JP2692793B2 - Power system out-of-step predictor - Google Patents

Description

Description: TECHNICAL FIELD [0001] The present invention relates to a power system out-of-step predicting device capable of predicting and determining a step-out of a power system in advance. [Technical background of the invention and its problems] Conventionally, as a means for preventing a step-out phenomenon between generators due to a system fault, voltage phases of a plurality of electric power stations are compared with each other, and the phase angle difference between them is electric. There is a step-out separation relay that opens a circuit breaker of each electric station by detecting that it has become 180 degrees or more at the corner and determines that it is out of step. However, with such means, there is a possibility that the out-of-step phenomenon may spread to other parts because the out-of-step detection is delayed. Therefore, if the out-of-step of the generator can be predicted and determined in advance, that is, if the out-of-step can be predicted and determined in advance, instead of detecting the out-of-step, various system stabilization controls can be performed under these conditions and It is possible to prevent the out-of-step in advance, but a means for detecting the internal voltage phase angle difference between the generators and predicting and determining the out-of-step early has not yet been realized. [Object of the Invention] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to predict and determine an outage of an electric power system at an early stage to prevent an outage between generators in advance. An object of the present invention is to provide an out-of-step predicting device for a power system that can prevent such a situation. [Outline of the Invention] In order to achieve the above-mentioned object, in a step-out prediction device for a power system of the present invention, a voltage at a terminal of each generator in a power system configured by linking a plurality of generators or in the vicinity thereof and Multiple voltage / current detectors that detect currents respectively, multiple positive-phase converters that convert the voltage and current values of the generator detected by these voltage / current detectors to positive-phase values, and this positive-phase converter A plurality of internal voltage detectors that detect the internal voltage of each generator based on the positive-phase voltage and the positive-phase current of the generator converted by the generator, and the generators detected by the internal voltage detectors. It is provided with a step-out judging device which inputs an internal voltage and predicts future step-out occurrence. Further, the internal voltage of each generator from each internal voltage detector, which is transmitted through the transmission system, is input to the above-mentioned step-out judging device to make the internal voltage phase angle difference between the generators constant period. Using the internal voltage phase angle difference detection means and the internal voltage phase angle difference at a plurality of past times detected by the internal voltage phase angle difference detection means, the relationship between the time and the internal voltage phase angle difference is calculated. The approximate formula of the curve shown is obtained, and from this approximate formula, the predictive calculation means for predicting and calculating the internal voltage phase angle difference at each time in the future, and the predicted internal voltage phase angle difference calculated by this predictive calculation means over time. There is provided a step-out determination means that shows a divergence tendency that increases with it, and determines that a step-out has occurred when it is determined that the value exceeds an allowable value. Embodiment of the Invention First, the concept of step-out prediction according to the present invention will be described. FIG. 4 is a diagram showing an example of an electric power system, which includes 1a and 1b.
Indicates generators in parallel with the power grid, respectively. Next, FIGS. 5 (a) to 5 (c) and 5 (d) show an outline of the manner in which the generator 1a in FIG. , Each generator 1
This is shown by the movement of the internal voltage vectors _A and _B of a and 1b and the movement of the internal voltage phase angle difference between them. Here, FIG. 5 (a) shows a normal state, and the generator 1a
And the generator 1b are operating with a certain phase angle difference θa. Next, Fig. 5 (b) shows the generator 1a and the generator due to system disturbance.
The movement of 1b is different and the phase angle difference gradually increases. Then, FIG. 5 (c) shows a case where the phase angle difference is increased more and more and the angle becomes 180 °. In such a state, the generator 1a may lose synchronism with the generator 1b and become out of sync. Further, FIG. 5 (d) shows a temporal change in the increasing tendency of the internal voltage phase angle difference between the generator 1a and the generator 1b as described above. That tendency becomes monotonous divergence. In this way, the step-out phenomenon can be captured by observing the change in the internal voltage phase angle difference between the generators. Next, the past two generators 1 detected in a fixed cycle 1
A method for predicting and calculating the internal voltage phase angle difference at a future time from the internal voltage phase angle difference between a and 1b will be described. Generally, when the accidental transmission line is cut off by the protective relay and the transient is subsided, the internal voltage phase angle difference between the generator 1a and the generator 1b does not change discontinuously due to the inertia of each generator. It changes smoothly. Therefore, it is possible to obtain a high-order expression that passes through the internal voltage phase angle differences at the past several points and obtain the future internal voltage phase angle differences as points on the extension thereof. Hereinafter, a case of predicting with a quadratic equation will be described with reference to FIG. Generator 1a and generator 1b detected now at ΔT intervals
Let θ (t _K ), θ (t _K-1 ), θ (t _K-2 ) be the internal voltage phase angle difference between and, and the curves that pass through these three points are equations (1) and (2). Is defined by θ (t) = θ (t _K-2 ) + Δθ ₁₂ (t−t _K-1 ) + Δθ _O12
(T-t _K-1 ) (t-t _K-2 ) (1) Where t _K is the current time, t _K-1 is the time before ΔT, and t _K-2 is 2
Times before ΔT are shown. Then, the internal voltage phase angle difference at the future time point τ is calculated by substituting τ at t in the equation (1). Next, a method of determining out-of-step will be described with reference to FIG. For the step-out determination, whether the internal voltage phase angle difference between the generator 1a and the generator 1b at the future time calculated by the equations (1) and (2) shows a diverging tendency and exceeds the preset boundary value. Depending on whether or not. That is, future time point τ ₁ <τ ₂ <…
