System stabilizing device

Abstract

To execute highly accurate system stabilization control by accurately calculating the phase angle deviation of a generator.SOLUTION: In a system stabilization device 3, a phase angle deviation calculation unit 33 calculates, in time series, a phase angle deviation Δ δ (t) from an initial value of a phase angle of an equivalent generator obtained by contracting a plurality of generators on the basis of measured data ni (t) of rotation speeds of the plurality of generators. The step-out prevention unit 34 predicts the occurrence of step-out of the equivalent generator based on the fluctuation of the calculated phase angle deviation Δ δ (t), and outputs an interruption command to one or more generators among the plurality of generators when the occurrence of step-out is predicted.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a power grid stabilization device. [Background technology]

[0002] A power system stabilizer prevents the entire power system from becoming unstable due to the spread of disturbances that occur after a power system fault is cleared. Various types of power system stabilizers are already in practical use, including those that prevent loss of synchronization, those that detect out-of-step generators in order to isolate them from the system, and those that prevent an increase or decrease in system frequency due to an imbalance between supply and demand, thereby maintaining frequency.

[0003] For example, Japanese Patent Application Laid-Open Publication No. 2012-182918 (Patent Document 1) discloses a power system stabilization device for preventing loss of synchronism. Specifically, the power system stabilization device in this document predicts the occurrence of loss of synchronism based on fluctuations in the electrical phase angle of a generator. When loss of synchronism is predicted based on fluctuations from the first wave to the Nth wave (N≧3), the power system stabilization device prevents loss of synchronism by selectively shutting off the minimum number of generators required. Furthermore, when the power system stabilization device in this document determines that a weak-damping phenomenon, in which fluctuations in the generator phase angle continue for a long period of time, occurs, the power system stabilization device suppresses the weak-damping phenomenon by selectively shutting off the minimum number of generators required. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-182918 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-24374 [Patent Document 3] Japanese Patent Application Laid-Open No. 2011-50152 [Non-patent literature]

[0005] [Non-Patent Document 1] Imai et al., "Development of a predictive N-wave step-out prevention control method using only local terminal information," Electric Power Theory B, Vol. 118, No. 9, 1998 [Non-patent document 2] Yoshifumi Oura, editor, "Protective Relay System Engineering", First Edition, Institute of Electrical Engineers of Japan, March 2002, pp. 262-264 Summary of the Invention [Problem to be solved by the invention]

[0006] The grid stabilization devices described in the above-mentioned JP 2012-182918 A (Patent Document 1) and the related JP 2011-24374 A (Patent Document 2) assume that the mechanical input is constant for the first and second wave oscillations, and calculate the deviation from the initial value of the electrical phase angle by integrating the difference between the mechanical input and the electrical output based on the generator's equation of motion. Furthermore, the grid stabilization device described in JP 2012-182918 A (Patent Document 1) calculates the phase angle between the local end and the remote end using only the local end information for the Nth wave (N≧3) oscillations, assuming that the initial value of the remote end's back voltage is a constant.

[0007] As described above, conventional grid stabilizers have had to make several assumptions to calculate the generator phase angle or the phase angle deviation from the initial value, which poses the problem of poor calculation accuracy when these assumptions are violated.

[0008] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide a power system stabilization device that can perform highly accurate stabilization control by accurately calculating the phase angle of a generator or the phase angle deviation from an initial value. [Means for solving the problem]

[0009] A power system stabilization device according to one embodiment includes a rotation speed data acquisition unit, a voltage and current data acquisition unit, a phase angle deviation calculation unit, and a step-out prevention unit. The rotation speed data acquisition unit acquires, in a time series, actual measurement data of the rotation speeds of multiple generators on the power system's own end. The voltage and current data acquisition unit acquires, in a time series, detection data of the output voltages and output currents of the multiple generators. The phase angle deviation calculation unit, based on the actual measurement data of the rotation speeds of the multiple generators, time-series calculates a phase angle deviation from an initial value of the phase angle of an equivalent generator obtained by condensing the multiple generators. The step-out prevention unit predicts the occurrence of step-out of the equivalent generator based on fluctuations in the calculated phase angle deviation, and if step-out is predicted, outputs a shutdown command to one or more of the multiple generators. [Effects of the Invention]

[0010] According to the above embodiment, the phase angle deviation from the initial value of the phase angle of an equivalent generator obtained by condensing multiple generators is calculated with high accuracy based on actual measurement data of the rotation speeds of multiple generators, so it is possible to provide a power system stabilization device that can perform highly accurate stabilization control. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a diagram illustrating an application example of a power system stabilizing device according to a first embodiment. [Figure 2] FIG. 2 is a block diagram showing an example of the hardware configuration of the power system stabilization device of FIG. 1. [Figure 3] FIG. 2 is a block diagram showing an example of the functional configuration of a calculation processing unit of the power system stabilizing device. [Figure 4] FIG. 2 is a diagram showing a one-machine infinite bus system model corresponding to FIG. 1. [Figure 5] FIG. 10 is a diagram for explaining transient stability determination by the equal area method. [Figure 6] 4 is a flowchart showing the operation of the power system stabilization device related to the first and second wave response control units of the out-of-step prevention unit of FIG. 3. [Figure 7] FIG. 1 is a diagram for explaining a two-machine system model. [Figure 8]FIG. 7B is a vector diagram of the two-machine system model of FIG. [Figure 9] 4 is a flowchart showing the operation of the power system stabilization device related to the N-th wave response control unit of the out-of-step prevention unit of FIG. 3. [Figure 10] FIG. 10 is a diagram conceptually showing a fluctuation waveform of a phase angle deviation. [Figure 11] 4 is a flowchart showing the operation of a weak braking response control section in the out-of-step prevention section of FIG. 3; [Figure 12] FIG. 1 is a diagram showing a one-machine infinite bus model. [Figure 13] 13 is a vector diagram of the one-machine infinite bus model of FIG. 12. [Figure 14] 4 is a flowchart showing the operation of the out-of-step separating unit of FIG. 3; [Figure 15] FIG. 10 is a diagram illustrating an application example of a power system stabilizing device according to a fifth embodiment. [Figure 16] FIG. 11 is a block diagram showing an example of the functional configuration of a frequency abnormality prevention unit in a power system stabilizing device according to a fifth embodiment. [Figure 17] FIG. 20 is a block diagram showing an example of the functional configuration of a frequency abnormality prevention unit in a system stabilizing device according to a sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Each embodiment will be described in detail below with reference to the drawings. The same or corresponding parts will be denoted by the same reference characters and description thereof will not be repeated.

[0013] Embodiment 1 [Application example of power system stabilization device] FIG. 1 is a diagram illustrating an application example of a power system stabilization device according to a first embodiment. As an example, the power system stabilization device 3 in FIG. 1 is applied to a power system in which power is supplied to a main system from a power plant 1 having a plurality of generators GA1 to GAn via parallel transmission lines F1 and F2. When a loss of synchronism is predicted when the faulty transmission line is disconnected after a fault occurs in the power system, the power system stabilization device 3 selectively opens circuit breakers CB1 to CBn to limit the amount of power supplied from the power plant 1 to the main system. This stabilizes the power system. As will be described later, the power system stabilization device 3 also has functions such as isolating a group of generators that have lost synchronism and preventing frequency abnormalities.

[0014] The generators GA1 to GAn are, for example, pumped storage generators. The generators GA1 to GAn of the power plant 1 are connected to a common power plant bus B1 via individual generator buses BG1 to BGn and individual circuit breakers CB1 to CBn, respectively. The power plant bus B1 is connected to a substation bus B2 of the substation 2, which is an interconnection point with the main grid, via, for example, two transmission lines F1 and F2. In the first embodiment, the substation bus B2 is treated as an infinite bus.

[0015] The power system stabilization device 3 receives detection signals of the output voltages of the corresponding generators GAi (i = 1 to n) from voltage transformers VT connected to the generator buses BG1 to BGn, respectively. Furthermore, the power system stabilization device 3 receives detection signals of the output currents of the corresponding generators GAi (i = 1 to n) from current transformers CT connected to individual lines between the generators GA1 to GAn and the power plant bus B1. Furthermore, the power system stabilization device 3 receives actual measured values ​​of the rotational speed from each of the generators GA1 to GAn. In this disclosure, the rotational speed of a generator means the number of rotations per unit time (for example, rpm: revolutions per minute), and refers to the rotational speed.

[0016] [Example of hardware configuration for grid stabilization equipment] Fig. 2 is a block diagram showing an example of the hardware configuration of the power grid stabilization device 3 of Fig. 1. Fig. 2 shows an example in which the power grid stabilization device 3 is configured by a computer.

[0017] 2, the power system stabilization device 3 includes one or more input converters 10, one or more sample-and-hold (S / H) circuits 11, a multiplexer (MUX) 12, and an A / D (Analog to Digital) converter 13. The power system stabilization device 3 also includes one or more CPUs (Central Processing Units) 14, RAMs (Random Access Memory) 15, ROMs (Read Only Memory) 16, and an auxiliary storage device 17. These components form an arithmetic processing unit 21. The power system stabilization device 3 also includes one or more input / output interfaces 18 and a communication device 19. The power system stabilization device 3 also includes a bus 20 that interconnects the A / D converter 13, the arithmetic processing unit 21, the one or more input / output interfaces 18, and the communication device 19.

[0018] The input converter 10 has an auxiliary transformer (not shown) for each input channel. Each auxiliary transformer converts the detection signal from each electrical quantity detector (voltage transformer VT and current transformer CT) in Fig. 1 into a signal with a voltage level suitable for subsequent signal processing.

[0019] A sample-and-hold circuit 11 is provided for each input converter 10. The sample-and-hold circuit 11 samples and holds a signal representing an electrical quantity (voltage or current) received from the corresponding input converter 10 at a specified sampling frequency.

[0020] The multiplexer 12 sequentially selects the signals held in the plurality of sample-and-hold circuits 11. The A / D converter 13 converts the signal selected by the multiplexer 12 into a digital value. Note that by providing a plurality of A / D converters 13, A / D conversion may be performed in parallel on detection signals of a plurality of input channels.

[0021] The CPU 14 controls the entire system stabilization device 3 and executes arithmetic processing according to a program. The RAM 15 as a volatile memory and the ROM 16 as a nonvolatile memory are used as the main memory of the CPU 14. The ROM 16 stores programs, setting values ​​for signal processing, etc. The auxiliary storage device 17 is an electrically rewritable nonvolatile memory with a larger capacity than the ROM 16, and stores programs, data on detected values ​​of electricity, etc.

[0022] The input / output interface 18 is an interface circuit for exchanging digital signals between the CPU 14 and external devices. The communication device 19 performs data communication with other devices such as terminal devices.

[0023] 2, at least a part of the arithmetic processing unit 21 can be configured using circuits such as an FPGA (Field Programmable Gate Array) and / or an ASIC (Application Specific Integrated Circuit), etc. Also, at least a part of the arithmetic processing unit 21 can be configured using analog circuits.

[0024] [Example of functional configuration of power system stabilization device] 3 is a block diagram showing an example of the functional configuration of the arithmetic processing unit 21 of the power system stabilizing device 3. The power system stabilizing device 3 includes a rotation speed data acquiring unit 31, a voltage / current data acquiring unit 32, a phase angle deviation calculating unit 33, a frequency calculating unit 40, a mechanical input calculating unit 41, a step-out prevention unit 34, a step-out separation unit 38, and a frequency abnormality preventing unit 42. These functions are realized, for example, by the CPU 14 of the arithmetic processing unit 21 operating in accordance with a program.

[0025] The rotation speed data acquisition unit 31 acquires the rotor rotation speed n from each generator GAi (i=1 to n) installed in the power plant 1. i The actual measured values ​​of (t) are obtained in time series.

[0026] The voltage and current data acquisition unit 32 acquires instantaneous voltage value data v detected by the voltage transformer VT corresponding to each generator GAi. i (t) is acquired in time series, and the instantaneous value data i of the current detected by the current transformer CT corresponding to each generator GAi is i The analog data (t) is converted into digital data by the A / D converter 13.

[0027] The phase angle deviation calculation unit 33 calculates the rotation speed n of each generator GAi (i=1 to n) acquired by the rotation speed data acquisition unit 31. i By integrating the measured value of (t), the initial value δ 0,i Electrical phase angle δ from i (t) deviation Δδ i Furthermore, as will be described in detail later, the phase angle deviation calculation unit 33 calculates in time series the deviation Δδ(t) of the electrical phase angle δ(t) from the initial value δ0 of the equivalent generator GA obtained by contracting the n generators GAi. In this disclosure, the electrical phase angle δ(t) is also simply referred to as the phase angle δ(t).

[0028] The frequency calculation unit 40 calculates the rotation speed n of the rotor of each generator GAi (i=1 to n). i Based on the measured value of (t), the electrical frequency F of each generator GAi (i = 1 to n) i Furthermore, as will be described in detail later, the frequency calculation unit 40 calculates in time series the electrical frequency F(t) of the equivalent generator GA obtained by contracting the n generators GAi.

[0029] The mechanical input calculation unit 41 calculates the voltage data v of each generator GAi (i=1 to n) acquired by the voltage and current data acquisition unit 32. i (t) and current data i i (t) based on the electrical output P of the equivalent generator GA E and the rotation speed n of each generator GAi (i=1~n) i By substituting the second derivative of the electrical phase angle δ of the equivalent generator GA based on the measured value of (t) into the generator oscillation equation, the mechanical input P of the equivalent generator is Mis calculated over time. Mechanical input P M The calculation method will be described in detail later.

[0030] The step-out prevention unit 34 predicts and calculates the optimal control amount required to prevent various disturbances that occur in the power system, such as when a transmission line is cut off due to a system accident, from progressing to step-out after the disturbance occurs, and then executes the predicted control amount.

[0031] More specifically, the step-out prevention unit 34 includes a first and second wave response control unit 35 for appropriately dealing with the first and second wave of fluctuation, an Nth wave response control unit 36 ​​(N≧3) for appropriately dealing with the Nth wave (N≧3) from the third wave onwards, and a weak braking response control unit 37 for appropriately dealing with a weak braking phenomenon in which fluctuations of similar amplitude continue and do not converge. The first and second wave response control units 35 will be described in the first embodiment, the Nth wave response control unit 36 ​​will be described in the second embodiment, and the weak braking response control unit 37 will be described in the third embodiment. In this disclosure, the first and second wave response control units 35 will also be referred to as a first response control unit, the Nth wave response control unit 36 ​​will also be referred to as a second response control unit, and the weak braking response control unit 37 will also be referred to as a third response control unit.

[0032] The out-of-step isolation unit 38 isolates the out-of-step generator GAi from the power system when it detects the occurrence of out-of-step. Details of the out-of-step isolation unit 38 will be described in the fourth embodiment.

[0033] The frequency abnormality prevention unit 42 aims to maintain the frequency by implementing power supply restrictions when the frequency rises due to an excess power supply, and by implementing load restrictions when the frequency drops due to an insufficient power supply. Details of the frequency abnormality prevention unit 42 will be described in the fifth and sixth embodiments.

[0034] The feature of the system stabilization device 3 of the present disclosure is that the out-of-synchronization prevention unit 34, the out-of-synchronization separation unit 38, and the frequency abnormality prevention unit 42 all control the rotation speed n of each generator GAi (i=1 to n). iThe advantage of this method is that it performs control based on the actual measured value of (t). This allows for highly accurate system stabilization control.

[0035] [One-machine infinite bus system model] First, a description will be given of a one-machine infinite bus system model used for determining stability in the first and second wave response control unit 35 of the step-out prevention unit 34 in Fig. 3. Referring to Fig. 1, the electrical phase angle of each generator GAi (i = 1 to n) is expressed as δ i and the inertia constant is M Ai and the mechanical input is P Mi [pu], and the electrical output (effective power) is P Ei The equation of motion of the generator GAi can be expressed by the following equation (1): Note that since the following equation (1) is expressed in units (PU), the second derivative of the phase angle is divided by the reference angular frequency ω0.

[0036]

number

[0037] When focusing on power oscillations, the n generators GA1 to GAn at one end can be reduced to one equivalent generator GA, and the substation bus B2 at the other end can be treated as an infinite bus. Specifically, by adding up the above equation (1) from i=1 to i=n, ​​the equation of motion for the equivalent generator GA in the one-machine infinite bus system model can be obtained as shown in the following equation (2). Note that it is not necessary to reduce all of the n generators installed in the power plant 1; only a selected portion of the generators, such as high-output generators, can be reduced.

[0038]

number

[0039] FIG. 4 is a diagram showing a one-machine infinite bus system model corresponding to FIG. 1. In FIG. 4 and the above equation (2), the phase angle of the equivalent generator GA is δ, and the inertia constant is M A and the mechanical input is P M[pu] and the electrical output is P E +jQ E (active power P E [pu], reactive power Q E [pu]), and the back voltage is E A and the voltage of the power plant bus B1 is V A and the output current to the grid is I A The phase angle of the substation bus B2, which is an infinite bus, is fixed to 0°, and the voltage of the substation bus B2 is V B The inertia constant M of the equivalent generator GA is A , electrical phase angle δ (also simply referred to as phase angle δ), mechanical input P M , and electrical power P E is expressed as the following equations (3A) to (3D) using the values ​​of each generator GAi (i = 1 to n). That is, the phase angle δ of the equivalent generator GA is calculated by multiplying the phase angle δ of each generator GAi by the following equations (3A) to (3D). i The inertia constant M Ai The inertia constant M of the equivalent generator GA is A , mechanical input P M , and electrical power P E is the inertia constant M of each individual generator GAi (i=1~n) Ai , mechanical input P Mi , and electrical power P Ei It is expressed as the sum of the above.

[0040]

number

[0041] In this embodiment, the rotation speed n measured by each generator GAi is i (t) [rpm] is numerically integrated over time to obtain the phase angle δ i The feature of this method is that it calculates the deviation Δδ(t) from the initial value δ0 of (t). The reference frequency of the power system is F0 [Hz], the reference angular frequency is ω0 = 2πF0, the number of poles of the generator is p, and the initial phase angle at the calculation start time t0 is δ 0,i Then, the phase angle δ of the generator GAi i(t) can be expressed by the following equation (4A): In the following equation (4A), p / 2 represents the number of pole pairs, and n i / 60 represents the number of revolutions per second [rps]. Also, as shown in the following equation (4B), the initial phase angle δ 0,i The deviation from Δδ i (t). The angular frequency ω of each generator GAi i (t) is expressed by the following equation (4C).

[0042]

number

[0043] Substituting the above equation (4A) into equation (3B) gives the following equation (5A), so the phase angle δ of the equivalent generator GA in the one-machine infinite bus model can be expressed as the following equation (5B). In the following equation (5B), the initial phase angle of the equivalent generator GA at the calculation start time t0 is δ0, and the phase angle deviation of the equivalent generator GA from the initial phase angle δ0 is Δδ(t). Therefore, the phase angle deviation Δδ of the equivalent generator GA can be expressed as the phase angle deviation Δδ of the generator GAi (i = 1 to n) as shown in the following equation (5C). i The inertia constant M Ai It is expressed as a weighted average by

[0044]

number

[0045] The electrical output P of each generator GAi (i=1~n) Ei is the voltage v measured by the voltage transformer VT installed for each generator GAi. i and the current i measured by the current transformer CT installed for each generator GAi. i Therefore, as shown in the above equation (3D), the electrical output P of all the generators GAi (i = 1 to n) Ei By summing up the calculation results, the electrical output P of the equivalent generator GA in the one-machine infinite bus model is calculated. E can be obtained.

[0046] [Transient stability assessment using the equal area method] The first and second wave response control unit 35 performs transient stability determination using the so-called equal area method. Below, we will explain transient stability determination using the equal area method in the case where a ground fault occurs on transmission line F2 in the two-circuit transmission line shown in Figures 1 and 4, and then transmission line F2 is disconnected from the power grid in a short time and power is transmitted only through transmission line F1.

[0047] Fig. 5 is a diagram for explaining transient stability determination by the equal area method. Fig. 5(A) shows an example of a power phase difference angle curve in the case of no control where the generator is not shut down, and Fig. 5(B) shows an example of a power phase difference angle curve in the case where the generator is shut down. In Fig. 5(A) and Fig. 5(B), the vertical axis represents the electrical output P of the equivalent generator GA in the one-machine infinite bus model. E The horizontal axis represents the phase angle δ of the equivalent generator GA.

[0048] Referring to FIG. 5(A), in the initial operating state, the equivalent generator GA is operated at a synchronous speed with an initial phase angle δ0, and the mechanical input P M is the electrical output P E Therefore, the mechanical input power P of the equivalent generator GA at the initial operating point is M is the voltage v measured by the voltage transformer VT corresponding to the generator GAi (i=1~n). i (t) and the current measured by the current transformer CT, i i (t) can be used to calculate

[0049] When a ground fault occurs at time t = t0, the electrical output decreases but the mechanical input remains unchanged. This power difference causes the rotor speed of each generator GAi to increase, resulting in an increase in the phase angle δ over time. As already explained, the deviation Δδ(t) of the phase angle of the equivalent generator GA from the initial value δ0 is expressed as a function of the rotational speed n of each generator GAi (i = 1 to n) as shown in equation (5C). i It is calculated based on the following.

[0050] phase angle δ=δ PWhen this occurs, the faulted transmission line F2 is disconnected from the power grid. This causes the operating point (PE, δ) to move along the power phase angle curve of the single circuit. The power phase angle equation for the single circuit is the maximum value P MAX Using the above equation (5B), the following equation (6A) can be expressed as the following equation (6B):

[0051]

number

[0052] From the above equation (6B), it can be assumed that the power phase difference angle equation is expressed as a linear combination of the function sin(Δδ) and the function cos(Δδ) as shown in the following equation (7). The unknown coefficients P1 and P2 in the following equation (7) are P The following phase angle deviation Δδ and electrical output P E It can be determined by the least squares method using the measured values ​​of and .

[0053]

number

[0054] phase angle δ=δ Q When this happens, the electrical output P E is the mechanical input P M After that, the rotor of each generator GAi slows down, but the phase angle δ continues to increase. In Figure 5(A), Q P up to M -P E The integral of with respect to δ represents the acceleration energy of the rotor of the equivalent generator GA. The acceleration energy is shown by the coarsely hatched area.

[0055] phase angle δ=δ U In the figure, the estimated power phase difference angle curve of one circuit and P M = a constant line again. This intersection is an unstable equilibrium point. In Figure 5(A), δ = δ Q From δ = δ U P up to E -PM The integral of with respect to δ represents the deceleration energy of the rotor of the equivalent generator GA. The deceleration energy is shown by the area hatched with fine dots.

