JPH0783553B2 - Power system fluctuation monitoring device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to relative angular velocity fluctuations and internal phase angles between generators when an accident occurs in a power system in which a plurality of generators are operated in parallel. The present invention relates to a power system motion monitoring device capable of monitoring motion.

[Technical background of the invention and its problems] In recent years, a plurality of power systems have become large-scaled, and various types of sway may occur depending on the type of accident, and some generators may be out of step. Furthermore, it is possible that the step-out phenomenon spreads to many generators and leads to a large-scale power outage. For this reason,
Various system stabilizers are applied to the power system.

On the other hand, the power system vibration monitoring device detects and monitors the relative angular velocity between generators and the time change of the internal phase angle after the occurrence of an accident, and introduces this monitoring result into the system stabilization device. As a result, extremely reliable stabilization control can be realized.

A conventional power system fluctuation monitoring device for introducing the monitoring result into the system stabilizing device will be described below.

Conventional power system oscillation monitoring devices target transient stability of about 1 second after the occurrence of an accident. In this case, the mechanical input to the generator output from the turbine governor system is almost constant. . Therefore, if the electrical output of each generator is measured, the angular velocity ω and the internal phase angle δ of each generator can be obtained from the generator operation equation as follows.

That is, first, a section (1, 2, ..., K, ...) At intervals of Δt seconds is determined from the time when the accident occurred. Here, Δt is about one cycle (16.7 to 20 milliseconds). Next, in each section K, the electrical output of the generator is sampled at a rate of r times,
If the values are Pk ₁ , Pk ₂ , ..., Pkr, the average value P of the section K
(Tk) is calculated by the equation (1). Note that tk is the time since the accident occurred and tk = KΔt.

P (tk) = (Pk ₁ + Pk ₂ + ... + Pkr) / r (1) Next, the change Δω (tk) of ω in the section K is (2)
If the mechanical input of the equation of operation is constant, it can be calculated from equation (3).

Mdω / dt = p _IN −P (tk)… (2) Δω (tk) = (P _IN −P (tk)) Δt / M… (3) where P _IN is the mechanical input to the generator. Yes, it will be almost constant for about 1 second after the accident, so the electrical output of the generator before the accident will be used. Further, M is the inertia of the generator.
Therefore, ω (tk) at the time of tk becomes the cumulative value of Δω (tk) ω (tk) = ω (tk-1) + Δω (tk) (4), and the internal phase angle δ (tk) also fluctuates. It can be calculated from equation (5).

δ (tk) = δ (tk- ₁ ) + (ω (tk) + ω (tk- ₁ )) Δt / 2 (5) Next, the relative angular velocity between generators ΔW, internal phase angle ΔD
Can be grasped by calculating the difference between ω and δ of each generator. For example, the relative angular velocity ΔWn, (n + ₁ ) (tk) and internal phase angle ΔDn, (n + ₁ ) (tk) between the nth generator and the (n + 1) th generation time are (6) and (7). ) Can be calculated respectively.

ΔWn, (n + ₁ ) (tk) = ωn (tk) −ω (n + ₁ ) (tk) (6) ΔDn, (n + ₁ ) (tk) = δn (tk) −δ (n + ₁ ) (tk) (7) FIG. 5 is a flow chart showing a method of calculating the relative angular velocity ΔW and the internal phase angle ΔD between the generators by the conventional fluctuation monitoring device for the electric power system described above. (For example,
"On-line high-speed stabilization method and algorithm based on grasp of power system fluctuation" (August, 1984) The Institute of Electrical Engineers of Japan, Poem B, p489) However, due to such a conventional fluctuation monitoring device, a power system accident When attempting to monitor relative angular velocity fluctuations or internal phase angular fluctuations during the power generation period of several seconds to 10 seconds after the occurrence, the mechanical input to the generator changes due to the response of the turbine governor system. The conventional device of constant input cannot be applied.

[Object of the Invention] The present invention has been made to solve the above problems, and an object of the present invention is to consider a change in mechanical input due to a reaction of a turbine speed governor system of a generator, and to prevent an accident in a power system. Several seconds after the occurrence
It is an object of the present invention to provide a power system fluctuation monitoring device capable of monitoring relative angular speed fluctuations and internal phase angle fluctuations between generators for about 10 seconds.

[Summary of the Invention] In order to achieve the above object, according to the present invention, in an electric power system in which a plurality of generators are operated in parallel, the electric power of each of the generators operated in parallel in the electric power system. Based on the electric power detection means for detecting the output and the electric output of each generator detected by this electric power detection means, a differential equation simulating the generator and a motion equation simulating the turbine governor system of the generator are calculated. Comprising a calculation means for calculating and outputting the angular velocity and internal phase angle of each of the generators by numerical integration, so as to monitor relative angular velocity fluctuations and internal phase angle fluctuations between the generators. It is characterized by having done.

First, the basic idea of the present invention will be described with respect to the method of calculating the angular velocity ω and the internal phase angle δ of each generator, and the method of grasping the relative angular velocity between generators and the internal phase angle.

That is, basically, by measuring the electrical output P of each generator and numerically integrating the equation of motion simulating the generator and the differential equation simulating the turbine governor system,
The angular velocity ω and the internal phase angle δ are calculated.

First, the equations of motion that simulate a generator are (8), (9)
It becomes an expression.

Where P _IN is the mechanical input to the generator from the turbine governor system, and M is the inertia of the generator.

Next, a differential equation that simulates the turbine speed governor system of the generator will be described.

FIG. 2 is a block diagram showing a turbine speed governor system of a general thermal power generator. That is, the turbine governor system inputs the angular velocity ω detected from the rotation speed of the generator shaft, and opens and closes the main steam valve to mechanically input P _IN from the high-pressure, medium-pressure, and low-pressure turbines to the generator. To control. Further, FIGS. 3 (a) to 3 (c) are examples of temporal changes in the electrical output P, angular velocity ω, and mechanical input P _IN of the generator when a three-phase ground fault or the like occurs in the power system. It is shown.

When an accident occurs in the power system, the electrical output P of the generator decreases and the angular velocity ω increases. Then, when the angular velocity ω increases, the mechanical input P _IN to the generator is suppressed by the response of the turbine governor system shown in FIG.

On the other hand, when the block diagram of the turbine governor system shown in FIG. 2 is converted into a differential equation, the following equations (10) to (18) are obtained.

x ₁ = −K ₁ ω + P _IN (O)… (10) x ₃ = K _H × x ₂ (15) x ₄ = K ₁ × y ₂ (16) x ₅ = K _L × y ₃ (17) P _IN = x ₃ + x ₄ + x ₅ ... (18) Therefore , Angular velocity ω and internal phase angle δ of each generator
Measures the electrical output P of each generator, and (8)-
It can be obtained by numerically integrating the differential equation shown in Eq. (18).

Next, taking the case of using the simplest Euler method as an integration method, the relative angular velocity fluctuation and internal phase angular fluctuation between generators are grasped from the electrical output of each generator before and after the accident. The method for doing so will be specifically described.

First, the electrical output of each generator before the occurrence of an accident is measured, and this is used as the initial value P _IN (O) of the mechanical input from the turbine speed control system to the generator.

When the occurrence of an accident in the electric power system is detected by the accident detection relay or the like, the electrical output of the generator is sampled and the average value P (tk) of the section K is obtained from the above equation (1).

Then, the fine coefficient Δf ₁ ~Δf ₅ of the differential equation of f ₁ ~f ₅ (19)
~ Obtained from equation (25).

Δf ₂ = ω ₀ ω (tk− ₁ ) (20) Δf ₃ = (x ₁ −y ₁ (tk− ₁ )) / T ₁ (21) where x ₁ = −K ₁ ω (tk− ₁ ) + P _IN (O)… (20) Δf ₄ = (x ₂ −y ₂ (tk− ₁ )) / T ₂ … (23) where, Δf ₅ = (y ₂ (tk− ₁ ) −y ₃ (tk− ₁ )) / T ₃ (25) Furthermore, the values of ω, δ and y _{1 to} y _{3 at} the time of tk are (26) to (3
Calculate from 0).

ω (tk) = ω (tk− ₁ ) + Δf ₁ × Δt… (26) δ (tk) = δ (tk− ₁ ) + Δf ₂ × Δt… (27) y ₁ (tk) = y ₁ (tk− _{1 ) + Δf 3 × Δt ... (} 28) y 2 (tk) = y 2 (tk- 1) + Δf 4 × Δt ... (29) y 3 (tk) = y 3 (tk- 1) + Δf 5 × Δt ... (30 ) Next, set the mechanical input P _IN (tk) at time tk to (31) to (32)
Calculate from the formula.

P _IN = K _H × x ₂ ＋ K ₁ × y ₂ (tk) ＋ K _L ