JP2647088B2 - Step-out prediction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an out-of-step prediction device capable of predicting and determining out-of-step of a power system at an early stage.

(Prior art) Conventionally, as a means for detecting a step-out of a system due to a power system accident or the like, a voltage phase angle between electric stations at both ends of a transmission line of a power system is compared, and a difference between the two is determined. There is a method of detecting that the electrical angle has become, for example, 180 degrees or more and determining that the step-out occurs. However, such a means delays step-out detection, so that even if various system stabilization controls are performed under these conditions, there is a risk that step-out phenomena may spread to other parts due to a delay in control time.

(Problems to be Solved by the Invention) As described above, in the conventional method, it is not possible to early detect that the power system is out of step, and as a result, the out-of-step phenomenon spreads to other parts. There was a problem.

SUMMARY OF THE INVENTION An object of the present invention is to provide a step-out prediction device capable of predicting and measuring early and with high accuracy that a power system will step out.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the step-out prediction device according to the present invention has an accident in a power system including a plurality of generators. Then, using the electrical output of each generator detected at a predetermined time interval, the angular velocity detection means for detecting the angular velocity of each generator, and when the accident of the power system is removed,
Using the angular velocities of each generator at a plurality of times from the angular elimination transmitted from the angular velocity detection means through the transmission means to the current time after the removal of the accident, find a coefficient of a preset estimation formula, and then use this estimation formula An angular velocity prediction means for obtaining an estimated value of the angular velocity of each generator; and an energy prediction means for obtaining a predicted value of the kinetic energy of the entire power system by using the estimated value of the angular velocity of each generator obtained by the angular velocity prediction means. Based on the predicted value of the kinetic energy of the entire power system obtained by the energy predicting means, the predicted value of the kinetic energy increases, the predicted value of the potential energy decreases, and the difference between the two is set to a predetermined threshold value. And step-out determination means for determining that the power system has stepped out on the condition that the power loss has been exceeded.

(Operation) In the above-mentioned step-out prediction device, when an accident occurs in the power system, the angular velocities of the respective generators in the system are detected by the angular velocity detection means, respectively, and transmitted to the angular velocity prediction means via the transmission means. Then, when the system fault is removed, the angular velocity prediction means predicts the future value of the angular velocity of each generator. In the energy prediction means, a predicted value of the kinetic energy of the entire power system is obtained based on each predicted transmission. Further, in the step-out determination means, the change tendency based on the kinetic energy of the entire power system predicted by the energy prediction means, that is, the predicted value of the kinetic energy is increased and the magnitude thereof is set to a predetermined threshold. By detecting the exceeding, it is determined that the power system is out of synchronization.

Embodiment First, the concept of step-out determination according to the present invention will be described.

Methods for determining the out-of-step of the power system include a method using electrical information such as voltage and current, and a method using energy accumulated in the system due to a power system accident or the like. In particular, the latter is known as the energy method or the Lyapunov method. According to the present invention, this energy method is used for step-out determination.

That is, equation (1) shows an example of the energy function.
In equation (1), the first term on the right side is the kinetic energy of the entire system, and the second term on the right side is the potential energy of the entire system.
The subscript i indicates each generator, and the subscript COI indicates various quantities of the center of inertia weighted by the inertia constant of the generator.

P _ai = P _INi −P _ei … (2e) The symbols on the right side of the equations (2a) to (2f) mean the following, respectively.

M: inertia constant of generator, ω: angular velocity of generator, δ: internal phase angle of generator, PIN: mechanical input to generator, Pe: electrical output of generator, n: power generation incorporated into system Number of machines operating.

FIGS. 2 (a) and 2 (b) show examples of temporal movement of kinetic energy (hereinafter, referred to as KE) and potential energy (hereinafter, referred to as PE) when a three-phase short circuit accident or the like occurs in the power system. 2 (a) shows a case where the system is stable, and FIG. 2 (b) shows a case where the system is unstable (a part of the system loses synchronism). Now, it is known that the total energy obtained by adding KE and PE is constant. As can be seen from FIGS. 2 (a) and 2 (b), the energy accumulated due to the system fault becomes KE and PE after the fault is eliminated. Share with PE. In a stable case, since the system absorbs the KE during the accident, the PE increases and the KE decreases. On the other hand, when unstable, the KE increases and becomes unstable because the system does not have the ability to absorb the KE during the accident. Accordingly, by quickly capturing such characteristics of KE and PE by means of prediction, it is possible to perform quick and appropriate out-of-step determination. In the present invention, KE and PE
The step-out determination is performed by predicting the movement of the KE. That is, specifically, when the predicted value of the KE after the removal of the accident increases and its magnitude exceeds a preset threshold value, it is determined that the system is out of synchronization.

Next, a specific calculation method of the energy value will be described.

First, in a steady state before the occurrence of the accident, the electrical output Pei (0) of each generator is detected, and the value is used as the mechanical input PINi of each generator. Next, if an accident occurs in the system, the angular velocity ωi is calculated from the equation of motion shown in equation (3) using the electrical output Pei of each generator detected at intervals of Δt.

_{ω i (t) = ω i} (t-Δt) + (P INi -P ei (t)) Δt / M i ... (3) Next, the detection value of the angular velocity which is calculated up to the present time t ₀ ω _{i (to )} , ω _i (to−Δt), ω _i (to−2 · Δt),..., ω _i (to−m · Δt), and is set in advance by the least square method as shown in FIG. The coefficients of the estimation formula are calculated, and the angular velocity ωi ^* at the future time is obtained at Δt intervals as a point on the extension of the estimation formula.
For example, the case where the estimation expression is a quadratic expression represented by Expression (4) will be described.

ω _i ^* _(t) = C ₁ t ² + C ₂ t + C ₃ (4) First, using the detected values of ωi up to the present time, the coefficients C ₁ , C ₂ , and C ₃ of the estimation formula are obtained by the least square method. . Next, (5)
An estimated time is set for each Δt interval according to the equation, and the estimated time ωi ^* is calculated by substituting the estimated time into the equation (4).

t = t ₀ + n · Δt (5) (n = 1,..., ns) Here, t ₀ is the current time, and ns is the estimated number of times for each Δt interval.

Finally, the predicted value KE ^* of the kinetic energy is obtained from the equation (6) using the angular velocity ωi ^* of each generator estimated by the method described above.

Next, a method of determining out-of-step by using the predicted value KE ^* of the kinetic energy predicted as described above will be described.

FIG. 4 shows the movement of the KE when it is determined that the step-out occurs. Also, in the figure, KE indicates an operation value, and KE ^* indicates a predicted value.

First, it is determined whether or not KE ^* is increasing, using equation (7).

KE ^* (to + Δt) <KE ^* (to + 2Δt) <... <KE ^* (to + ns · Δt) (8) Next, a threshold value El for which the prediction value at the final prediction time is set in advance by the equation (8) is It is determined whether or not it has exceeded. If these equations (7) and (8) are simultaneously satisfied, it is finally determined that the step-out occurs.

KE ^* (to + ns · Δt)> El (8) FIG. 5 is an overall flowchart of the step-out determination method according to the present invention described above. As described above, in the present invention, the kinetic energy of the entire power system, which is an index of whether or not a step-out phenomenon of the power system occurs, is based on the output (angular velocity) of the generator before and after the occurrence of the power system accident. The calculation is performed online, and a short-term future change is predicted using the calculated value, and the step-out phenomenon of the power system is determined early (determination of stability) from the change tendency.

Hereinafter, an embodiment of the present invention based on the above-described concept will be described with reference to the drawings.

FIG. 1 shows a configuration example of a power system to which a step-out prediction device of the present invention is applied. In FIG. 1, reference numeral 1 denotes a target power system, G1 and G2 denote generators incorporated into the power system 1, and B1 and B2 denote buses on the generators G1 and G2 side. Meanwhile, 21,2
2 by using an electrical output P _1, P ₂ of each generator G1, G2, which is measured via the transformer and a current transformer meter (not shown), the angular velocity of each generator G1, G2 for the incorporation into the system Angular velocity detecting means for detecting ωi, 31 and 32 are transmitting means for transmitting the detection signals from the angular velocity detecting means 21 and 22, respectively, and 4 are the detecting signals transmitted via the transmitting means 31 and 32, respectively. Angular velocity prediction means for predicting the future value based on the angular velocity of each of the generators G1 and G2, and 5 based on the predicted value of the angular velocity predicted by the angular velocity prediction means 4, Energy prediction means 6 for obtaining a future predicted value of kinetic energy, based on the kinetic energy of the entire future system predicted by the energy prediction means 5,
The step-out determining means determines that the system is out of step on the condition that the predicted value of the kinetic energy increases and the magnitude of the predicted value exceeds a preset threshold value.

Next, the operation of the step-out prediction device configured as described above will be described.

First, in the steady state, each of the generators G1, G
The electrical output of the generator 2 is measured via an unillustrated instrument transformer and current transformer, and the value is stored as the mechanical input PINi of each of the generators G1 and G2 (step S1 in FIG. 5).

Next, when an accident occurs in the power system 1 in such a state, the electric output Pei of the generators G1 and G2 is set in the same manner as in the steady state.
(T) is detected at intervals of .DELTA.t, and using this, the angular speeds .omega.i of the generators G1, G2 are detected by the speed detecting means 21, 22, respectively (step S2 in FIG. 5). Is transmitted to the angular velocity prediction means 4 via

Next, when the system fault is eliminated, the angular velocity predicting means 4 obtains the estimated values ωi ^* of the angular velocities of the generators G1 and G2 by the operation of steps S3 and S4 in FIG. Can be The energy predicting means 5 obtains the predicted value KE ^* of the kinetic energy of the entire system by the operation of step S5 in FIG. 5 using the estimated value of the angular velocity ωi ^* , and gives the result to the step-out determining means 6. Can be Further, in the step-out determination means 6, the energy prediction means 5
Using the predicted value KE ^* of the kinetic energy predicted in step (1), the step-out determination of the power system 1 is performed by the operation of step S6 in FIG. As a result, when it is determined that the system is out of synchronization, a determination result is output to a system stabilization device (not shown) (step S7 in FIG. 5), and system stabilization control is performed to prevent system out-of-step. Will be prevented. If it is not determined that the step-out occurs, the process returns to step S2 in FIG. 5, and the above-described step-out determination is continuously performed for a certain period after the occurrence of the accident.

As described above, the step-out prediction device according to the present embodiment has two steps.
Each of the generators G1, G2 is used by using the electrical output of each of the generators G1, G2 in the power system 1 including the two generators G1, G2.
Angular velocity detecting means 21 and 22 for respectively detecting the angular velocity ωi of
The angular velocities ωi of the generators G1 and G2 transmitted from the angular velocity detecting means 21 and 22 via the transmitting means 31 and 32, respectively, are input,
An angular velocity predicting means 4 for predicting the future value; an energy predicting means 5 for obtaining a predicted value KE ^* of the kinetic energy of the entire system based on the angular velocity ωi ^* predicted by the angular velocity predicting means 4; based on the predicted value KE of kinetic energy overall predicted strains ^*, the estimated value of the kinetic energy KE ^* is increased and the system on condition that the size exceeds a preset threshold value El Since the system is provided with the out-of-step determining means 6 for determining out-of-step, it is possible to early detect that the power system 1 is out of step due to the occurrence of an accident. By performing some kind of system stabilization control using the system, it is possible to prevent the power system 1 from stepping out in advance. In other words, the out-of-step prediction device of the present embodiment grasps on-line the change in kinetic energy of the entire power system 1 and determines out-of-step based on the change tendency. Since the corresponding maximum potential energy change can be indirectly captured, the step-out phenomenon of the power system 1 can be determined early and with high accuracy.

Further, since only the kinetic energy is used, the amount of calculation is small, so that the load on the calculation device can be reduced.