[0056] In this embodiment, the rotation speed n of the generator GAi (i=1 to n) i The rotational energy of the equivalent generator GA at any time t1 selected during the measurement period is expressed as the acceleration energy J A The angular frequency of the equivalent generator GA at time t1 is ω(t1), the reference angular frequency is ω0, and the inertia constant of the equivalent generator GA is M A Then, the acceleration energy J A is expressed by the following equation (8A). Furthermore, similar to equation (4A), the angular frequency ω(t1) can be expressed using the number of pole pairs p / 2 and the rotation speed n(t1) [rpm] of the equivalent generator GA at time t1. As shown in the following equation (8B), the rotation speed n(t) of the equivalent generator GA is calculated by multiplying the rotation speed n of the generator GAi (i=1 to n) by i Inertia constant M of (t) Ai It is expressed as a weighted average by

[0057]

number

[0058] The acceleration energy J in equation (8A) above A The deceleration energy J compared to D As shown in the following equation (9), the phase angle δ (t=t1) at time t1 is converted into the phase δ at the unstable equilibrium point. U Until then, P E -P M The integral calculation is performed by converting the phase angle δ into the phase angle deviation Δδ. In the following equation (9), the phase angle deviation at the unstable equilibrium point is Δδ U It is expressed as:

[0059]

number

[0060] Acceleration energy J A is the deceleration energy J D (i.e., J A >J D ), the phase angle δ is the unstable equilibrium point δ U It continues to increase beyond δ U From this point on, the phase angle δ increases without limit due to the generation of acceleration energy, and the equivalent generator GA is judged to be unstable. On the other hand, the acceleration energy J A is the deceleration energy J D (i.e., J A <J D ), the phase angle δ is the unstable equilibrium point δ U After that, the rotor repeatedly decelerates and accelerates, and finally reaches the stable equilibrium point (δ = δ Q ) and continues to operate at synchronous speed. In this case, the equivalent generator GA is judged to be stable.

[0061] Next, referring to Figure 5(B), the phase angle δ = δ Q The operation of the equivalent generator GA up to this point is the same as in the case of FIG. 5(A), so the description will not be repeated.

[0062] phase angle δ=δ SH In this case, the circuit breaker CBi corresponding to the selected generator GAi is opened. As a result, the mechanical input of the equivalent generator GA is P M From P M The amount of reduction in mechanical input is the electrical output P of the selected generators GAi at the initial operating point when these generators GAi are operating at synchronous speed. E Therefore, the voltage v measured at the voltage transformer VT corresponding to these generators GAi during synchronous operation is i (t) and the current during synchronous operation measured by the current transformer CT, i i Using (t), the reduction in mechanical input can be determined.

[0063] phase angle δ=δ U In ', the estimated power phase difference angle curve of one circuit and the mechanical input after reduction, PM This intersection is the unstable equilibrium point after some generators are shut off. In Figure 5(B), δ = δ Q From δ = δ SH P up to E -P M Integrating by δ and δ=δ SH From δ = δ U 'P E -P M The sum of ' with the integral by δ represents the deceleration energy of the rotor of the equivalent generator GA. The deceleration energy is shown by the area hatched with fine dots.

[0064] As in the case of FIG. 5(A), in this embodiment, the rotation speed n i The rotational energy of the equivalent generator GA at any time t1 selected during the measurement period is expressed as the acceleration energy J A ' is calculated as acceleration energy J A ' is the J in equation (8A) A This acceleration energy J A ' compared to the deceleration energy J D ' is the phase angle δ (t=t1) at time t1 at which some generators GAi are shut off, δ=δ SH P up to E -P M and the phase angle δ=δ SH From the phase δ at the unstable equilibrium point U 'P E -P M The integral calculation is performed by converting the phase angle δ into the phase angle deviation Δδ.

[0065]

number

[0066] As in the case of Fig. 5(A), the acceleration energy J A ' is the deceleration energy J D ' (i.e., J A '>J D'), the phase angle δ is the unstable equilibrium point δ U ' and continues to increase. δ U After that, the phase angle δ increases without limit because acceleration energy is generated, and the equivalent generator GA is judged to be unstable. On the other hand, the acceleration energy J A ' is the deceleration energy J D ' (i.e., J A ' <J D '), the phase angle δ is the unstable equilibrium point δ U ', the rotor then decelerates and accelerates repeatedly, and finally reaches the stable equilibrium point of the power phase difference angle curve of one circuit (i.e., δ = δ R ) and continues to operate at synchronous speed. In this case, the equivalent generator GA is judged to be stable.

[0067] [Operation of the first and second wave response control units in the step-out prevention unit] Fig. 6 is a flowchart showing the operation of the power system stabilizing device 3 related to the first and second wave response control unit 35 of the out-of-step prevention unit 34 in Fig. 3. The explanation so far will be summarized below with reference to Fig. 6.

[0068] In step S10 of FIG. 6, the rotation speed data acquisition unit 31 acquires the rotation speed n of each generator GAi (i=1 to n) from time t0 when the power grid fault occurs. i The voltage and current data acquisition unit 32 starts acquiring data of the voltage data v detected by the voltage transformer VT corresponding to each generator GAi. i (t), and the current data i detected by the current transformer CT corresponding to each generator GAi. i Start acquiring (t).

[0069] In practice, the rotation speed data acquisition unit 31 and the voltage / current data acquisition unit 32 constantly acquire data, and store data for a certain period up to the present time in memory by replacing the oldest data with the latest data.

[0070] In the next step S20, the phase angle deviation calculation unit 33 calculates the rotation speed n of each generator GAi (i=1 to n) acquired by the rotation speed data acquisition unit 31. i Based on the data of (t), the phase angle deviation Δδi(t) of each generator GAi is calculated in time series according to the above-mentioned equation (4B). Furthermore, the phase angle deviation calculation unit 33 calculates the phase angle deviation Δδ(t) of the equivalent generator GA in time series according to equation (3B).

[0071] The first and second wave response control unit 35 also calculates the voltage data v acquired by the voltage and current data acquisition unit 32. i (t) and current data i i Based on (t), the electrical output P of each generator GAi Ei Furthermore, the first and second wave response control unit 35 calculates the electrical output P of n generators GAi (i=1 to n) as shown in equation (3D). Ei By adding (t), the electrical output P of the equivalent generator GA E (t) is calculated over time.

[0072] In the next step S30, the first and second wave response control unit 35 compares the time series data of the phase angle deviation Δδ(t) of the equivalent generator GA obtained after the fault system is cut off with the time series data of the electrical output P E Based on the time series data (t) and (t), the power phase difference angle curve after the faulted system is shut off is estimated. Specifically, as explained with reference to the above equation (7), the power phase difference angle equation is determined by using the least squares method.

[0073] In the next step S40, the first and second wave response control unit 35 calculates the power phase difference angle curve estimated after the fault system is removed from the initial phase angle θ0 at the time of the fault occurrence, and calculates the power phase difference angle curve estimated after the fault system is removed from the initial mechanical input P M The phase angle δ when Q Up to mechanical input P M and electrical output P E Difference P M -P E By integrating, the acceleration energy J AFurthermore, the first and second wave corresponding control unit 35 calculates the above phase angle δ Q From the above, the estimated power phase difference angle curve after the fault system is removed is the same as the initial mechanical input P M The phase angle δ when it coincides with U (i.e., unstable equilibrium point), the electrical output P E and mechanical input P M Difference P E -P M By integrating, the deceleration energy J D Calculate.

[0074] In the next step S50, the first and second wave response control unit 35 calculates the acceleration energy J A is the deceleration energy J D Determine whether the acceleration energy J is smaller than A is the deceleration energy J D If the acceleration energy J is smaller than the predetermined value (YES in step S50), the first and second wave response control unit 35 determines that the power system is stable and ends the process. A is the deceleration energy J D In the above cases (NO in step S50), the first and second wave response control unit 35 determines that the power grid is unstable, and proceeds to step S60.

[0075] In step S60, the first and second wave response control unit 35 selects a generator to be shut off. Here, the angular frequency ω of the generator GAi (i=1 to n) expressed by the above-mentioned formula (4C) is i A generator having a large deviation between (t) and the reference angular frequency ω0 may be selected as the object to be controlled.

[0076] In the next step S70, the first and second wave response control unit 35 calculates the acceleration energy J A ' and deceleration energy J D ' is calculated. In this case, the acceleration energy J A ' is the acceleration energy J calculated in step S40 A Equal to the deceleration energy J D' is the value that the estimated power phase difference angle curve after the fault system is removed is the same as the initial mechanical input P M The phase angle δ when Q Phase angle δ when the generator is disconnected from SH Up to the electrical output P E and the initial mechanical input P M Difference P E -P M The integrated value and the above phase angle δ SH From the above, the estimated power phase difference angle curve is M The phase angle δ when it coincides with ' U ', electrical output P E and the mechanical input P after the generator is shut off M ' and the difference P E -P M ' is equal to the sum of the integrated values.

[0077] In the next step S80, the first and second wave response control unit 35 calculates the acceleration energy J A ' is the deceleration energy J D Determine whether the acceleration energy J is smaller than '. A ' is the deceleration energy J D If it is smaller than ' (YES in step S80), the first and second wave response control unit 35 determines that the power system is stable and proceeds to step S90. In step S90, the first and second wave response control unit 35 outputs a shutdown command to the generator GAi selected in step S60 and ends the process.

[0078] On the other hand, the acceleration energy J A ' is the deceleration energy J D In the above cases (NO in step S80), the first and second wave response control unit 35 determines that the power system is unstable and returns the process to step S60. In step S60, the first and second wave response control unit 35 selects an additional generator to be shut off. The subsequent process from step S70 onwards is similar, so the description will not be repeated.

[0079] [Effects of the First Embodiment] As described above, the phase angle deviation calculation unit 33 of the power system stabilization device 3 calculates the rotation speed n of each generator GAi (i=1 to n). i Based on the measured data, the phase angle deviation Δδ(t) of the equivalent generator GA is calculated with high precision. By using this highly accurate phase angle deviation Δδ(t), the first and second wave response control unit 35 of the step-out prevention unit 34 can perform highly accurate shutdown control of the generator to prevent step-out in advance due to the first and second wave oscillations.

[0080] Embodiment 2 [Outline of the Nth wave response control unit in the step-out prevention unit] In the second embodiment, the operation of the N-wave response control unit 36 ​​of the step-out prevention unit 34 in the power system stabilization device 3 of Fig. 3 will be described. In the case of N-wave (N≧3) oscillations, the substation bus B2 cannot be treated as an infinite bus with a phase angle of 0°. Furthermore, because it is necessary to take governor control into consideration, it is inappropriate to assume that the mechanical input at the local end is constant. Therefore, the power system is simulated as a two-machine power system model in which an equivalent generator at the local end and an equivalent generator at the other end are connected via a transmission line.

[0081] The following explanation is basically based on "Development of a predictive N-wave step-out prevention control method using only local terminal information," Electric Power Theory B, Vol. 118, No. 9, 1998 (Non-Patent Document 1). However, in the second embodiment, as in the first embodiment, the rotation speed n of each generator GAi (i = 1 to n) is i This differs from the control method in the same document in that the phase angle deviation Δδ(t) based on the actual measurement data is used.

[0082] [Two-machine system model] FIG. 7 is a diagram for explaining a two-machine system model. As shown in FIG. 7(A), the main system corresponding to the self-end generator GAi (i=1 to n) becomes a multi-machine system 4 including a large number of generators and a transmission line network in an actual system. However, when focusing on the power oscillation mode to be considered as a stabilization target, the main system side other than the self-end is as if it were a single equivalent generator GB and a transmission line (line reactance X L) That is, the entire power system can be simulated as a two-machine system model as shown in Figure 7(B).

[0083] In Figure 7(B), the equivalent generator GA at its own end has a back voltage E A (also called internal voltage), phase angle δ A , internal reactance X A , inertia constant M A , damping coefficient D A , mechanical input P MA , electrical output P EA The equivalent generator GB at the other end has a back voltage E B , phase angle δ B , inertia constant M B , damping coefficient D B , mechanical input P MB , electrical output P EB The voltage at the measurement point (i.e., the power plant bus B1 in Figure 1) is V A Let the line reactance between the self-end and the other end be X L The current output from the terminal to the transmission line is I A and the current output from the other end to the transmission line is I B The phase angle δ of the equivalent generator GA at the self-end A and the phase angle δ of the equivalent generator GB at the other end B The phase difference between A -δ B is.

[0084] Of the above, the back voltage E of the equivalent generator GB at the other end B , inertia constant M B , damping coefficient D B , mechanical input P MB and the line reactance X L are unknown quantities. In the second embodiment, these unknown quantities are determined based on the measured values ​​on the local side. As in the first embodiment, the phase angle deviation Δδ of the phase angle δ between the local side and the other side is determined by the rotation speed n of each generator GAi on the local side. i It can be calculated from the detected value of (t).

[0085] In the case of the first embodiment, that is, in the case of the first and second oscillation waves, the back voltage E of the equivalent generator GB at the other end B In the case of the second embodiment, that is, in the case of the Nth oscillation wave (N≧3), the back voltage E of the equivalent generator GB at the other end B The initial value of is given as a constant, and the self-terminal voltage V A and the self-terminal current I A Using the measured value of L Calculate the back voltage E B The initial value of is corrected. This will be specifically described below with reference to the drawings.

[0086] [Calculating line reactance] Figure 8 is a vector diagram of the two-machine system model in Figure 7(B). In Figure 8, the self-terminal current I A and the self-terminal voltage V A The phase angle between the two is α, and the back voltage E B and the self-terminal voltage V A The phase angle between is β.

[0087] Referring to FIG. 7(B) and FIG. 8, the effective power P output from the equivalent generator GA at the own end is E and reactive power Q E is expressed by the following equations (11A) and (11B).

[0088]

number

[0089] From the above equations (11A) and (11B), the phase angle α and the self-terminal current I A are expressed by the following equations (12A) and (12B).

[0090]

number

[0091] In the transient region, the back voltage E of the other end BAssuming that is a constant, the phase angle β is expressed as in the following equation (13).

[0092]

number

[0093] Here, at the point when the phase angle β is maximum, the back voltage E B Therefore, the influence of the line reactance X L is calculated by the following equation (14) at the timing when the phase angle β is maximum in each oscillation wave (i.e., the timing when the phase angle deviation Δδ is maximum).

[0094]

number

[0095] In the above equation (14), the line reactance X L After calculating (i.e., after the acceleration of the first wave of oscillation has finished), this line reactance X L The phase angle β is calculated using the following equation (15).

[0096]

number

[0097] After that, from the second wave of the oscillation onwards, the back voltage E of the other end is adjusted so that the difference between the phase angle β calculated using the above formula (13) and the phase angle β calculated using the above formula (15) becomes smaller. B and line reactance X L This correction corrects the value of the back voltage E B Appropriate back voltage E that is not affected by the initial value of B and line reactance X L The value of can be obtained.

[0098] [Calculating the generator constants at the other end] Inertia constant M of the equivalent generator GB at the other end Band damping coefficient D B The generator constants such as the above can be calculated with high accuracy by applying the time series data of the phase angle deviation Δδ(t) explained in the first embodiment to the equation of motion of the equivalent generator GB at the other end and applying the least squares method. Specifically, the equation of motion of the equivalent generator GB at the other end is calculated by applying the inertia constant M B , damping coefficient D B , reference angular frequency ω0, mechanical input P MB [pu], electrical power P EB It can be expressed by the following equation (16) using [pu]. Note that in the Nth oscillation wave (N≧3), the damping coefficient D B The following section is included.

[0099]

number

[0100] In the above equation (16), the inertia constant M B , damping coefficient D B , and mechanical input P MB is the unknown. The electrical output P EB is the electrical output P of the terminal EA The voltage data v corresponding to each generator GAi (i = 1 to n) at the own end is equal to the sign of i and current data i i The first and second derivatives of the phase angle δ can be calculated from the rotation speed n of each generator GAi explained in the first embodiment. i are equal to the first and second derivatives of the phase angle deviation Δδ based on the measured value of . Here, the electrical output P of the equivalent generator GA at its own end from time t1 to time t2 is E If time-series online data of the phase angle deviation Δδ and the phase angle deviation Δδ are obtained, then by substituting these data into the above equation (16), the determinants of the following equations (17A) to (17D) can be obtained.

[0101]

number

[0102] By solving the above equation (17A) by the least squares method, the unknown vector x expressed by equation (17D) can be calculated as shown in the following equation (18).

[0103]

number

[0104] [Oscillation prediction calculation and stability judgment] When performing oscillation prediction calculations, the two-machine system model shown in Figure 7(B) is converted into a stable equivalent one-machine infinite bus model. The inertia constant M, damping coefficient D, and electrical output P of the equivalent generator of this one-machine infinite bus model are E , and mechanical input P M is the inertia constant M of the two-machine system model A ,M B , damping coefficient D A ,D B , electrical output P EA ,P EB , and mechanical input P MA ,P MB Using these, it is expressed as the following equations (19A) to (19D).

[0105]

number

[0106] The oscillation phenomenon can be predicted by simultaneously solving the equation of motion of the following equation (20A) using the above equations (19A) to (19D) and the power phase difference angle equation of the following equation (20B) online.

[0107]

number

[0108] Using the predicted calculation results of the oscillation phenomenon, the electrical output value P of the equivalent generator increases as the phase angle δ increases. E is the mechanical input P MWhen the value of the equivalent generator GAi falls below this value, that is, when the unstable equilibrium point is exceeded, it can be determined that the equivalent generator will step out. Therefore, when it is predicted that the equivalent generator will step out, the number of generators GAi that are interrupted on the local end side can be increased one by one, and the prediction calculation can be repeated while correcting the local end model, thereby calculating the number of generators that need to be interrupted to prevent step-out.

[0109] [Operation of the Nth wave response control unit in the step-out prevention unit] Fig. 9 is a flowchart showing the operation of the power system stabilizing device 3 related to the N-wave response control unit 36 ​​of the out-of-step prevention unit 34 in Fig. 3. The description of the second embodiment up to this point will be summarized below with reference to Fig. 9.

[0110] In step S100 of FIG. 9, the Nth wave response control unit 36 ​​determines the unknown quantities of the two-machine system model in real time based on the online data of its own end after a fault occurs in the power system. In this disclosure, this step is referred to as real-time modeling. Here, the generator constants (inertia constant M B , damping coefficient D B ), mechanical input P MB , and the back voltage E B and the line reactance X between the self-end and the other end L The deviation Δδ from the initial value δ0 of the phase angle between the self-end and the other end is determined by the rotation speed n of each generator GAi (i = 1 to n) at the self-end. i It can be calculated based on the actual measured value.

[0111] Specifically, first, the N-th wave response control unit 36 ​​detects the back voltage E B Since the variation range of is relatively small, the initial value of this value is assumed to be a constant. Then, the Nth wave response control unit 36 ​​calculates the line reactance X between the own end and the other end in accordance with the above-mentioned equations (13) and (14) using the online data of the own end at the time when the phase angle deviation Δδ is maximum. L The N-th wave response control unit 36 ​​calculates the back voltage E B and line reactance X L The value of is corrected to a more appropriate value using subsequent online data.

[0112] Furthermore, the N-th wave response control unit 36 ​​applies the time series data of the phase angle deviation Δδ between the own end and the other end and the time series data P of the electrical output to the equation of motion of the equivalent generator GB at the other end. EB (=-P EA ) by substituting the generator constants (inertia constant M B , damping coefficient D B ) and mechanical input P MB Determine.

[0113] Furthermore, the N-th wave response control unit 36 ​​calculates the inertia constant M, damping coefficient D, and electrical output P of the equivalent generator in a one-machine infinite bus model that is equivalent in stability to the two-machine system model. E , and mechanical input P M Determine.

[0114] In the next step S110, the Nth wave response control unit 36 ​​determines whether the fluctuation has converged. This convergence determination is made, for example, by comparing the amplitude of a state quantity such as the phase angle δ or the phase angle deviation Δδ with a threshold value. If the fluctuation has converged (YES in step S110), the Nth wave response control unit 36 ​​ends the process, and if the fluctuation of the phase angle deviation Δδ is tending to diverge (NO in step S110), the Nth wave response control unit 36 ​​proceeds to step S120.

[0115] In step S120, the N-th wave response control unit 36 ​​numerically solves the finally obtained equation of motion (equation (20A)) of the one-machine infinite bus model and the power phase difference angle equation (equation (20B)) in combination to obtain the phase angle δ and the electrical output P E The time evolution of the vibration is calculated, and the vibration is predicted.

[0116] In the next step S130, the Nth wave response control unit 36 ​​performs stability determination based on the prediction calculation result of step S120. For example, the Nth wave response control unit 36 ​​determines whether the electrical output P E is the mechanical input P MIt can be determined that the equivalent generator will step out when the voltage drops below , that is, when the unstable equilibrium point is exceeded.

[0117] If the prediction result indicates the occurrence of a step-out as a result of the stability determination in step S130 (YES in step S140), the Nth wave response control unit 36 ​​proceeds to step S150. In step S150, the Nth wave response control unit 36 ​​determines the number of generators GAi to be interrupted on the local end side, correcting the local end model while successively increasing the number of generators GAi to be interrupted, and thereby determines the number of generators to be interrupted necessary to prevent a step-out from occurring. Thereafter, the process returns to step S100.

[0118] On the other hand, if the prediction result does not indicate the occurrence of step-out as a result of the stability determination in step S130 (NO in step S140), the N-th wave response control unit 36 ​​returns the process to step S100.

[0119] [Effects of the second embodiment] As described above, the phase angle deviation calculation unit 33 of the power system stabilization device 3 calculates the rotation speed n of each generator GAi (i=1 to n). i Based on the measured data, the phase angle deviation Δδ(t) of the equivalent generator GA is calculated with high precision. By using this highly accurate phase angle deviation Δδ(t), the Nth wave response control unit 36 ​​of the step-out prevention unit 34 can perform highly accurate shutdown control of the generator to prevent step-out in response to the Nth wave (N≧3) oscillation.

[0120] Embodiment 3 [Outline of weak braking control unit] 3, the weak braking response control unit 37 detects a phenomenon in which the amplitude of a state quantity of interest does not continue to converge to the same level (referred to as a sustained oscillation phenomenon or a weak braking phenomenon), and when this weak braking phenomenon is detected, suppresses the weak braking phenomenon by selectively cutting off the minimum necessary generator GAi at its own end. The weak braking response control is executed in parallel with the N-th wave response control described in the second embodiment.

[0121] As a conventional technique, for example, in paragraph

[0059] of Japanese Patent Laid-Open No. 2012-182918 (Patent Document 1), it is described that a simple method is E This paper describes a method for observing the fluctuation waveform by focusing on the state quantity as a parameter. However, this method has the problem that as the stability limit (i.e., the boundary between stability and instability just before an unstable state such as step-out occurs) is approached, the nonlinearity of the fluctuation waveform becomes stronger and the fluctuation waveform deviates from a trigonometric function shape, making it difficult to properly grasp the state.

[0122] Also, in paragraph

[0060] of the same document, the governor control is ignored and the mechanical input P M is constant, and the mechanical input P M is the electrical output P E The initial value P E0 is equal to P E0 -P E A method is disclosed in which a value corresponding to the electrical phase angle δ is calculated by integrating twice. In this case, a reset filter (transfer function: s / (s+ω)) is further applied to the integrated value. R )) is applied to remove the DC component and the long-period component, thereby reducing the deviation in the detected value of the phase angle δ caused by ignoring the governor control.

[0123] In the system stabilization device 3 of the present disclosure, the weak braking control unit 37 focuses on the phase angle deviation Δδ(t) of the equivalent generator GA on its own end side, explained in equations (4B) and (5C) in the first embodiment, as a state quantity, and observes its fluctuation waveform. i The phase angle deviation Δδ(t) based on (t) varies significantly depending on the characteristics and operating state of the generator, so power oscillation can be monitored more appropriately.

[0124] [Details of the operation of the weak braking control unit] 10 is a diagram conceptually showing the fluctuation waveform of the phase angle deviation Δδ.. FIG. 11 is a flowchart showing the operation of the weak braking response control section 37 in the step-out prevention section 34 of FIG.

[0125] 10 and 11, in step S200, the phase angle deviation calculation unit 33 calculates the phase angle deviation Δδ(t) of the equivalent generator GA in time series based on the detected value ni(t) of the rotation speed of each generator GAi (i = 1 to n). As a result, a time-axis waveform representing the fluctuation state of the phase angle deviation Δδ(t) is detected.

[0126] In the next step S210, the weak braking response control unit 37 determines whether the time axis waveform of the phase angle deviation Δδ indicates a bottom. If the time axis waveform of the phase angle deviation Δδ indicates a bottom (YES in step S210), the weak braking response control unit 37 calculates the bottom value (step S220).

[0127] In the next step S230, the weak braking control section 37 determines whether or not the time-axis waveform of the phase angle deviation Δδ indicates a peak. If the time-axis waveform of the phase angle deviation Δδ indicates a peak (YES in step S230), the weak braking control section 37 calculates the peak value and the oscillation amplitude A n (nth wave) is calculated (step S240).

[0128] Here, the oscillation amplitude is the value obtained by subtracting the trough value from the peak value, and the midpoint between the time when the trough value is given and the time when the peak value is given is defined as the time corresponding to the oscillation amplitude. In Figure 10 shown as an example, the oscillation amplitude A1 of the first wave is obtained at time t1, the oscillation amplitude A2 of the second wave is obtained at time t2, the oscillation amplitude A3 of the third wave is obtained at time t3, and the oscillation amplitude A4 of the fourth wave is obtained at time t4.

[0129] The amplitude of the third wave or more A n If (n≧3) is calculated (YES in step S250), the weak braking control unit 37 calculates the n-th wave damping coefficient α n In the following equation (21), the time t n The amplitude of the nth wave is A n is obtained, and at time t n-1 The amplitude of the n-1 wave is A n-1is obtained, the damping coefficient α, which indicates the degree of temporal change in the oscillation amplitude between the n-1th wave and the nth wave, n An example of the calculation formula is shown below.

[0130]

number

[0131] In the next step S270, the weak braking control section 37 calculates the braking coefficient α n The threshold α is set as SET Then, the weak braking corresponding control section 37 compares the braking coefficient α n is the threshold α SET If the braking coefficient α is greater than α (YES in step S270), the process proceeds to step S280. In step S280, the weak braking control unit 37 selects a generator to be shut off and outputs a command to shut off the circuit breaker corresponding to the selected generator. On the other hand, the weak braking control unit 37 n is the threshold α SET In the following cases (YES in step S270), the process returns to step S210.

[0132] In the above step S270, the weak braking control section 37 continuously changes the braking coefficient α n is the threshold α SET If the difference exceeds the threshold, the process may proceed to step S280.

[0133] [Effects of the Third Embodiment] As described above, the phase angle deviation calculation unit 33 of the power system stabilization device 3 calculates the rotation speed n of each generator GAi (i=1 to n). i The phase angle deviation Δδ(t) of the equivalent generator GA is calculated with high accuracy based on the measured data. The weak braking response control unit 37 of the step-out prevention unit 34 determines whether to shut down the generator based on a damping coefficient that indicates the time change in the oscillation amplitude of this highly accurate phase angle deviation Δδ(t), so that the shutdown control of the generator can be performed with high accuracy.

[0134] Embodiment 4 [Outline of the step-out separation unit] The out-of-step isolation unit 38 in FIG. 3 aims to ensure stable operation of the power system by quickly isolating the out-of-step generator group from the other generator groups when an out-of-step occurs in the power system.

[0135] Conventionally, the impedance locus method has often been adopted as a method for detecting out-of-step (for example, "Protective Relay System Engineering," edited by Yoshifumi Oura, First Edition, Institute of Electrical Engineers of Japan, March 2002, pp. 262-264 (Non-Patent Document 2)). In an out-of-step phenomenon, the impedance seen by the distance relay moves continuously within the RX plane as the phase angle δ increases. Therefore, in the impedance locus method, an out-of-step phenomenon is determined by detecting that the impedance has passed through a specified region within the RX plane after a certain threshold time.

[0136] The problem with the impedance locus method is that the operator must perform a large number of simulations to determine the threshold time for determining out-of-step, which places a burden on the operator. On the other hand, the out-of-step separation unit 38 of this embodiment determines the rotation speed n of each generator GAi (i = 1 to n). i The phase angle deviation Δδ(t) based on (t) is used to determine the electrical phase angle δ(t) of the equivalent generator. SET The threshold can be intuitively determined, for example, to 180°, thereby reducing the burden on the operator.

[0137] [Details of operation of step-out separation unit] FIG. 12 is a diagram showing a one-machine infinite bus model. In FIG. 12, the internal voltage of the equivalent generator GA at its own end is expressed as E A The phase angle is δ and the internal reactance is X A The voltage of the power plant bus B1, which is the measurement point on the local side, is V A The effective power output from the terminal is P E and the reactive power is Q E and the current is I A Let the line reactance of the transmission line connecting the equivalent generator GA at the local end and the infinite bus B2 at the other end be X L Let the voltage of the infinite bus B2 be VB and the phase angle is set to 0°.

[0138] FIG. 13 is a vector diagram of the one-machine infinite bus model of FIG. 12. FIG. 13(A) shows a vector diagram of the initial state at time t=t0, and FIG. 13(B) shows a vector diagram at time t (>t0). In FIG. 13(A), the self-terminal voltage V A and the self-terminal current I A The phase difference between the two is α, and the internal voltage E of the equivalent generator GA is A and the voltage V of the infinite bus B2 B The phase difference δ0 corresponds to the initial phase angle δ0 at the initial operating point in FIG. 5 of the first embodiment. Also, with reference to FIG. 13(B), the phase angle deviation Δδ expressed by the equations (4B) and (5C) described in the first embodiment is A (t) phase angle δ(t) and internal voltage E A This corresponds to the phase difference with the initial phase angle δ0.

[0139] Referring to Figure 13(A), the effective power P E and reactive power Q E is the self-terminal voltage V A , self-end current I A , and the phase angle α, are expressed by the following equations (22A) and (22B), respectively.

[0140]

number

[0141] In Figure 13(A), the internal voltage E A By focusing on the right triangle with the hypotenuse, the internal voltage E A is the self-terminal voltage V A , self-end current I A , internal reactance X A , and reactive power Q E Using this, it is expressed as the following equation (23A). Also, the voltage V of the infinite bus B By focusing on the right triangle with the hypotenuse, the infinite bus voltage V B is the self-terminal voltage V A, self-end current I A , line reactance X L , and reactive power Q E is expressed by the following equation (23B) using

[0142]

number

[0143] Furthermore, in Figure 13, the active power P E is the internal voltage E A , infinite bus voltage V B , initial phase angle δ0, internal reactance X A , and the line reactance X L The following equation (24A) is expressed using the voltage V of the infinite bus. B A right triangle with the hypotenuse (X A +X L )I A It can also be derived by using the analogy of a right triangle with the hypotenuse at . By solving the following equation (24A) with δ0, the internal voltage E A and infinite bus voltage V B The phase difference δ0 (i.e., initial phase angle δ0) is expressed by the following equation (24B): Furthermore, by adding the phase angle deviation Δδ(t) of equation (5C) to the phase difference δ0, the phase angle δ(t) of the equivalent generator GA is expressed by the following equation (24C):

[0144]

number

[0145] In the expression of the phase difference δ0 in the above equation (24B), the internal voltage E A is expressed by the above equation (23A), and the infinite bus voltage V B is expressed by the above equation (23B), it can be seen that the phase difference δ0 and the phase angle δ(t) can be calculated using the measured values ​​and known values.

[0146] Fig. 14 is a flowchart showing the operation of the out-of-step separating unit 38 in Fig. 3. Referring to Fig. 14, in step S300, the out-of-step separating unit 38 separates the internal voltage E A is calculated according to the above equation (23A), and the voltage V of the infinite bus is B In addition, the out-of-step separating unit 38 calculates the calculated internal voltage E A and infinite bus voltage V B Using this, the infinite bus voltage V B and the internal voltage E of the equivalent generator GA A The phase difference δ0 (that is, the initial phase angle δ0) between the two is calculated according to the above-mentioned equation (24B).

[0147] In the next step S310, the phase angle deviation calculation unit 33 in FIG. 3 calculates the actual rotation speed n i The phase angle deviation Δδ(t) of the equivalent generator GA is calculated using

[0148] In the next step S320, the out-of-step separating unit 38 calculates the phase angle δ(t) at time t by adding the phase angle deviation Δδ(t) calculated in step S310 to the phase difference δ0 calculated in step S300.

[0149] In the next step S330, the out-of-step separating unit 38 calculates the phase angle δ(t) calculated in step S320 by the threshold value δ SET As a result, the phase angle δ(t) is compared with the threshold δ SET If the phase angle δ(t) is greater than the threshold δ (step S330), the out-of-step separation unit 38 determines that the out-of-step state has occurred, and outputs a shutoff command to the out-of-step generator (step S340). SET In the following cases (YES in step S330), the process returns to step S310.

[0150] [Effects of the Fourth Embodiment] As described above, the phase angle deviation calculation unit 33 of the power system stabilization device 3 calculates the rotation speed n of each generator GAi (i=1 to n). iBased on the measured data, the phase angle deviation Δδ(t) of the equivalent generator GA is calculated with high accuracy. The step-out separation unit 38 calculates the phase angle δ(t) by adding the initial value δ0 of the phase angle to this highly accurate phase angle deviation Δδ(t), and compares the calculated phase angle δ(t) with the threshold value δ SET By comparing the phase angle δ with the threshold value δ, the occurrence of step-out can be determined with high accuracy. SET The threshold can be intuitively determined, for example, to 180°, thereby reducing the burden on the operator.

[0151] Embodiment 5 [Overview of frequency anomaly prevention unit] In the system stabilization device 3 of FIG. 3, the frequency abnormality prevention unit 42 detects a frequency abnormality phenomenon caused by a large imbalance in supply and demand of active power, and attempts to maintain the frequency by implementing power supply restrictions when the frequency rises above an upper threshold due to an oversupply, and by implementing load restrictions when the frequency drops below a lower threshold due to a supply shortage.

