator group model, P G2 (t) is the active power of the stable generator group model at a certain time t after the start of information collection, P G2 (0) indicates the active power of the stable generator group model at the start of information collection (i.e., before the accident occurred).

[0098] Active power P of the stable generator group model G2 (t) is the active power P of the generator 5 in the stable side system at time t, as shown in (Equation 17). Gi It is defined as the sum of (t).

[0099]

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[0100] In actual calculation, the stabilized generator calculation unit 62 estimates the total load in the stabilized side system by inputting the interconnection point bus voltage collected by the high-speed information collection unit 51 into the regression model constructed by the stabilized side system model formulation unit 42, and may take the difference between the measured active power flowing to the stabilized side system and the estimated total load as the sum of the generator active powers of the stabilized side system.The stabilized generator calculation unit 62 then adds the measured value of the active power of the stabilized generators of the internal system to the sum of the generator active powers of the stabilized side system to calculate the active power P G2 Let us assume that.

[0101] The phase angle deviation calculation unit 63 calculates the effective power deviation ΔP of the unstable generator group model calculated by the unstable generator calculation unit 61. G1 and the effective power deviation ΔP of the stable generator group model calculated by the stable generator calculation unit 62 G2 and (Equation 18), the phase angle deviation Δδ of the integrated generator model in the measurement period from the occurrence of the accident to the end of information collection by the high-speed information collection unit 51 is calculated. In (Equation 18), C1(t) is a correction value for converting the active power deviation into an equivalent electric torque deviation, which is calculated by an electric torque conversion correction value calculation unit 91 described later.

[0102]

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[0103] In (Equation 18), M is the inertia constant of the generator, ω0 is the fundamental angular frequency (constant), and ΔP G indicates the active power deviation of the integrated generator model. The inertia constant M is calculated by (Equation 19) using the inertia constant M1 of the unstable generator group model and the inertia constant M2 of the stable generator group model.

[0104]

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[0105] In addition, the effective power deviation ΔP of the integrated generator modelG is the inertia constant M1 of the unstable generator group model, the inertia constant M2 of the stable generator group model, and the active power deviation ΔP G1 , and the effective power deviation ΔP of the stable generator group model G2 It is calculated using (Equation 20).

[0106]

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[0107] In addition, (Equation 18) is expressed as the equation of motion shown in (Equation 21) with the damping coefficient D set to 0 and the mechanical input T m The electric torque T before the accident occurred G The result was (0).

[0108]

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[0109] The phase angle deviation coefficient calculation unit 64 calculates the phase angle deviation Δδ of the integrated generator model during the measurement period calculated by the phase angle deviation calculation unit 63 and the active power deviation ΔP G Based on this, the active power deviation ΔP G and the phase angle deviation Δδ. S Calculate.

[0110]

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[0111] In (Equation 22), α is the effective power deviation ΔP G is the difference between the phase angle deviation Δδ at which the phase angle is maximized and π / 2 [rad], and is calculated in advance by the discrimination criterion formulation unit 43.

[0112] The adjustment necessity determination unit 65 determines whether or not the difference α in equation (22) needs to be adjusted based on the information collected by the high-speed information collection unit 51. When it is determined that adjustment is necessary, a preset value is subtracted from α, and the result is set as a new α. The difference α is determined to need adjustment when Y in equation (23) is equal to or smaller than a predetermined threshold value.

[0113]

number

[0114] In (Equation 23), Y B indicates the evaluation index of the external system reactance corresponding to the previous calculation, and Y A Y indicates the evaluation index of the external system reactance based on the measured values ​​before and after the fault occurs. B According to (Equation 24), Y A is calculated by (Equation 25).

[0115]

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[0116]

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[0117] Furthermore, X in (Equation 24) B (t) is calculated by (Eq. 26) as follows: B (0) is calculated by (Equation 27). Also, X in (Equation 25) A (t) is calculated by (Eq. 28) as follows: A (0) is calculated by (Equation 29).

[0118]

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[0119]

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[0120]

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[0121]

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[0122] In (Equation 26) to (Equation 29), δ(0) is the initial phase angle value converted into the integrated generator model obtained from the previous calculation result, Δδ is the phase angle deviation converted into the integrated generator model, P is the active power of the interconnection line, and V is the bus voltage at the interconnection point. In addition, the subscript B represents the result of the previous calculation and the calculated value using that result, and A represents the measured value and the calculated value using the measured value.

[0123] The phase angle deviation estimation unit 66 estimates the active power deviation ΔP of the integrated generator model immediately after the first shedding control, which reflects the influence of the first shedding control calculated by the output change estimation unit 71 described later. G Starting from the above, the phase angle deviation Δδ (future value) of the integrated generator model for each time step after the first shedding control is calculated by iterative time series calculation using the above-mentioned (Equation 18), (Equation 22), and (Equation 30). Note that the inertia constant M in (Equation 18) is a value obtained by deducting the value for the generator selected in the first shedding control. Furthermore, when additional shedding control is implemented after the first shedding control, the phase angle deviation estimation unit 66 calculates the active power deviation ΔP G The change in the active power deviation ΔP of the integrated generator model at the time of additional shedding is G The phase angle deviation Δδ (future value) of the integrated generator model after the additional shedding control is calculated by iterative time series calculation using (Equation 18), (Equation 22), and (Equation 30). In this case, the inertia constant M in (Equation 18) is a value obtained by subtracting the value for the generators selected in the first shedding control and additional shedding control.

[0124] In addition, the effective power deviation ΔP G The estimated calculation of the effective power deviation ΔP GUp to the maximum point, the phase angle deviation calculation unit 63 uses the above-mentioned (Equation 22), and after the maximum point, (Equation 30) is used. The difference between (Equation 22) and (Equation 30) is the coefficient K calculated by the phase angle deviation coefficient calculation unit 64. S and the coefficient K calculated by the phase angle deviation second coefficient calculation unit 92 described later. S2 The difference is whether to use

[0125]

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[0126] An electric torque conversion correction value calculation unit 91 calculates a correction value C1(t) using an approximation function of the coefficients calculated by the electric torque conversion value function calculation unit 83. The correction value C1 is an example of a "first correction value."

[0127] The phase angle deviation second coefficient calculation unit 92 calculates the phase angle deviation ΔδC′ calculated using the ratio obtained by the stability limit correction ratio calculation unit 81 and the effective power deviation ΔP obtained by the processing of the phase angle deviation estimation unit 66. G The coefficient K in (Equation 30) is calculated from the two points, the maximum value and the phase angle deviation Δδ at that time. S2 The phase angle deviation ΔδC' is calculated by the ratio (Δδ S -ΔδB') + ΔδB', where Δδ S is the stability determination threshold, and ΔδB' is the coefficient K obtained by the phase angle deviation coefficient calculation unit 64. S Calculated using ΔP G = 0. The coefficient K S2 is an example of a "second coefficient."

[0128] The active power deviation correction value calculation unit 93 calculates a correction value C2(t) using an approximation function of the coefficients calculated by the active power deviation correction value function calculation unit 82. The correction value C2 is an example of a "second correction value."

[0129] The phase angle deviation re-estimation unit 94 estimates the effective power deviation ΔP of the integrated generator model calculated by the phase angle deviation estimation unit 66. Gand (Equation 31), the phase angle deviation Δδ of the integrated generator model is recalculated. The difference between (Equation 31) and (Equation 18) is that the correction value C2(t) calculated by the active power deviation correction value calculation unit 93 is newly added. The inertia constant M in (Equation 31) is changed according to the power control conditions, as in the phase angle deviation estimation unit 66.

[0130]

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[0131] The output change estimation unit 71 estimates the effective power deviation ΔP of the integrated generator model when the first power control is performed, which is previously calculated by the output change model formulation unit 44. G The change in the active power deviation ΔP G The output change estimation unit 71 also multiplies the ratio of the short-circuit impedance obtained from the output change model formulation unit 44 by the active power before the fault of the additional shedding unit selected by the additional shedding unit selection unit 74 described later, to obtain the active power deviation ΔP G Find the change in .

[0132] The discrimination criterion adjustment unit 72 adjusts the discrimination criterion value R obtained by the discrimination criterion formulation unit 43 as necessary. First, the discrimination criterion adjustment unit 72 obtains the measured value of the phase angle difference between the interconnection point and each unstable generator before the occurrence of the accident from the high-speed information collection unit 51, and obtains the phase angle difference between the interconnection point and each unstable generator in the previous calculation from the calculation result storage unit 37. Next, for each generator, the difference between the phase angle difference of the measured value and the phase angle difference of the previous calculation is taken, and one phase angle difference is obtained by inertia weighted averaging. Then, if this phase angle difference is a positive value, that is, if the phase angle difference of the measured value is larger than that of the previous calculation, twice the value of the phase angle difference obtained by the inertia weighted averaging is subtracted from the discrimination criterion value R obtained by the discrimination criterion formulation unit 43 to obtain a new discrimination criterion value R. As a result, if the phase angle difference of the measured value is larger than that of the previous calculation, the discrimination criterion value R becomes smaller, making it easier to determine that the system is unstable, and reducing the number of times that instability is erroneously determined as stable.

[0133] The stability discrimination unit 73 compares the phase angle deviation Δδ of the integrated generator model estimated by the phase angle deviation re-estimation unit 94 with the discrimination reference value R obtained from the discrimination reference adjustment unit 72. The stability discrimination unit 73 discriminates the phase angle deviation Δδ as stable when the maximum value of the phase angle deviation Δδ is below the discrimination reference value R, and discriminates the phase angle deviation Δδ as unstable when the maximum value of the phase angle deviation Δδ is below the discrimination reference value R.

[0134] The additional shedding control machine selection unit 74 selects an additional shedding control machine from among the additional shedding control candidates based on the coefficients calculated by the output change model formulation unit 44, and determines the effective power deviation ΔP G The additional shedding control machine selection unit 74 selects the machine with the largest change in short-circuit impedance obtained from the output change model formulation unit 44 as the additional shedding control machine. Note that stability determination may be performed for all combinations of additional shedding control candidates, and an additional shedding control machine with the smallest shedding amount may be selected from among the stable combinations. As another method, the active power deviation ΔP of the additional shedding control candidate obtained by the transient stability calculation in the output change model formulation unit 44 may be used. G The change in may be used.

[0135] [Additional power control execution unit processing] 5 is a flowchart showing an example of the flow of processing performed by the additional power control executing unit 50. More specifically, in the case where an accident occurs in the power system, the additional power control executing unit 50 determines whether or not to perform additional power control after performing power control by the first power control machine by using functions and the like generated by the stability evaluation model generating unit 40 and the correction coefficient generating unit 80, and if additional power control is necessary, selects the target power control machine.

[0136] First, the high-speed information collector 51 collects system information for a specified fixed time period from system information previously collected at a high-speed sampling period (step S1).

[0137] Next, the unstable generator calculation unit 61 calculates the active power deviation ΔP of the unstable generator group model during the measurement period from the occurrence of the fault to the end of information collection based on the various constants calculated by the unstable side system model formulation unit 41 and the information collected by the high-speed information collection unit 51.G1 Calculate (step S2).

[0138] Next, the stable generator calculation unit 62 calculates the active power deviation ΔP of the stable generator group model during the measurement period based on the function and various constants obtained by the stable side system model formulation unit 42 and the information collected by the high-speed information collection unit 51. G2 is estimated (step S3).

[0139] Next, the phase angle deviation calculation unit 63 calculates the effective power deviation ΔP of the unstable generator group model calculated by the unstable generator calculation unit 61. G1 and the effective power deviation ΔP of the stable generator group model calculated by the stable generator calculation unit 62 G2 Based on this, the phase angle deviation Δδ of the integrated generator model during the measurement period is calculated (step S4). The calculation formulas are the above-mentioned (Formula 18) and (Formula 20). (Formula 18) includes a correction value C1 calculated by the electric torque conversion correction value calculation unit 91 using the approximation function obtained by the electric torque conversion value function calculation unit 83 and the phase angle deviation Δδ of the integrated generator model of the previous step, etc.

[0140] Next, the phase angle deviation coefficient calculation unit 64 calculates the phase angle deviation Δδ of the integrated generator model during the measurement period calculated by the phase angle deviation calculation unit 63 and the active power deviation ΔP G Based on this, the effective power deviation estimation coefficient K S is calculated (step S5).

[0141] Next, the adjustment necessity determination unit 65 determines whether or not the estimation coefficient needs to be adjusted based on whether or not Y in (Equation 23) is equal to or less than a predetermined threshold (step S6). If Y is equal to or less than the predetermined threshold, the adjustment necessity determination unit 65 determines that adjustment is necessary, and, for example, subtracts a preset value from α and sets the result as a new α.

[0142] Next, the output change estimation unit 71 calculates the effective power deviation ΔP of the integrated generator model when the first power control is performed, which is previously calculated by the output change model formulation unit 44. GThe change in the active power deviation ΔP G (step S7).

[0143] Next, the phase angle deviation estimator 66 calculates the active power deviation ΔP of the integrated generator model immediately after the first shedding control, which reflects the influence of the first shedding control calculated by the output change estimator 71. G Starting from the first shedding event, the active power deviation ΔP of the integrated generator model is calculated by iteratively calculating the time series using the above (Equation 18) and (Equation 22). G The phase angle deviation Δδ of the integrated generator model for each time step is calculated up to the maximum point (step S8). The above-mentioned (Equation 18) includes the correction value C1 calculated by the electric torque conversion correction value calculation unit 91 for converting the active power deviation into an electric torque deviation. Since the correction value C1≧0, the active power deviation ΔP G Since increases, the phase angle deviation Δδ of the integrated generator model becomes smaller.

[0144] Next, the phase angle deviation second coefficient calculation unit 92 calculates the ratio calculated by the stability limit correction ratio calculation unit 81 and the active power deviation ΔP G and the phase angle deviation Δδ, the effective power deviation P G Coefficient K for estimating after the maximum point S2 Calculate (step S9).

[0145] Next, the phase angle deviation estimation unit 66 obtains the phase angle deviation Δδ of the integrated generator model in the same manner as in step S8 (step S10). G The estimation calculation of is performed using the coefficient K calculated by the phase angle deviation second coefficient calculation unit 92. S2 The coefficient K S ≦Coefficient K S2 From the relationship between the two, compared to the conventional grid stabilization system that implements the second shedding control, the effective power deviation ΔP G Since increases, the phase angle deviation Δδ of the integrated generator model becomes smaller.

[0146] Next, the active power deviation correction value calculation unit 93 calculates the correction value C2(t) by using an approximation function of the coefficients calculated by the active power deviation correction value function calculation unit 82 (step S11).

[0147] Next, the phase angle deviation re-estimation unit 94 calculates the active power deviation ΔP of the integrated generator model calculated by the phase angle deviation estimator 66 in steps S8 and S10. G and (Equation 31), the phase angle deviation Δδ is recalculated (step S12). Because correction value C2>0, when compared at the same time, the phase angle deviation Δδ recalculated by phase angle deviation re-estimation unit 94 is smaller than the phase angle deviation Δδ calculated by phase angle deviation estimator 66. Since the phase angle deviation Δδ is determined to be unstable when it exceeds the threshold value, a smaller phase angle deviation Δδ means that the possibility of being determined to be stable increases.

[0148] Next, the discrimination criterion adjustment unit 72 determines whether the phase angle difference calculated by the above-mentioned single inertia weighted average is a positive value, and if it is a positive value, subtracts twice the phase angle difference from the discrimination criterion value R calculated by the discrimination criterion formulation unit 43 to obtain a new discrimination criterion value R (step S13).

[0149] Next, the stability discriminator 73 compares the phase angle deviation Δδ of the integrated generator model estimated by the phase angle deviation estimator 66 with the discrimination reference value R obtained from the discrimination reference adjuster 72. The stability discriminator 73 discriminates the phase angle deviation Δδ as stable when the maximum value of the phase angle deviation Δδ is below the discrimination reference value R, and discriminates the phase angle deviation Δδ as unstable when the maximum value of the phase angle deviation Δδ is above the discrimination reference value R (step S14).

[0150] When the stability determination unit 73 determines that the power supply is unstable, the additional shedding control unit selection unit 74 selects an additional shedding control unit from among the additional shedding control candidates based on the coefficients calculated by the output change model formulation unit 44, and calculates the effective power deviation ΔP G The generator with the largest change is selected as the additional shear generator (step S15).

