JP2505403B2 - System stabilization method - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for stabilizing an electric power system, and in particular, uses an energy function to maintain synchronization between generators even after an accident occurs in the electric power system. The present invention relates to a system stabilization method by the model reference method.

[Conventional technology]

Conventionally, as a method using this kind of energy function, there is one shown in FIG. In Fig. 1, G1 is an accelerating generator group, G2 is a decelerating generator group (pumped-storage generator, generators with heavy loads close to each other), and the inertia constant, mechanical input value, and electric output value of each are And the respective back angles are δ ₁ and δ ₂ .
1 is a central processing unit (hereinafter abbreviated as CPU), A is a generator group G
1 shows the information sent to CPU1, B is C from generator group G2
It shows the information sent to PU1.

Next, the operation will be described. Information on generator groups G1 and G2 A and B
Are sent to the CPU 1 via the measurement and transmission devices T ₁ and T ₂ , respectively.

Then, the CPU 1 uses these pieces of information A and B to determine the kinetic energy E _K and the critical energy E _C during the accident.

Where _i is the equation of motion of the generator Than, Can be calculated by However, tf is the accident duration.

If the integral part of the above equation is numerically calculated using data sampled at a constant interval Δt, then _i
Is as follows.

Here, n = tf / Δt, ΔP _ij = P _mij −P _eij , and the subscript j represents certain sample data.

However, The subscript s represents a stable equilibrium point, and the subscript u represents an unstable equilibrium point.
E _C is a preset value.

The CPU 1 compares the kinetic energy E _K with the critical energy E _C and makes a stability determination by the following equation.

E _K ≤ E _C → stable E _K ＞ E _C → unstable If it is determined to be unstable, kinetic energy E _K ′, critical energy assuming a partial cutoff of the generator group G2 on the deceleration side
Calculate E _C ′.

Then, the smallest assumed cutoff amount that satisfies E _K ′ ≦ E _C ′ is determined as the stabilization control amount, and the system is stabilized by actually cutting off part of G2 corresponding to that amount. .

The conventional system stabilization method using the energy function is configured as described above, and since the critical energy is set assuming the severest accident condition and power flow condition, the accident point and power flow condition can be preset. If they are different, there is a drawback that the control error becomes large and there is a tendency for excessive shutoff.

[Outline of Invention]

This invention has been made to eliminate the above-mentioned drawbacks of the conventional ones. Based on the model reference method, the critical energy (potential energy at the unstable equilibrium point) is automatically calculated by information after clearing the accident. It is intended to provide a system stabilization method that can improve the cutoff accuracy by calculation.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. In the two-machine system as shown in FIG. 1, the kinetic energy E _K is expressed by using the energy function method as shown in the equation (1). When Σ of the equation (1) is expanded, the kinetic energy E _K is as follows. become that way.

Further, the critical energy E _{C at} the unstable equilibrium point can be expressed by using the equation (3), but if the equation (3) is modified, the critical energy E _C becomes as follows.

here, So Therefore, Where (P _e1 -P _m1 ) and (P _e2 -P _m2 ) (δ ₁ −δ ₂ )
Assuming the change due to Focusing on these equations (4) and (5), both (M ₁ · M ₂ ) /
There is a term of (M ₁ + M ₂ ). Since the system stability determination is performed by comparing E _k and E _c , Can be determined by. this is, By replacing with, it can be expressed as stability judgment of a single-machine infinite bus system. This virtual one-machine infinite bus system is shown in the equivalent circuit diagram of FIG. However, X in the figure is a transfer reactance. In this way, focusing on the fact that the two-machine system of FIG. 1 is virtually represented by a one-machine infinite bus system, the model reference method uses the transient stability of the one-machine infinite bus system of FIG. Can be explained by the characteristic diagram of the power phase difference angle curve shown in FIG. Now, let X1 be the transfer reactance after clearing an accident in a system with a certain reference, and the corresponding critical energy E _c 1 at the unstable equilibrium point
Has a value equal to the area (aijfa) in FIG. This reference system can be selected arbitrarily and E _c 1 can be set in advance. On the other hand, when the transfer reactance of the system subject to stability determination after the accident is cleared is X2, the critical potential E _c 2 at this unstable equilibrium point corresponds to the area (bgheb) in FIG. However, this value is
It is unknown until the electrical output Pe of 1, G2 passes through the unstable equilibrium point (point e in Fig. 3). Therefore, the measurement of this electric output Pe is stopped at a certain point (for example, h point), and the critical energy
Predict and calculate E _c (2). That is, since E _c (1) = area (aijfa) E _c (2) = area (bgheb), Holds.

Assuming that Get. This equation (9) is defined by the set amount E _c (1) and the area (cijd
c) and the measured area (cdhdc).
However, this assumption holds better as the h-point is closer to the e-point, but Pe is too close to the e-point (unstable equilibrium point).
When you measure, the stabilization control will not be in time, so actually use the data up to the h point to predict the subsequent Pe,
Guarantees control accuracy and responsiveness. In this way, the predictive calculation of E _c (2) is performed based on the information after clearing the accident, and the accuracy of the system stability determination and control amount is improved.

Although the power phase difference curve is used for calculating E _c (2) in the above embodiment, since the actual control is performed in a time sequence, a reference is given to the area on the time-electrical output plane. You can also Furthermore, the equivalent 2
This method can be applied to a multi-machine system that can be expressed as a collection of machines.

[Effects of the Invention] As described above, according to the present invention, the cutoff ratio of the generator group that decelerate is calculated based on the information after clearing the accident based on the model reference method. Even if the power flow condition is different from the set condition, highly accurate stability determination and control amount determination can be performed.

[Brief description of drawings]

Fig. 1 is a block diagram of the system stabilizer, Fig. 2 is an equivalent circuit diagram of a virtual one-machine infinite bus system that represents the two-machine system equivalently, and Fig. 3 is the power of the power system shown in Fig. 2. It is a characteristic view which shows a phase difference angle curve. 1 ... Central processing unit (CPU), G1, G2 ... Generator group, T ₁ , T
₂ …… Measuring and transmitting equipment. X ... Transfer reactance, Vg ... Generator back voltage, ...
… Power phase difference angle curve before accident ………… Power phase difference angle curve after accident removal that becomes a reference ………… Power phase difference angle curve after actual accident removal ………… Power phase difference angle curve during accident

 ─────────────────────────────────────────────────── (72) Inventor Kunio Matsuzawa 1-3-3 Uchisaiwaicho, Chiyoda-ku, Tokyo Tokyo Electric Power Company, Inc. (72) Inventor Hitoshi Otsuka 1-3-1 Uchiyuki-cho, Chiyoda-ku, Tokyo TEPCO (72) Inventor Tadahiro Goda 1-2-2 Wadazaki-cho, Hyogo-ku, Kobe Mitsubishi Electric Corporation Control Works (72) Inventor Shuji Oshida 1-2-1 Wadazaki-cho, Hyogo-ku, Kobe Mitsubishi Electric Co., Ltd. Control Works (72) Inventor Shogo Nishida 1-2-1 Wadazakicho, Hyogo-ku, Kobe City Mitsubishi Electric Co., Ltd. Control Works

Claims (1)

(57) [Claims] 1. A system for interrupting the generator group that decelerates in the event of an accident in a power system interconnecting the accelerating generator group and the decelerating generator group to maintain synchronization between the generator groups. In the stabilization method, the amount of change in active power during an accident is calculated to obtain the stored energy value during an accident for the predetermined interruption ratio, and the electrical output after the accident is eliminated is integrated for a certain period of time, resulting in instability. A system stabilization method, comprising predicting critical energy at an equilibrium point, comparing the stored energy value and the critical energy, and determining a cutoff ratio of the generator group that is decelerating.