[0152] A conventional power grid stabilization device described in Japanese Patent Laid-Open No. 2011-50152 (Patent Document 3) includes a means for detecting a continuous decrease in the active power output of a generator and a means for detecting a continuous decrease in the system frequency based on the bus voltage. The power grid stabilization device in this document implements load shed when both the active power output of the generator and the system frequency continuously decrease.

[0153] The reduction in the generator's active power output is implemented to detect power outages due to plant failures and malfunctions. When a generator squeezes out its output in the event of a plant abnormality, it is assumed that the behavior of the generator's electrical output and its mechanical input are nearly identical.

[0154] The problems with the above-mentioned conventional technology are as follows. First, when multiple generators trip with a time lag, the behavior of the electrical output and the behavior of the mechanical input of the generators may not be the same when the second or subsequent generators trip. Therefore, there is a problem in that the electrical output of the generators cannot be used to detect the tripping of the second or subsequent generators.

[0155] Second, if there are many generators in the target system and their rotation speeds vary, the frequency calculation results will differ depending on the bus voltage measurement point, resulting in a decrease in the accuracy of frequency anomaly detection.

[0156] In the system stabilization device 55 of the fifth embodiment and the following sixth embodiment, the frequency calculation unit 40 calculates the actual rotation speed n of each generator GAi (i=1 to n) to be measured. i The mechanical input calculation unit 41 calculates the electrical frequency F(t) of the equivalent generator based on the measured values ​​of the voltage and current at its own terminal. E and the measured rotation speed n of each generator GAi (i = 1 to n) i The mechanical input P of the equivalent generator is calculated by substituting the second derivative of the phase angle δ(t) based on M The frequency abnormality prevention unit 42 calculates the calculated electrical frequency F(t) and the mechanical input P M As a result, highly accurate control for preventing frequency abnormalities can be performed. This will be described in detail below with reference to the drawings.

[0157] [Application example of power system stabilization device] Fig. 15 is a diagram showing an application example of a power system stabilization device according to embodiment 5. A power system stabilization device 55 in Fig. 15 is applied to a power system that supplies power from a power plant 51 having a plurality of generators GA1 to GAn via a transmission line 52 to a main power system 53 having a plurality of loads L1 to Ln.

[0158] As shown in Fig. 15, each of the generators GA1 to GAn is connected to a bus BA via a corresponding transformer and a corresponding circuit breaker. Specifically, the generator GA1 is connected to the bus BA via a transformer MTr1 and a circuit breaker CB1. The generator GAn is connected to the bus BA via a transformer MTrn and a circuit breaker CBn. The bus BA is connected to a main system 53 via a transmission line 52.

[0159] A current transformer that measures current is provided at the sending end of the transformer corresponding to each of the generators GA1 to GAn. Specifically, a current transformer CT1 that measures the output current of the generator GA1 is provided at the sending end of the transformer MTr1 corresponding to the generator GA1. A current transformer CTn that measures the output current of the generator GAn is provided at the sending end of the transformer MTrn corresponding to the generator GAn. In addition, a voltage transformer VT that measures the bus voltage is provided at the bus BA.

[0160] The plant control devices GA1C to GAnC are provided to correspond to the generators GA1 to GAn, respectively, and control the output of the corresponding generator when the power system is healthy. Specifically, each of the plant control devices GA1C to GAnC increases the output of the corresponding generator when the system frequency drops, and decreases the output of the corresponding generator when the system frequency rises.

[0161] The power system stabilization system 50 of FIG. 15 includes, in addition to the power system stabilization device 55, a fault detection terminal device 54 and a plurality of load control terminal devices 56_1 to 56_n corresponding to the loads L1 to Ln, respectively.

[0162] The fault detection terminal device 54 receives as input the current signals output from the current transformers CT1 to CTn, the voltage signals output from the voltage transformer VT, and signals indicating the open / closed states of the circuit breakers CB1 to CBn. Furthermore, the fault detection terminal device 54 receives as input the actual measured values ​​of the rotation speed from each of the generators GA1 to GAn. The fault detection terminal device 54 converts these analog signals into digital data and transmits them to the power system stabilization device 55. Furthermore, the fault detection terminal device 54 outputs tripping commands to each of the circuit breakers CB1 to CBn in accordance with a command from the power system stabilization device 55.

[0163] Each of the load control terminal devices 56 detects the load amount of the corresponding load and transmits data on the detected load amount to the power system stabilization device 55. In addition, the load control terminal device 56 outputs a disconnection command to the corresponding circuit breaker in accordance with a command from the power system stabilization device 55 in order to disconnect the corresponding load from the main power system 53.

[0164] The hardware configuration of each of the fault detection terminal device 54 and the load control terminal device 56 is the same as that of the power system stabilization device 3 shown in FIG.

[0165] The hardware configuration of the power system stabilization device 55 is obtained by removing the input converter 10 for detecting analog signals, the sample-and-hold circuit 11, the multiplexer 12, the A / D converter 13, and the input / output interface 18 from the hardware configuration of the power system stabilization device 3 shown in Fig. 2. In the fifth embodiment, the functions of these components are realized by a fault detection terminal device 54 and a load control terminal device 56. The functional configuration of the power system stabilization device 55 is similar to the functional configuration of the power system stabilization device 3 shown in Fig. 3.

[0166] [Details of frequency anomaly prevention unit operation] Fig. 16 is a block diagram showing an example of the functional configuration of the frequency abnormality prevention unit 42 in the system stabilization device 55 of the fifth embodiment. Fig. 16 also shows the rotation speed data acquisition unit 31, the voltage / current data acquisition unit 32, the frequency calculation unit 40, and the mechanical input calculation unit 41 of Fig. 3. The operations of the frequency calculation unit 40 and the mechanical input calculation unit 41 are the same as those in the sixth embodiment.

[0167] Referring to FIG. 16, the frequency calculation unit 40 calculates the number of rotations n of the rotor of each generator GAi (i=1 to n). i (t)[ rpm ], the electrical frequency F of each generator GAi (i = 1 to n) i (t) is calculated over time.

[0168] Specifically, if the reference frequency of the power system is F0 [Hz] and the number of poles of the generator is p, the electrical frequency F of the generator GAi expressed in units is i (t) is expressed by the following equation (25A): In the following equation (25A), p / 2 represents the number of pole pairs, and n i / 60 represents the number of revolutions per second [rps]. As shown in the following equation (25B), the frequency calculation unit 40 calculates the average value F(t) of the electrical frequencies of the set G of generators to be averaged by multiplying the inertia constant M of each target generator GAi byAi by frequency F i Calculated by weighted average of (t).

[0169]

number

[0170] As shown in the following equation (26A), the average value n(t) of the rotation speed of the generator set G is also calculated by the inertia constant M Ai Rotation speed n i Therefore, if we rewrite equation (25A) using the average value for the generator set G, we obtain the following equation (26B).

[0171]

number

[0172] The mechanical input calculation unit 41 calculates the voltage data v of each generator GAi (i=1 to n) acquired by the voltage and current data acquisition unit 32. i (t) and current data i i The electrical output P of each generator GAi based on (t) Ei Furthermore, the mechanical input calculation unit 41 calculates the electrical outputs P Ei By adding up the equivalent generator electrical power P E Calculate.

[0173] Here, by numerically differentiating both sides of the above equation (26B) with respect to time, the second-order differential of the electrical phase angle δ(t) of the equivalent generator averaged over the set G of generators is expressed as in the following equation (27A). Therefore, the mechanical input calculation unit 41 calculates the electrical output P E By substituting the second derivative of the electrical phase angle δ(t) in equation (27A) into the equation of motion of the equivalent generator shown in equation (2), the mechanical input P is calculated according to the following equation (27B): M Furthermore, the mechanical input calculation unit 41 passes the calculation result of the mechanical input through a low-pass filter to calculate the final mechanical input PM (t) may also be used.

[0174]

number

[0175] 16 , the frequency abnormality prevention unit 42 of the fifth embodiment performs load restriction to maintain the grid frequency when a generator trip is detected. Specifically, the frequency abnormality prevention unit 42 includes a frequency drop determination unit 60, a mechanical input drop determination unit 65, and a trip command unit 70.

[0176] The frequency drop determination unit 60 determines whether the drop in the electrical frequency F(t) of the equivalent generator calculated by the frequency calculation unit 40 continues for a threshold time. The mechanical input drop determination unit 65 determines whether the mechanical input P calculated by the mechanical input calculation unit 41 continues for a threshold time. M It is determined whether the decrease in (t) continues for a threshold time.

[0177] As a specific example of the configuration, the frequency drop determination unit 60 includes a drop detection unit 61, a reference value setting unit 62, and a timer unit 63. The drop detection unit 61 detects a drop in the electrical frequency F(t) by comparing the current electrical frequency F(t) with a frequency reference value set in the reference value setting unit 62. The timer unit 63 determines whether the drop in the electrical frequency F(t) has continued for a threshold time. Here, the reference value for the electrical frequency is, for example, a moving average value of the electrical frequency F(t) up to the present time.

[0178] As a specific example of the configuration, the mechanical input decrease determination unit 65 includes a decrease detection unit 66, a reference value setting unit 67, and a timer unit 68. The decrease detection unit 66 compares the current mechanical input with the reference value of the mechanical input set in the reference value setting unit 67 to determine the mechanical input P M The timer unit 68 detects a decrease in the mechanical input P M It is determined whether the decrease in (t) has continued for a threshold time. Here, the reference value of the mechanical input is the mechanical input PM The moving average of (t) is used.

[0179] The shutoff command unit 70 determines the electrical frequency F(t) and the mechanical input P based on the outputs of the timer units 63 and 68. M The shutdown command unit 70 determines whether both the electrical frequency F(t) and the mechanical input P(t) are continuously decreasing. M When both (t) and (t) are continuously decreasing, one or more of the loads Li (i=1 to n) are selected, and a command to break the circuit breaker CBi is output to the load control terminal device 56_i corresponding to the selected load Li.

[0180] [Effects of the fifth embodiment] As described above, the frequency calculation unit 40 of the power system stabilization device 55 of the fifth embodiment calculates the rotation speed n of each generator GAi (i=1 to n). i The electrical frequency F(t) of the equivalent generator GA is calculated with high accuracy based on the actual measurement data. The frequency anomaly prevention unit 42 of the power system stabilization device 55 determines a frequency anomaly based on the increase or decrease in this highly accurate electrical frequency F(t), thereby achieving highly accurate frequency anomaly prevention control.

[0181] In the prior art, as described above, the frequency was calculated from the bus voltage, so when there was variation in the rotation speed of multiple generators GAi, the frequency calculation result differed depending on the measurement point on the bus. In this embodiment, the rotation speed n of generators GAi (i = 1 to n) is calculated. i The inertia constant M of the generator GAi for the actual measured value Ai The average value of the rotation speed n(t) and the average value of the electrical frequency F(t) are calculated by weighted averaging using the formula, so the influence of variations can be removed.

[0182] Furthermore, the mechanical input calculation unit 41 of the system stabilization device 55 of the fifth embodiment calculates the second-order differential of the phase angle δ based on the numerical time differential of the average rotation speed n(t), and compares the calculated second-order differential of the phase angle δ with the voltage data v of each generator GAi (i = 1 to n). i (t) and current data i i(t) based on the total electrical output P E The mechanical input of the equivalent generator is calculated by substituting ρ and ρ into the equation of motion of the equivalent generator. Based on this mechanical input, it is possible to accurately determine whether the generator has fallen off.

