JPH0681423B2 - Power system stabilization method - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention determines whether or not a generator is out of step (stable determination) when one accident occurs in the power system, and makes the system unstable by control. The present invention relates to a system stabilization method for preventing the above.

[Conventional technology]

The basic equation of motion of a rotating machine such as a generator is generally expressed by the following equation.

MΔ = P _M −P _e where M: inertia constant, δ: phase difference angle (... is the second derivative),
P _M : Mechanical input, P _e : Electrical output.

Conventionally, the above equation is integrated twice to obtain the phase difference angle δ, and the motion state of the rotating machine is judged by the angle method comparing with the set value or by the energy method comparing both sides with δ and comparing with the energy amount. Was there.

Next, a conventional stability determination method will be described. Since the power / phase difference angle curve is often used to explain the stability determination of a rotating machine, it will be explained first. In Fig. 1 showing the characteristics of a rotating machine, 1 is the coordinate axis of the phase difference angle δ, 2 is the coordinate axis of the electrical output P _e , P _M is the initial mechanical input, and δ _s is the input / output balance at the initial stage (before the accident). When the phase difference angle increases, δ _c is the critical phase difference angle at which the rotating machine loses synchronization if the phase difference angle further increases, 6a ・
6b and 6c are loci with respect to the phase difference δ of the electrical input P _e , 6a shows the locus before the accident, 6b shows the accident, and 6c shows the locus after the accident is removed (the accident is removed by opening the accident line). . A is the area corresponding to the amount of kinetic energy that is accumulated in the rotating machine during the accident and tries to get the rotating machine out of synchronization, and B is the area corresponding to the amount of energy that the rotating machine can release after the accident is removed.

In the angle method, stability is determined by whether or not the phase difference angle δ = Δδ + δ ₀ (initial value) exceeds the critical phase angle δ _c by integrating the basic equation MΔ = P _M −P _e of the rotating machine twice. In this case, in order to obtain the initial value of the phase difference angle (which corresponds to δ _s because it is the value before the accident) that inevitably appears due to integration, it is necessary to determine the reference origin of the phase difference angle and the tidal current cross section. However, there were problems such as changes, and the reliability of that value was low.

However, δ ₀ is an initial value (= δ _s ).

In addition, to obtain the critical phase angle δ _c as the phase difference angle, the phase angle δ
It is extremely difficult for the same reason as _s, and values such as 180 ° are only given offline for convenience.

The energy method integrates both sides of the basic equation of the rotating machine MΔ = P _M −P _e , This is a method of comparing the two sides in the form of energy (hereinafter referred to as the formula (I)) in the form of energy and performing stability determination (in the dynamic model, an object of mass m is x ₁ to x ₂ due to an external force F). If the speed increases by Δ _v when moving to It can be understood that the formula (I) is a comparison of the amount of energy in comparison with this formula.

The left side of equation (I) is the kinetic energy stored in the accident (hereinafter referred to as E _K ) and corresponds to the area A.

However, t = 0 is the time when the accident occurs and t = tf is the time when the accident is removed.

The right side of the formula (I) is the amount of energy that can be released after the accident is removed and corresponds to the area B, and the stability determination is performed based on the size relationship between both sides (the size of the areas A and B).

By the way, according to the teaching of electric power engineering, there is a relation of P _e = α ・ sinδ, and α is a value determined by the configuration of the power system. It can be said to be an amount to represent. Therefore, the energy method can be rephrased as a method of performing stability determination by comparing the kinetic energy E _K stored during an accident and the proof stress (hereinafter referred to as potent energy E _c ) specific to the power system. Indeed in obtaining the potentiation dial energy E _c can be computed on the left side when the equality is satisfied in the stability and instability of the type sought criticality accident removal time t _c (I) in Shimiyureshiyon.

ω = Δω + ω ₀ , ω ₀ is the initial value of the angular velocity, and ω ₀ = 2π
Since it is determined that ₀ , ₀ = 50 Hz or 60 Hz, it is sufficient to consider only the deviation Δω. If calculated in this form, the phase angle δ _s and the critical phase angle δ _c , unlike the angle method, are not bothered, and the potential cross section E _c can be changed by changing the tide cross section.
The control amount can also be determined by putting out several stages. For example, the power flow cross section of all units → E _c → If this value causes instability, it is necessary to control one unit. (All units-1 unit) Power flow section of operation → E _c ′ → If it becomes unstable at this value, it is necessary to control another unit.

In this way, the energy method enables high-speed control because it is included in stability determination immediately after the kinetic energy is calculated, that is, immediately after the accident is removed. However, the proof capacity of the system after it is actually controlled and the system configuration has changed, and the potential energies E _c ′ and E _c ″ produced by the simulation in advance.
When the potential energy E _c of the actual system is not calculated online if it is not completely stabilized due to an error with the like, there is a drawback that the post-control by the energy method is not easy.

[Outline of Invention]

This invention uses the energy method capable of high-speed control in the first-stage control, and enables the post-additional control with the angular frequency for the post-additional control. The angular frequency ω appears during the stability determination calculation of the energy method. come Since it is a quantity calculated by, the number of measurement items does not increase, and there are many parts that can be shared with the energy method in the calculation process, so there is no need to create a separate control program, and stable determination is performed using different principles, It is an object of the present invention to provide a method for stabilizing a system that can be improved.

Example of Invention

An embodiment of the present invention will be described below with reference to the drawings. Second
In the figure, 9 is a power system, 10 is a generator unit to be stabilized, 11 is a transformer for measuring the instantaneous voltage, and 12 is a transformer.
Is a current transformer for measuring an instantaneous current, 13 is a power converter for converting each data from the transformer 11 and the current transformer 12 into an instantaneous power, and 14 is an arithmetic processing unit for determining stability and calculating a necessary control amount. , 15 is an output device that outputs a cutoff command, 16 is a circuit breaker that is opened by the cutoff command, 17 is a cable for transmitting data or a cutoff command (including a transmitting / receiving device when transmitting wirelessly) ). The energy method used for the first-stage control is the kinetic energy stored during an accident. And the potential energy E _c calculated by the simulation in advance is compared to determine the stability. First, as a concrete calculation method of the kinetic energy E _K , the instantaneous active power P _e is always measured online, and the level or the level V of the voltage V instantaneous active power (the voltage V for calculating P _e is naturally measured). there.) detecting the accident in, before the accident P _e
Level, that is, the difference between the initial mechanical input P _M and the instantaneous active power P _e that comes in every moment online is the time t at which the accident occurred.
From (= 0) to the accident removal time tf, the integration may be performed using the equation (1). Similar to the accident occurrence, the accident elimination shall be detected by the level of the instantaneous active power P _e or the voltage V. M is the total of the inertia constants of the controlled object, and the number of operating units is known from the instantaneous active power P _e level before the accident occurs, so the inertia constant of a single machine may be set in advance. In this way, the kinetic energy E _c is obtained at the time of eliminating the accident, so if the potential energy E _c is set in advance, the stability judgment can be started immediately.

Next, a concrete calculation method of the potential energy E _c will be described. Using the system to be controlled and the cross section of power flow, an accident is caused by simulation, the accident elimination time is changed, and the stability limit at which a step-out phenomenon occurs even if the accident is eliminated is obtained. If the accident elimination time t _c at that time is entered into the equation (1), the kinetic energy E _k = critical potential energy E _c at that time can be obtained. If the accident point is the point where the most severe step-out phenomenon occurs, the potential energy E _{c on the} safety side can be obtained. Next, when the power flow section is changed to 1 while all the power stations are stopped, 2 at all power stations, and so on, the potential energy E _c is _calculated by the above method, and the potentiometer corresponding to each power flow section is obtained. Energy E _c
(All units operated), E _c (all power plants stopped 1 unit), E _c (all power plants stopped 2 units), and so on, and the kinetic energy E _K calculated by equation (1) is the potential energy E _c The number of controlled vehicles can be determined depending on whether the level is exceeded.

Next, the follow-up control using the angular frequency ω will be described.

Therefore, if integration is started at the same time as the occurrence of an accident, and the first-stage control is determined to be stable, it is expected to complete immediately after that, and if it is determined to be unstable, the interruption will be completed considering the operating time of the auxiliary relay / circuit breaker. The transition of Δω is predicted by a method such as the least-squares method from the data of the points from the time. Then, if the sign of Δω is reversed, it is determined that the power system is stable (Fig. 3a) and unstable (Fig. 3b). This stability discrimination principle means that the kinetic energy before reaching the critical phase angle δ _c. Whether becomes 0, that is, Is passing through the 0 point and checking whether the sign is reversed,
It is easier to understand when compared with the dynamic model of FIG. Before passing through the critical phase angle δ _c , the operating energy becomes 0, and the sign of the velocity Δv of the object returning to the stable equilibrium point from 18 is
Equivalent to flipping to 19. In order to obtain the number of shutoffs, P _M , P _e , and M may be changed by the number of shutoffs so that the sign of Δω changes. In particular (Where n = number of operating units after initial stage control, m = required number of required control units, Z = impedance of transformer after initial stage control +
The line impedance to the system center, the impedance of the transformer after assuming that Z '= m units have been interrupted + the line impedance to the system center, and the interruption is performed by simulation. Is required. ) Is substituted into the equation (2) to obtain the required number m of control units whose sign of Δω is inverted. (If there is a cutoff in the first stage control, correct P _M and M in the same way before the follow-up control so that the electrical output
For P _e, use the measured value and continue the calculation according to equation (1). [Advantages of the Invention] As described above, according to the present invention, since the energy method is used for stable determination at the time of eliminating an accident, high-speed control is possible, and attention is paid to the angular frequency ω for follow-up control. Is also possible, Since the integral calculation is common to both controls, it is not necessary to increase the measurement items, and therefore the program can be shared, which leads to a reduction in the creation time, and the calculation processing time does not increase so much. Combining the principles has the effect of improving reliability.

[Brief description of drawings]

FIG. 1 is a power-versus-phase-angle curve diagram of a rotating machine, FIG. 2 is a block diagram of a system stabilizing device according to an embodiment of the present invention, and FIG.
FIG. 4 and FIG. 4 are operational characteristic diagrams of the system stabilizing device shown in FIG. 9 ... Power system, 10 ... Generator, 11 ... Transformer, 12 ... Current transformer,
13 ... Power converter, 14 ... Arithmetic processing device, 15 ... Output device, 16
… Circuit breaker, 17… Cable.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoshi Tsukuda 1-2-2 Wadazaki-cho, Hyogo-ku, Kobe-shi, Hyogo Mitsubishi Electric Corporation Control Works (72) Inventor Shuji Oshida Kazu, Hyogo-ku, Kobe-shi, Hyogo 1-2-1 Tasakicho Mitsubishi Electric Co., Ltd. Control Factory (72) Inventor Yasuhiko Terao 1-2-2 Wadazakicho, Hyogo-ku, Kobe Hyogo Prefecture Mitsubishi Electric Co., Ltd. Control Factory

Claims (1)

[Claims] 1. The deviation between the instantaneous active power and the initial mechanical input is integrated from the accident occurrence time to the accident elimination time, and the kinetic energy stored during the accident is calculated based on the angular frequency which is the integration result. If the kinetic energy is smaller than the potential energy, it is judged that the power system is stable, while if it is not small, it is judged that the power system is unstable, and the generator is shut off from the power system based on the kinetic energy and the potential energy. The first step and after the first step is completed, the transition of the angular frequency is predicted, and if the sign of the angular frequency is reversed, it is determined that the power system is stable, while the sign of the angular frequency is changed. If is not reversed, it is judged that the power system is unstable, and the generator of the power system is shut off as much as it is necessary to reverse the sign of the angular frequency. The second step and the power system stabilization method having the that.