[0151] Next, the output change estimation unit 71 multiplies the ratio of the short-circuit impedance obtained from the output change model formulation unit 44 by the active power before the fault of the additional shedding unit selected in step S15 to obtain the active power deviation ΔP of the integrated generator model. G Alternatively, the active power deviation ΔP due to the additional power control obtained from the output change model formulation unit 44 is defined as the change in the active power deviation ΔP G The change in is used.

[0152] Next, the phase angle deviation estimator 66 estimates the effective power deviation ΔP G The change in the active power deviation ΔP of the integrated generator model at the time of additional shedding is G The phase angle deviation Δδ of the integrated generator model after the additional shedding control is calculated by iterative calculation of the time series using the above-mentioned (Equation 18), (Equation 22), and (Equation 30) (Step S17). At this time, the active power deviation ΔP G Up to the maximum point, the active power deviation ΔP G To calculate the effective power deviation ΔP, use (Equation 22). G After the maximum point, the effective power deviation ΔP G To calculate this, use (Equation 30).

[0153] Next, the phase angle deviation re-estimation unit 94 calculates the effective power deviation ΔP of the integrated generator model calculated by the phase angle deviation estimator 66 in step S17. G The phase angle deviation Δδ is recalculated using (Equation 31) (step S18). Since the correction value C2>0, when compared at the same time, it is smaller than the phase angle deviation Δδ calculated by the phase angle deviation estimation unit 66.

[0154] Thereafter, the phase angle deviation re-estimator 94 returns the process to step S14.

[0155] If the stability determination unit 73 determines that the generator is stable, the additional power control execution unit 50 transmits a shutoff command to the control terminal 12 of the additional power control machine selected by repeating steps S15 to S18, and disconnects the corresponding generator from the power grid (step S19). If the processing from step S15 to step S18 is not performed and the processing proceeds to step S19, an additional power control machine has not been selected. In that case, the additional power control execution unit 50 does not transmit a shutoff command to the control terminal 12 of any of the generators.

[0156] Fig. 6 is a diagram for explaining an example of processing performed by the additional shedding control execution unit 50. Fig. 6 shows time series changes in the active power deviation and phase angle deviation of the generator 5, with time t0 indicating the start of information collection (before the accident), time t1 indicating the occurrence of the accident (occurrence of the accident), time t2 indicating the removal of the accident (removal of the accident), time t3 indicating the end of information collection (end of measurement), time t4 indicating the execution of shedding control by the first shedding control machine (first shedding control), and time t5 indicating the execution of additional shedding control (additional shedding control).

[0157] Figure 6 (a) shows the effective power deviation ΔP G2 At time t1 when the fault occurred, the active power deviation ΔP G2 However, after the fault was removed at time t2, the effective power deviation ΔP G2 The active power deviation ΔP of the unstable generator group model is increasing. G1 At time t1, the active power deviation ΔP G1 After time t2, the active power deviation ΔP G2 and the active power deviation ΔP G1 and the active power deviation ΔP of the integrated generator model obtained by (Equation 14) G The active power deviation ΔP G1 Similarly, the effective power deviation ΔP Galso dropped significantly at time t1, and increased slightly after time t2, but then started to drop again. Figure 6(d) shows the change in the phase angle deviation Δδ of the integrated generator model, obtained by subtracting the phase angle deviation Δδ2 of the stable generator group model from the phase angle deviation Δδ1 of the unstable generator group model. After time t1, the phase angle deviation Δδ increases monotonically.

[0158] The above explanation is for the transitions before time t3 when the measurement ends, but the transitions after time t3 are predicted to change depending on whether or not shearing control is performed. Specifically, we will explain the predicted transitions of the active power deviation and phase angle deviation for each of the cases: (A) when shearing control is not performed, (B) when only the first shearing control is performed, and (C) when additional shearing control is performed.