If the internal voltage phase angle difference at <τ _P is θ (τ ₁ ) <θ (τ ₂ ) <... <θ (τ _P ) ... (3) and θ (τ _P )> θ limit ... (4) Determined as key. Here, θlimit is the boundary value described above. This step-out determination method is a physical property that, when the generator 1a accelerates step-out with respect to the generator 1b by, for example, the first wave, the internal voltage phase angle difference between the two monotonically diverges and exceeds a certain boundary value. Are using. Hereinafter, an embodiment of the present invention based on the above concept will be described with reference to the drawings. FIG. 1 shows an example of the configuration of a power system step-out prediction device according to the present invention. In the figure, 1a and 1b are generators connected in parallel to the power system as described above, and 2a and 2b are transformers PT.
a, PTb, current transformer CTa, CTb voltage / current detector that samples the voltage and current of each generator 1a, 1b at high speed, 3a, 3b are high speed voltage / current detectors 2a, 2b Positive phase converter that converts the voltage and current of the generator sampled into the positive phase value, 4a, 4b are the positive phase voltage and positive phase of the generator 1a, 1b output from this positive phase converter 3a, 3b It is an internal voltage detector that detects the internal voltage of the generators 1a, 1b based on the current value. Further, 5a and 5b are transmission systems for transmitting the internal voltage of the generators 1a and 1b detected by the internal voltage detectors 4a and 4b to the out-of-step judging device 6. Further, the out-of-step judging device 6 is composed of an internal voltage phase angle difference detecting section 6a and an out-of-step judging section 6b.
The internal voltage phase angle difference detection unit 6a is for detecting the phase angle difference between the two from the internal voltage of each generator 1a, 1b transmitted via the transmission system 5a, 5b, and the step-out determination unit 6b is The future internal voltage phase angle difference is predicted and calculated from the past several points of the phase angle difference, and the generator 1a is calculated according to the value and the tendency of change.
Alternatively, it predicts and determines a step out of 1b. Next, the operation of this configuration will be specifically described. In Fig. 1, when a system disturbance occurs due to a transmission line failure, etc., and the failure is removed by a protective relay (not shown) and a certain period of time elapses, the voltage / current detectors 2a, 2b are respectively set to the voltage of the generators 1a, 1b and The current is sampled at a high speed at intervals of ΔT, and the detected voltages and currents of the generators 1a and 1b are converted into positive phase values by the positive phase converters 3a and 3b.
For example, if the sampling rate is 600 Hz in the 50 Hz system, the sampling interval ΔT is about 1.67 [msec], and the current voltage and current sampling values are V (m) and I (m).
Then, the normal phase values V ₁ (m) and I ₁ (m) are calculated by the following equations (5) and (6), respectively. V ₁ (m) = {V _a (m) −V _b (m-2) + V _c (m-4)} / 3 (5) I ₁ (m) = {I _a (m) −I _b ( m-2) + V _c (m-4)} / 3 (6) where Va and Ia are a-phase voltage and current values, Vb and Ib are b-phase voltage and current values, and Vc and Ic are c The voltage and current values of the phase. Next, the internal voltage detectors 4a, 4b use the positive-phase voltage and the positive-phase current value of the generators 1a, 1b output from the positive-phase converters 3a, 3b to determine the internal voltage E _A , E of the generators 1a, 1b. Detect _B. For example,
In the case of 600 Hz sampling in the 50 Hz system, the current internal voltage E (m) is calculated by the following equation (7) using the positive phase voltage V ₁ and the positive phase current I ₁ detected above. E (m) = V ₁ (m) −I ₁ (m ₋₃ ) × Xq (7) where V ₁ (m) is the positive phase voltage of the current generator, and I
₁ (m _-3 ) is the generator's positive-phase current detected 3 samples before. Xq is the q-axis synchronous reactance of the generator. In addition, the internal voltage E of the generators 1a, 1b detected above
_A (m) and E _B (m) are out-of-step judging devices 6 via transmission systems 5a and 5b, respectively.
Is transmitted to As a result, in the internal phase angle difference detection unit 6a of 6 of the step-out determination device, as shown in FIG.
From the time difference Δξ when the internal voltages E _A and E _{B of} 1b cross the zero potential, the internal voltage phase angle difference θ between the two is calculated by the following equation at ΔT intervals. θ = 360 × f × Δξ (8) where f is the fundamental frequency of the system. Also, ΔT is
1 / 2f or 1 / f, for example, 10 [m in 50 (Hz) system
sec] or 20 [msec]. Next, the out-of-step judging device 6b detects the current time t _K , ΔT time before t _K− 1,2Δ.
Internal voltage phase angle difference θ detected at time t _K-2 before T time
From (t _K ), θ (t _K-1 ), θ (t _K-2 ), the internal voltage phase angle difference at future time points τ ₁ , τ ₂ ... τ _P using the above equations (1) and (2). To calculate. Further, if the predicted value satisfies the expressions (3) and (4), it is determined that the step is out of step, and a control command is given to a system stabilizing device (not shown),
Step out of the generator can be prevented in advance. The third
The figure shows the operation of the above-mentioned step-out determination device 6 in a flow chart. As described above, by using the power system out-of-step predicting device of the present embodiment configuration, it becomes possible to early detect and detect out-of-step between the generators 1a, 1b, and thus using such a determination condition. By performing a predetermined system stabilization control by
System outage can be prevented in advance. In the above-described embodiment, the prediction calculation of the internal voltage phase angle difference at the future time is performed by the quadratic equation, but the same effect can be obtained by performing it by the Nth-order equation of the cubic equation or more. In this case, (N + 1) internal voltage phase angle differences up to the present time are required. [Effects of the Invention] As described above, according to the present invention, it is possible to prevent the out-of-step between the generators in advance by predicting and determining that the outage of the power system will occur. A high power system out-of-step predicting device can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a diagram for explaining a method of detecting an internal voltage phase angle difference between generators from an internal voltage sampling value. FIG. 3 is a flow chart for explaining the operation of the step-out determination device, FIG. 4 is a configuration diagram showing an example of the power system, and FIGS. 5 (a) to (d) are for steady state and step-out state. FIG. 6 is a diagram for explaining a temporal change of the internal voltage vector and the internal voltage phase angle difference, and FIG. 6 is a diagram for explaining a calculation method of the internal voltage phase angle difference and a step out determination method at a future time point. 1a, 1b …… Generator, 2a, 2b …… Voltage / current detector, 3a, 3b
…… Positive phase converter, 4a, 4b …… Internal voltage detector, 5a, 5b ……
Transmission system, 6 ... Step-out determination unit, 6a ... Internal phase angle difference detection unit, 6b ... Step-out determination unit.