[0183] In the prior art, as described above, the electrical output is assumed to be equal to the mechanical input, and the tripping of a generator is determined based on the electrical output, which poses a problem of not being able to detect the tripping of the second and subsequent generators for which the above assumption does not hold. The frequency anomaly prevention unit 42 of the power system stabilization device 55 of the fifth embodiment can accurately determine the tripping of a generator based on the mechanical input calculated by the mechanical input calculation unit 41.

[0184] Embodiment 6 [Outline of the sixth embodiment] In the sixth embodiment, a frequency abnormality prevention unit 42 having a different configuration from that of the fifth embodiment will be described. The frequency abnormality prevention unit 42 of the sixth embodiment calculates the electric frequency F and the electric output P of the generator that are a specified time ahead of the present time. E and sets the load control amount or the generator control amount based on this estimated value. This makes it possible to reliably maintain the frequency of the power system within the target frequency range after the system disturbance. This will be described in detail below with reference to the drawings.

[0185] An example of the power system to which the power system stabilization device of the sixth embodiment is applied is the same as the power system of the fifth embodiment shown in FIG.

[0186] [Details of frequency anomaly prevention unit operation] Fig. 17 is a block diagram showing an example of the functional configuration of the frequency abnormality prevention unit 42 in the system stabilization device 55 according to the sixth embodiment. Fig. 17 also shows the rotation speed data acquisition unit 31, the voltage / current data acquisition unit 32, the frequency calculation unit 40, and the mechanical input calculation unit 41 shown in Fig. 3.

[0187] 17, the frequency abnormality prevention unit 42 includes a frequency estimation unit 80, an electric output estimation unit 81, a control amount calculation unit 82, and a shutdown command unit 83.

[0188] At time t1 after the generator trips, the frequency estimator 80 executes a process to estimate the electrical frequency at time t2, a specified time after the time t1. Here, time t1 is the timing to start executing a control calculation for setting the load control amount. Time t2 is the timing to implement load control using the set load control amount. Alternatively, at time t1 after the load trips, the frequency estimator 80 executes a process to estimate the electrical frequency at time t2, a specified time after the time t1. Here, time t1 is the timing to execute a control calculation for setting the generator control amount, and time t2 is the timing to implement control using the set generator control amount.

[0189] Specifically, as shown in the following equation (28A), the frequency deviation between the electrical frequency F(t1) calculated by the frequency calculation unit 40 at time t1 and the reference frequency F0 is defined as ΔF(t1). The frequency estimation unit 80 uses this frequency deviation ΔF(t1) and the rate of change dF(t1) / dt of the electrical frequency at time t1 to calculate the frequency deviation ΔF between the electrical frequency F(t2) at time t2 and the reference frequency F0 according to the following equation (28B). EST Therefore, the electrical frequency F(t2) at time t2 is calculated by subtracting the reference frequency F0 from the estimated frequency deviation ΔF as shown in the following equation (28C): EST It is expressed as the sum of (t2).

[0190]

number

[0191] Although the above equation (28B) approximates the frequency deviation ΔF(t) as a linear function, other approximation equations such as polynomial approximation may also be used. More generally, the frequency estimator 80 estimates the electrical frequency F(t2) at a future time t2 based on the change in the value of the electrical frequency F(t) up to time t1.

[0192] The electrical output estimation unit 81 calculates the total electrical output P at time t1 based on the data acquired by the voltage and current data acquisition unit 32. E (t1) (i.e., the electrical output of an equivalent generator obtained by condensing multiple generators), the frequency deviation ΔF(t1) at time t1, and the estimated value of the frequency deviation ΔF at time t2. EST (t2) and the load frequency characteristic coefficient K L [pu / Hz], the electrical output P at time t2 is calculated according to the following equation (29): E Estimate (t2).

[0193]

number

[0194] The physical meaning of the above equation (29) is explained below. If we ignore losses in the lines, etc., the total electrical output P E and the total load value P L The initial value of the total load is P L0 [pu], and the load frequency characteristic coefficient is K L [pu / Hz], the total load when the frequency changes by ΔF is "P L0 (1+K L Therefore, the total electrical output P at time t1 is E The total load that balances at (t1) is P L0 (1+K L ΔF(t1)) and the total electrical output P estimated at time t2 E The total load that balances at (t2) is P L0 (1+K L ΔF EST (t2)), the above equation (29) is obtained as a result.

[0195] The control amount calculation unit 82 first calculates the mechanical input P of each generator GAi at time t1. Mi The total value of P M(i.e., the mechanical input of an equivalent generator obtained by condensing multiple generators) is obtained from the mechanical input calculation unit 41. Here, since the time from time t1, which is the control calculation timing, to time t2, which is the control execution timing, is short, the change due to the governor control of the generator GA can be ignored. In this case, the total value P of the mechanical input at time t1 M (t1) is the total mechanical input P at time t2 M (t2), the total mechanical input P at time t2 can be calculated by using the above equation (27). M (t2) is expressed by the following equation (30).

[0196]

number

[0197] Next, the control amount calculation unit 82 calculates the load control amount P LCS In addition, the control amount calculation unit 82 calculates the generator control amount P GCS is calculated according to the following equation (31B). In the following equations (31A) and (31B), k v is an adjustment coefficient for avoiding insufficient control due to voltage changes during load control or generator control. In other words, the load control amount or generator control amount at time t2 is determined based on the difference between the value obtained by multiplying the estimated total electrical output by the adjustment coefficient and the total mechanical input. The adjustment coefficient k v is stored in advance in the memory of the power system stabilization device 55.

[0198]

number

[0199] The tripping command unit 83 receives the load control amount P LCSThe shutdown command unit 83 outputs a shutdown command to one or more corresponding load control terminal devices 56 so as to shed one or more loads having a load amount equivalent to the generator control amount P GCS The fault detection terminal device 54 outputs a shutdown command to shut off one or more generators having an electrical output corresponding to the fault detection terminal device 54.

[0200] [Effects of the Sixth Embodiment] As described above, the frequency abnormality prevention unit 42 of the system stabilization device 55 of the sixth embodiment calculates the highly accurate electrical frequency F(t) calculated by the frequency calculation unit 40 and the highly accurate mechanical input P calculated by the mechanical input calculation unit 41. M Based on (t), it is possible to accurately calculate an appropriate load control amount or generator control amount at the control execution timing.

[0201] Various aspects of the present disclosure are summarized below as appendices.

[0202] (Appendix 1) a rotation speed data acquisition unit that acquires actual measurement data of rotation speeds of a plurality of generators on its own end side of the power system in a time series manner; a voltage and current data acquisition unit that acquires detection data of output voltages and output currents of the plurality of generators in time series; a phase angle deviation calculation unit that calculates, in a time series manner, a phase angle deviation from an initial value of a phase angle of an equivalent generator obtained by condensing the plurality of generators based on actual measurement data of the rotational speeds of the plurality of generators; and a step-out prevention unit that predicts the occurrence of step-out of the equivalent generator based on fluctuations in the calculated phase angle deviation, and outputs a shut-off command to one or more generators among the plurality of generators when the occurrence of step-out is predicted.

[0203] (Appendix 2) the step-out prevention unit includes a first response control unit for dealing with a first wave and a second wave of fluctuation of the phase angle deviation, The first response control unit calculating the electrical output of the equivalent generator in a time series manner based on the detected data of the output voltages and output currents of the plurality of generators; estimating a power phase difference angle curve when the power system is simulated by a one-machine infinite bus model based on the calculated phase angle deviation and the electrical output of the equivalent generator; 2. A power system stabilization device according to claim 1, configured to predict the occurrence of step-out of the equivalent generator based on the estimated power phase difference angle curve.

[0204] (Appendix 3) the step-out prevention unit further includes a second response control unit for dealing with fluctuations of the phase angle deviation from a third wave onward; The second response control unit calculating the electrical output of the equivalent generator in a time series manner based on the detected data of the output voltages and output currents of the plurality of generators; estimating an inertia constant, a damping coefficient, and a mechanical input of an equivalent generator at the other end when the power system is simulated by a two-machine system model based on the calculated phase angle deviation and the electrical output of the equivalent generator; determining an equation of motion of an equivalent generator in a one-machine infinite bus model that is equivalent in stability to the two-machine system model based on the estimated inertia constant, damping coefficient, and mechanical input of the equivalent generator at the other end; 3. The system stabilization device according to claim 1, configured to predict the occurrence of step-out based on the determined equation of motion.

[0205] (Appendix 4) the step-out prevention unit further includes a third response control unit for dealing with a weak braking phenomenon; The third response control unit calculating a damping coefficient representing the degree of change over time in the oscillation amplitude of the phase angle deviation; The power system stabilization device according to any one of appendices 1 to 3, configured to suppress a weak-damping phenomenon by outputting a shutdown command to one or more generators among the plurality of generators when the damping coefficient exceeds a threshold value.

[0206] (Appendix 5) the power system stabilization device further includes a step-out isolation unit that determines whether the plurality of generators are in a step-out state and isolates the plurality of generators from the power system when the plurality of generators are in a step-out state; The out-of-step separation unit Calculating an initial value of the phase angle of the equivalent generator based on detection data of output voltages and output currents of the plurality of generators; calculating a current phase angle of the equivalent generator by adding the phase angle deviation to the initial value of the phase angle; 5. The system stabilization device according to any one of appendices 1 to 4, configured to determine that the plurality of generators are in a step-out state when the current phase angle of the equivalent generator exceeds a threshold value.

[0207] (Appendix 6) The power system stabilization device a frequency calculation unit that calculates an electrical frequency of the equivalent generator in a time series manner based on actual measured values ​​of the rotational speeds of the plurality of generators; The system stabilization device according to any one of appendices 1 to 5, further comprising a frequency abnormality prevention unit that determines an abnormality in the frequency of the power system based on the electrical frequency and commands power supply restriction or load restriction.

[0208] (Appendix 7) the power system stabilization device further includes a mechanical input calculation unit that calculates a mechanical input of the equivalent generator in a time series manner, The mechanical input calculation unit calculating an average value of the rotation speeds of the plurality of generators in a time series manner by weighting and averaging the actual measured values ​​of the rotation speeds of the plurality of generators with the inertia constants of the plurality of generators; calculating a second-order differential of the phase angle of the equivalent generator in a time series manner based on the numerical time differential of the average value of the rotational speed; calculating the electrical output of the equivalent generator in a time series manner based on the detected data of the output voltages and output currents of the plurality of generators; 7. The power system stabilization device according to claim 6, configured to calculate the mechanical input power in a time series manner by substituting the second-order derivative of the phase angle and the electrical output power into an equation of motion of the equivalent generator.

[0209] (Appendix 8) 8. The power system stabilization device according to claim 7, wherein the frequency abnormality prevention unit implements load restriction when the electrical frequency of the equivalent generator calculated by the frequency calculation unit is continuously decreasing and the mechanical input of the equivalent generator calculated by the mechanical input calculation unit is continuously decreasing.

[0210] (Appendix 9) The frequency abnormality prevention unit estimating an electrical frequency of the equivalent generator at a second time in the future based on a change in the value of the electrical frequency of the equivalent generator up to a first time; estimating an electrical output of the equivalent generator at the second time based on an electrical output of the equivalent generator at the first time, a deviation between an electrical frequency at the first time and a reference frequency, and a deviation between an estimated value of the electrical frequency at the second time and the reference frequency; 9. The power system stabilization device according to claim 7, configured to calculate a load control amount or a generator control amount based on a deviation between a value obtained by multiplying the estimated electrical output by a regulation coefficient and the mechanical input of the equivalent generator calculated at the first time.

[0211] (Appendix 10) a rotation speed data acquisition unit that acquires actual measurement data of rotation speeds of a plurality of generators on its own end side of the power system in a time series manner; a voltage and current data acquisition unit that acquires detection data of output voltages and output currents of the plurality of generators in time series; a phase angle deviation calculation unit that calculates, in a time series manner, a phase angle deviation from an initial value of a phase angle of an equivalent generator obtained by condensing the plurality of generators based on actual measurement data of the rotational speeds of the plurality of generators; a step-out isolation unit that determines whether the plurality of generators are in a step-out state and isolates the plurality of generators from the power grid when the plurality of generators are in a step-out state; The out-of-step separation unit Calculating an initial value of the phase angle of the equivalent generator based on detection data of output voltages and output currents of the plurality of generators; calculating a current phase angle of the equivalent generator by adding the phase angle deviation to the initial value of the phase angle; A power system stabilization device configured to determine that the plurality of generators are in a step-out state when a current phase angle of the equivalent generator exceeds a threshold value.

[0212] (Appendix 11) a rotation speed data acquisition unit that acquires actual measurement data of rotation speeds of a plurality of generators on its own end side of the power system in a time series manner; a voltage and current data acquisition unit that acquires detection data of output voltages and output currents of the plurality of generators in time series; a frequency calculation unit that calculates, in a time series manner, an electrical frequency of an equivalent generator obtained by condensing the plurality of generators based on actual measured values ​​of the rotational speeds of the plurality of generators; a frequency abnormality prevention unit that determines an abnormality in the frequency of the power system based on the electrical frequency and commands power supply restriction or load restriction.

[0213] (Appendix 12) the power system stabilization device further includes a mechanical input calculation unit that calculates a mechanical input of the equivalent generator in a time series manner, The mechanical input calculation unit calculating an average value of the rotation speeds of the plurality of generators in a time series manner by weighting and averaging the actual measured values ​​of the rotation speeds of the plurality of generators with the inertia constants of the plurality of generators; calculating a second-order differential of the phase angle of the equivalent generator in a time series manner based on the numerical time differential of the average value of the rotational speed; calculating the electrical output of the equivalent generator in a time series manner based on the detected data of the output voltages and output currents of the plurality of generators; 12. The power system stabilization device of claim 11, configured to calculate the mechanical input power over time by substituting the second-order derivative of the phase angle and the electrical output power into an equation of motion of the equivalent generator.

[0214] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of this application is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0215] 1,51 power plant, 2 substation, 3,55 system stabilization device, 4 multi-machine system, 10 input converter, 11 sample-and-hold circuit, 12 multiplexer, 13 A / D converter, 14 CPU, 15 RAM, 16 ROM, 17 auxiliary storage device, 18 input / output interface, 19 communication device, 20 bus, 21 calculation processing unit, 31 rotation speed data acquisition unit, 32 current data acquisition unit, 33 phase angle deviation calculation unit, 34 step-out prevention unit, 35 first and second wave response control unit, 36 Nth wave response control unit, 37 weak braking response control unit, 38 step-out separation unit, 40 frequency calculation unit, 41 mechanical input calculation unit, 42 frequency abnormality prevention unit, 50 system stabilization system, 52, F1, F2 transmission line, 53 main system, 54 fault detection terminal unit, 56 load control terminal unit, 60, 65 Decrease determination unit, 61, 66 Decrease detection unit, 62, 67 Reference value setting unit, 63, 68 Timer unit, 70, 83 Trip command unit, 80 Frequency estimation unit, 81 Electrical output estimation unit, 82 Control amount calculation unit, B1 Power plant bus (measurement bus), B2 Substation bus, BA bus, BG Generator bus, CB Circuit breaker, CT Current transformer, E A ,E B Back voltage (internal voltage), F electrical frequency, F0 reference frequency, Fi frequency, GA generator, I A Self-end current, J A Acceleration energy, J D Deceleration energy, K L Load frequency characteristic coefficient, L Load, M A Inertia constant, MTr1,MTrn transformer, PE Electrical power, P GCS Generator control amount, P LCS Load control amount, P M Mechanical input, Q E Reactive power, V A Self-terminal voltage, X A Internal reactance, X L Line reactance, i i Current data, k v Adjustment factor, n i Rotation speed, v i Voltage data, δ phase angle, Δδ phase angle deviation.

Claims

1. a rotation speed data acquisition unit that acquires actual measurement data of rotation speeds of a plurality of generators on its own end side of the power system in a time series manner; a voltage and current data acquisition unit that acquires detection data of output voltages and output currents of the plurality of generators in time series; a phase angle deviation calculation unit that calculates, in a time series manner, a phase angle deviation from an initial value of a phase angle of an equivalent generator obtained by condensing the plurality of generators based on actual measurement data of the rotational speeds of the plurality of generators; and a step-out prevention unit that predicts the occurrence of step-out of the equivalent generator based on fluctuations in the calculated phase angle deviation, and outputs a shutdown command to one or more generators among the plurality of generators when the occurrence of step-out is predicted.

2. the step-out prevention unit includes a first response control unit for dealing with a first wave and a second wave of fluctuation of the phase angle deviation, The first response control unit calculating the electrical output of the equivalent generator in a time series manner based on the detected data of the output voltages and output currents of the plurality of generators; estimating a power phase difference angle curve when the power system is simulated by a one-machine infinite bus model based on the calculated phase angle deviation and the electrical output of the equivalent generator; The grid stabilization device according to claim 1 , configured to predict occurrence of step-out of the equivalent generator based on the estimated power phase difference angle curve.

3. the step-out prevention unit further includes a second response control unit for dealing with fluctuations of the phase angle deviation from a third wave onward; The second response control unit calculating the electrical output of the equivalent generator in a time series manner based on the detected data of the output voltages and output currents of the plurality of generators; estimating an inertia constant, a damping coefficient, and a mechanical input of an equivalent generator at the other end when the power system is simulated by a two-machine system model based on the calculated phase angle deviation and the electrical output of the equivalent generator; determining an equation of motion of an equivalent generator in a one-machine infinite bus model that is equivalent in terms of stability to the two-machine system model based on the estimated inertia constant, damping coefficient, and mechanical input of the equivalent generator at the other end; The system stabilization device according to claim 2 , configured to predict the occurrence of a step-out based on the determined equation of motion.

4. the step-out prevention unit further includes a third response control unit for dealing with a weak braking phenomenon, The third response control unit calculating a damping coefficient representing the degree of change over time in the oscillation amplitude of the phase angle deviation; 4. The power system stabilization device according to claim 3, configured to suppress a weak-damping phenomenon by outputting a shutdown command to one or more generators among the plurality of generators when the damping coefficient exceeds a threshold value.

5. the power system stabilization device further includes a step-out isolation unit that determines whether the plurality of generators are in a step-out state and isolates the plurality of generators from the power system when the plurality of generators are in a step-out state; The out-of-step separation unit Calculating an initial value of the phase angle of the equivalent generator based on detection data of output voltages and output currents of the plurality of generators; calculating a current phase angle of the equivalent generator by adding the phase angle deviation to the initial value of the phase angle; The system stabilization device according to any one of claims 1 to 4, configured to determine that the plurality of generators are in a step-out state when a current phase angle of the equivalent generator exceeds a threshold value.

6. The power system stabilization device includes: a frequency calculation unit that calculates an electrical frequency of the equivalent generator in a time series manner based on actual measured values ​​of the rotational speeds of the plurality of generators; The system stabilization device according to any one of claims 1 to 4, further comprising: a frequency abnormality prevention unit that determines an abnormality in the frequency of the power system based on the electrical frequency and commands power supply limiting or load limiting.

7. the power system stabilization device further includes a mechanical input calculation unit that calculates a mechanical input of the equivalent generator in a time series manner, The mechanical input calculation unit calculating an average value of the rotation speeds of the plurality of generators in a time series manner by weighting and averaging the actual measured values ​​of the rotation speeds of the plurality of generators with the inertia constants of the plurality of generators; calculating a second-order differential of the phase angle of the equivalent generator in a time series manner based on the numerical time differential of the average value of the rotational speed; calculating the electrical output of the equivalent generator in a time series manner based on the detected data of the output voltages and output currents of the plurality of generators; 7. The system stabilizer according to claim 6, configured to calculate the mechanical input power in a time series manner by substituting the second derivative of the phase angle and the electrical output power into an equation of motion of the equivalent generator.

8. 8. The grid stabilization device according to claim 7, wherein the frequency abnormality prevention unit implements load restriction when the electrical frequency of the equivalent generator calculated by the frequency calculation unit is continuously decreasing and the mechanical input of the equivalent generator calculated by the mechanical input calculation unit is continuously decreasing.

9. The frequency abnormality prevention unit estimating an electrical frequency of the equivalent generator at a second time in the future based on a change in the value of the electrical frequency of the equivalent generator up to a first time; estimating an electrical output of the equivalent generator at the second time based on an electrical output of the equivalent generator at the first time, a deviation between an electrical frequency at the first time and a reference frequency, and a deviation between an estimated value of the electrical frequency at the second time and the reference frequency; 8. The grid stabilization device according to claim 7, configured to calculate a load control amount or a generator control amount based on a deviation between a value obtained by multiplying the estimated electrical output by an adjustment coefficient and the mechanical input of the equivalent generator calculated at the first time.

10. a rotation speed data acquisition unit that acquires actual measurement data of rotation speeds of a plurality of generators on its own end side of the power system in a time series manner; a voltage and current data acquisition unit that acquires detection data of output voltages and output currents of the plurality of generators in time series; a phase angle deviation calculation unit that calculates, in a time series manner, a phase angle deviation from an initial value of a phase angle of an equivalent generator obtained by condensing the plurality of generators based on actual measurement data of the rotational speeds of the plurality of generators; a step-out isolation unit that determines whether the plurality of generators are in a step-out state and isolates the plurality of generators from the power grid when the plurality of generators are in a step-out state; The out-of-step separation unit Calculating an initial value of the phase angle of the equivalent generator based on detection data of output voltages and output currents of the plurality of generators; calculating a current phase angle of the equivalent generator by adding the phase angle deviation to the initial value of the phase angle; A power system stabilization device configured to determine that the plurality of generators are in a step-out state when a current phase angle of the equivalent generator exceeds a threshold value.

11. a rotation speed data acquisition unit that acquires actual measurement data of rotation speeds of a plurality of generators on its own end side of the power system in a time series manner; a voltage and current data acquisition unit that acquires detection data of output voltages and output currents of the plurality of generators in time series; a frequency calculation unit that calculates, in a time series manner, an electrical frequency of an equivalent generator obtained by condensing the plurality of generators based on actual measured values ​​of the rotational speeds of the plurality of generators; a frequency abnormality prevention unit that determines an abnormality in the frequency of the power system based on the electrical frequency and commands power supply restriction or load restriction.

12. the power system stabilization device further includes a mechanical input calculation unit that calculates a mechanical input of the equivalent generator in a time series manner, The mechanical input calculation unit calculating an average value of the rotation speeds of the plurality of generators in a time series manner by weighting and averaging the actual measured values ​​of the rotation speeds of the plurality of generators with the inertia constants of the plurality of generators; calculating a second-order differential of the phase angle of the equivalent generator in a time series manner based on the numerical time differential of the average value of the rotational speed; calculating the electrical output of the equivalent generator in a time series manner based on the detected data of the output voltages and output currents of the plurality of generators; The system stabilizer according to claim 11, configured to calculate the mechanical input power in a time series manner by substituting the second derivative of the phase angle and the electrical output power into an equation of motion of the equivalent generator.

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