[0159] (A) When no power control is implemented, after time t3, the phase angle deviation Δδ increases monotonically beyond the discrimination reference value R, as shown by the dashed line in (d) of Figure 6, and the active power deviation ΔP G is predicted to deviate from zero and decrease monotonically. In this case, the active power deviation ΔP G As shown by the dashed line in Fig. 6(c), it is predicted that the slope of the increase in the phase angle deviation Δδ will continue to decrease, although the slope will become somewhat gentler. For this reason, (A) not implementing shedding control is not preferable. (B) When only the first shedding control is implemented, the slope of the increase in the phase angle deviation Δδ will decrease at time t4, and the active power deviation ΔP G is predicted to take a positive value. However, the phase angle deviation Δδ still increases monotonically beyond the discrimination criterion value R, and accordingly, the active power deviation ΔP G is predicted to deviate from zero and decrease monotonically. In this case, the active power deviation ΔP G is the active power deviation ΔP shown by the dashed line in Fig. 6(c). G As shown in Fig. 1, although the first shedding control temporarily makes the active power deviation Δδ greater than zero, it is predicted that the active power deviation ΔP will continue to decrease and eventually become zero or less. For this reason, it is not preferable to implement only the first shedding control (B). In the case of implementing additional shedding control (C), at time t5, the phase angle deviation Δδ will start to decrease and the active power deviation ΔP Gis predicted to remain positive and not deviate from zero even after time t5. At this time, the active power deviation ΔP G is the active power deviation ΔP shown by the two-dot chain line in Fig. 6(c). G " As a result of the additional power cut, the power output will increase more than with the first power cut, and then decrease in the same way as with the first power cut, but it is predicted that the time it takes for the power output to drop below zero can be extended. For this reason, it is preferable to implement (C) additional power cut.

[0160] According to at least one embodiment described above, the time transition of the phase angle deviation of the integrated generator model in which the entire power system is converted into one generator is calculated using functions and coefficients prepared in advance based on the calculation results of the transient stability calculation, and measurement information of the power system and the generator before and after the occurrence of the accident, and the time transition of the phase angle deviation reflecting the first shearing control is estimated to perform a stability determination. When it is determined that the generator is in an unstable state in which it will step out, the selection of an additional shearing control machine, the estimation of the time transition of the phase angle deviation reflecting the additional shearing control, and the stability determination are repeated to select an additional shearing control machine that will be stable, and by cutting off the additional shearing control machine from the power system following the first shearing control, it is possible to maintain a stable state in which the generator does not step out even if the first shearing control causes instability. In addition, the active power deviation ΔP of the integrated generator model G The electric torque deviation ΔT required for the original calculation formula G The introduction of a correction value C1 that corrects the phase angle deviation Δδ of the integrated generator model and the effective power deviation ΔP G The coefficient for estimating the effective power deviation ΔP G The second coefficient K is used to reflect the difference between the maximum and the other maximum points. S2 Calculate and switch the active power deviation ΔP over time, in addition to the correlation with the phase angle deviation Δδ. G By introducing the correction value C2 to reflect the increase in, it is possible to prevent a stable state from being erroneously determined to be unstable.

[0161] In the above embodiment, an example was shown in which stability was determined using the phase angle deviation Δδ of the integrated generator model, but stability may be determined using a phase angle δ obtained by adding the initial phase angle value before the occurrence of the accident to the phase angle deviation. In that case, the discrimination criterion obtained by the discrimination criterion formulation unit 43 is also the one to which the initial phase angle value has been added.

[0162] In the above embodiment, an example has been shown in which information collection by the high-speed information collection unit 51 ends before the first power control is implemented, but information collection by the high-speed information collection unit 51 may also be performed after the first power control is implemented. In that case, the active power deviation of the unstable generator group model due to the first power control is calculated based on information from the high-speed information collection unit 51.

[0163] In the above embodiment, an example has been shown in which the change in the active power deviation due to the first shearing control is reflected and the phase angle deviation after the first shearing control is calculated based on the change. However, when the change to be reflected is extremely small, such as when the change is zero, it is not necessary to reflect the change due to the first shearing control and to calculate the phase angle deviation. In that case, only the additional shearing control may be executed without executing the first shearing control.

[0164] In the above embodiment, the amount of power control when additional power control is performed is calculated by multiplying the coefficient K S2 In the above description, the correction is performed based on the correction value C2 calculated by the active power deviation correction value calculation unit 93 using the coefficient of the approximation function calculated by the active power deviation correction value function calculation unit 82, and the correction value C1 calculated by the electric torque conversion correction value calculation unit 91 using the coefficient of the approximation function calculated by the electric torque conversion value function calculation unit 83. However, the amount of power control when additional power control is performed does not need to be corrected using all of these three values. In other words, the amount of power control when additional power control is performed is determined based on the coefficient K calculated by the phase angle deviation second coefficient calculation unit 92. S2The correction may be performed using one or two of the correction value C2 calculated by the active power deviation correction value calculation unit 93 and the correction value C1 calculated by the electric torque conversion correction value calculation unit 91. In this case, the power grid stabilization system 20 may omit a component for calculating a value that does not correct the amount of power control in the additional power control. That is, in the power grid stabilization system 20, the coefficient K S2 In the case where the power control amount of the additional power control is not corrected using the correction value C2 in the power grid stabilization system 20, the active power deviation correction value function calculation unit 82 and the active power deviation correction value calculation unit 93 may be omitted. In the case where the power control amount of the additional power control is not corrected using the correction value C1 in the power grid stabilization system 20, the electric torque conversion value function calculation unit 83 and the electric torque conversion correction value calculation unit 91 may be omitted.

[0165] Although some 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 in the scope of the invention and its equivalents described in the claims, as well as in the scope and spirit of the invention. [Explanation of symbols]

[0166] 1···Power system, 2, 2-1, 2-2, 2-3, 2-4, 2-5···Busbar, 3, 3-1, 3-2, 3-3, 3-4, 3-5···Transmission line, 4, 4-1, 4-2, 4-3, 4-4···Transformer, 5, 5-1, 5-2, 5-3, 5-4···Generator, 6, 6-1, 6-2, 6-3, 6-4···Circuit breaker, 11, 11-1, 11-2, 11-3, 11-4, 11-5··Information terminal, 12, 12-1, 12 -2... Control terminal, 10... Transmission system, 20... Power system stabilization system, 30... Power control execution unit, 31... Power system information collection unit, 32... Basic power system memory unit, 33... Power system model creation unit, 34... Stability calculation unit, 35... Power control unit selection unit, 36... First-stage power control unit, 37... Calculation result memory unit, 40... Stability evaluation model generation unit, 41... Unstable side power system model formulation unit, 42... Stable side power system model formulation unit, 43...discrimination criterion formulation unit, 44...output change model formulation unit, 50...additional shedding control execution unit, 51...high-speed information collection unit, 60...generator state calculation unit, 61...unstable generator calculation unit, 62...stable generator calculation unit, 63...phase angle deviation calculation unit, 64...phase angle deviation coefficient calculation unit, 65...adjustment necessity determination unit, 66...phase angle deviation estimation unit, 71...output change estimation unit, 72...discrimination criterion adjustment unit, an adjustment unit, 73...stability determination unit, 74...additional shear unit selection unit, 80...correction coefficient generation unit, 81...stability limit correction ratio calculation unit, 82...active power deviation correction value function calculation unit, 83...electrical torque conversion value function calculation unit, 90...generator state correction unit, 91...electrical torque conversion correction value calculation unit, 92...phase angle deviation second coefficient calculation unit, 93...active power deviation correction value calculation unit, 94...phase angle deviation re-estimation unit

Claims

1. A system stabilization system that collects system information including at least active and reactive power of transmission lines that constitute a power system, constructs a system model, and performs transient stability calculations for assumed accident conditions in advance to select a first electrically controlled generator for preventing a generator from losing synchronism for each assumed accident condition, and prevents loss of synchronism by disconnecting the first electrically controlled generator that has been selected in advance when a system accident occurs, a stability evaluation model generation unit that prepares, before an accident occurs, model definition information for estimating a future value of a phase angle deviation used to determine whether or not one or more generators included in the power system have lost synchronism, and a discrimination reference value used to determine whether or not the one or more generators have lost synchronism, based on a result of the immediately preceding transient stability calculation; a correction coefficient generating unit that prepares correction preparation information for obtaining a correction value required for estimating a future value of a phase angle deviation used to determine whether or not one or more generators included in the power system have lost synchronism before an accident occurs; an additional power control execution unit that adjusts the discrimination reference value prepared by the stability evaluation model generation unit based on the measurement values ​​of the power system after the occurrence of an accident, and selects and controls an additional power control generator when it is determined that a generator included in the power system will lose synchronism based on the measurement values ​​of the power system before and after the occurrence of the accident, the model definition information, a future value of a phase angle deviation predicted from the correction preparation information, and the adjusted discrimination reference value; A power grid stabilization system comprising:

2. The additional power control execution unit, a high-speed information collection unit that collects measurement values ​​of the power system, including at least the effective power of each generator, the phase angle difference between the interconnection point and each generator, the voltage of the interconnection point, and the effective power of the interconnection line, at a faster interval than the system information before and after the occurrence of the fault; a generator state correction unit that determines a correction value and / or a coefficient used when estimating a generator state based on the correction preparation information prepared by the correction coefficient generation unit; a generator state calculation unit that calculates or estimates a phase angle deviation of an integrated generator model in which one or more generators included in the power system are converted into one generator, based on the model definition information prepared by the stability evaluation model generation unit, the measurement values ​​for a certain period before and after the occurrence of the accident collected by the high-speed information collection unit, and the correction value and / or the coefficient obtained by the generator state correction unit; an output change estimation unit that estimates a change in an active power deviation of the integrated generator model due to parallel-off of the first electrical control generator and the additional electrical control generator; a discrimination criterion adjustment unit that adjusts the discrimination criterion value based on a phase angle difference between the interconnection point and each generator collected by the high-speed information collection unit; a stability determination unit that determines whether or not a step-out has occurred based on the phase angle deviation of the integrated generator model calculated or estimated by the generator state calculation unit and the determination reference value adjusted by the determination reference adjustment unit; an additional control generator selection unit that selects the additional control generator when the stability determination unit determines that a step-out has occurred; Equipped with The power grid stabilization system according to claim 1 .

3. the correction coefficient generation unit includes a stability limit correction ratio calculation unit that calculates a ratio required for calculating a coefficient used to estimate the active power deviation, based on the active power deviation and the phase angle deviation of the integrated generator model obtained from a result of the unstable transient stability calculation; the generator state correction unit includes a phase angle deviation second coefficient calculation unit that calculates a second coefficient for calculating the active power deviation from a sine value change amount of a phase angle, based on the ratio calculated by the stability limit correction ratio calculation unit and the active power deviation and the phase angle deviation of the integrated generator model, the generator state calculation unit calculates the phase angle deviation by changing a coefficient of a calculation formula for estimating the active power deviation to the second coefficient calculated by the phase angle deviation second coefficient calculation unit after the active power deviation increases with an increase in the phase angle deviation and reaches a maximum. The power grid stabilization system according to claim 2 .

4. the correction coefficient generation unit includes an electric torque conversion value function calculation unit that determines a coefficient of an approximation function that calculates a difference between the active power deviation and the electric torque deviation, based on a relationship between the active power deviation and the electric torque deviation calculated from a result of the transient stability calculation, the generator state correction unit includes an electric torque conversion correction value calculation unit that calculates a first correction value for converting the active power deviation into the electric torque deviation, based on a coefficient of the approximation function calculated by the electric torque conversion value function calculation unit and the active power deviation and / or the phase angle deviation of the integrated generator model, the generator state calculation unit adds the first correction value calculated by the electric torque conversion correction value calculation unit to the active power deviation when calculating the phase angle deviation from the active power deviation. The power grid stabilization system according to claim 2 or 3.

5. the correction coefficient generation unit includes an active power deviation correction value function calculation unit that calculates, based on the active power deviation obtained from a result of the transient stability calculation, a coefficient of an approximation function for determining a second correction value for reflecting a fluctuation in the active power deviation over time, The generator state correction unit is an active power deviation correction value calculation unit that calculates the second correction value for the active power deviation by using the coefficient of the approximation function calculated by the active power deviation correction value function calculation unit; a phase angle deviation re-estimation unit that recalculates an estimated value of the phase angle deviation by using the active power deviation of the integrated generator model and the second correction value calculated by the active power deviation correction value calculation unit; Equipped with a stability determination unit that determines whether or not a loss of synchronism has occurred by using the estimated value of the phase angle deviation recalculated by the phase angle deviation re-estimation unit; The power grid stabilization system according to claim 2 or 3.

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