   ────────────────────────────────────────────────── ─── Continuation of front page    (72) Inventor Kunio Matsuzawa               1-3 1-3 Uchisaiwaicho, Chiyoda-ku, Tokyo               Tokyo Electric Power Company (72) Inventor Ken Yanagibashi               1-3 1-3 Uchisaiwaicho, Chiyoda-ku, Tokyo               Tokyo Electric Power Company (72) Inventor Kazuya Omata               No. 1 Toshiba Town, Fuchu City, Tokyo Higashi Co., Ltd.               Inside the Shiba Fuchu factory (72) Inventor Masahiro Sato               No. 1 Toshiba Town, Fuchu City, Tokyo Higashi Co., Ltd.               Inside the Shiba Fuchu factory                (56) References JP-A-60-121916 (JP, A)                 JP-A-55-125925 (JP, A)                 JP-A-56-117540 (JP, A)                 JP 58-215916 (JP, A)

Claims (1)

(57) [Claims] A plurality of voltage / current detectors for respectively detecting the voltage and current at or near the terminals of the generators in the power system configured by linking a plurality of generators, and detected by the voltage / current detectors. A plurality of positive-phase converters that convert the voltage and current values of the generator into positive-phase values, and the internals of each generator based on the positive-phase voltage and positive-phase current of the generators converted by these positive-phase converters. A power system that includes a plurality of internal voltage detectors that detect voltage and a step-out determination unit that inputs the internal voltage of each generator detected by each internal voltage detector and predicts future out-of-step occurrence The out-of-step predictor according to claim 1, wherein the out-of-step determiner inputs the internal voltage of each generator from each of the internal voltage detectors transmitted via a transmission system to the internal voltage phase between the generators. An internal voltage phase angle difference detecting means for detecting the angular difference at a constant cycle Using the internal voltage phase angle differences at a plurality of past times detected by this internal voltage phase angle difference detection means, an approximate expression of a curve showing the relationship between the time and the internal voltage phase angle difference is obtained, and from this approximate expression Prediction calculation means for predicting calculation of internal voltage phase angle difference at each future time, and each predicted internal voltage phase angle difference calculated by this prediction calculation means shows a divergence tendency that increases with time, and its value Step-out prediction device for determining that step-out has occurred when it is determined that the value exceeds an allowable value.