In the above embodiment, for simplicity of description, the case where the number of generators incorporated into the power system 1 is two has been described. However, the present invention is not limited to this, and the present invention can be similarly applied to the case of three or more generators. Can be done.

In the above embodiment, the angular velocity detecting means 21 and 22 are
1, the angular velocity ω of the generators G1 and G2 is detected using the electrical output of G2. However, the same operation and effect as described above can be achieved by directly detecting the angular velocity ω from the rotation axes of the generators G1 and G2. Needless to say, this is obtained.

[Effects of the Invention] As described above, according to the present invention, when an accident occurs in an electric power system including a plurality of generators, the electrical output of each generator detected at predetermined time intervals is reduced. make use of,
Angular velocity detecting means for detecting the angular velocity of each generator, and each generator at a plurality of points in time from the removal of the accident to the current time after the accident is transmitted from the angular velocity detecting means via the transmission means when the power system fault is removed Calculate the coefficient of an estimation formula set in advance using the angular velocities described above, and then use this estimation formula to estimate angular velocity of each generator. Energy prediction means for obtaining a predicted value of the kinetic energy of the entire power system using the estimated value of the angular velocity of the power system, and a prediction of the kinetic energy based on the predicted value of the kinetic energy of the entire power system obtained by the energy prediction means. A step-out determining means for determining step-out of the power system on condition that the predicted value of the potential energy decreases and the difference between the two exceeds a preset threshold value; Since so as to constitute comprises, step-out predicting devices capable of the power system to predict the determination at an early stage and with high accuracy can lead to loss of synchronism can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a power system to which a step-out prediction device of the present invention is applied, and FIGS. 2 (a) and 2 (b) show temporal changes in energy when a three-phase short-circuit accident or the like occurs in the power system. FIG. 3 is a diagram showing a motion, FIG. 3 is a diagram for explaining a method of estimating a future angular speed motion based on the detected angular speed of the generator, and FIG. FIG. 5 is a flowchart for explaining the movement, and FIG. 5 is a flowchart for explaining the overall flow of the step-out determination method. 1 ... power system, 21,22 ... angular velocity detecting means, 31, 32 ...
Transmission means, 4 ... Angular velocity prediction means, 5 ... Energy prediction means, 6 ... Step-out determination means, G1, G2 ... Generators, B1, B2
...... Bus line.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Eiji Hioki 20-1 Kitasekiyama, Odaka-cho, Midori-ku, Nagoya-shi Within Chubu Electric Power Co., Inc. (72) Inventor Kazuya Omata Toshiba, Fuchu-shi, Tokyo No. 1 in the Toshiba Fuchu Plant Co., Ltd. (72) Inventor Masahiro Sato 1 in Toshiba-cho, Fuchu City, Tokyo Prefecture In the Toshiba Fuchu Plant Co., Ltd. (56) References JP-A-61-214726 (JP, A) 61-214728 (JP, A) Materials of the Technical Meeting of the Institute of Electrical Engineers of Japan. 109-118

Claims (1)

(57) [Claims] An out-of-step predicting apparatus for predicting out-of-step of a power system including a plurality of generators, wherein when an accident occurs in the power system, each of the power generations detected at predetermined time intervals is detected. Angular velocity detecting means for detecting the angular velocity of each of the generators, respectively, using the electrical output of the generator; and, when the accident of the power system is eliminated, the accident transmitted from the angular velocity detecting means via the transmission means. Using the angular velocities of the respective generators at a plurality of times from the removal to the present time, a coefficient of a preset estimation formula is obtained, and then, using this estimation formula, an angular velocity for obtaining an estimated value of the angular speed of the respective generators A prediction unit, an energy prediction unit that obtains a predicted value of a kinetic energy of the entire power system using an estimated value of the angular speed of each of the generators obtained by the angular speed prediction unit, Based on the calculated kinetic energy predicted value of the entire power system, the predicted value of the kinetic energy increased, the predicted value of the potential energy decreased, and the difference between the two exceeded a predetermined threshold. And a step-out determining means for determining that the step-out of the power system has occurred on the condition that: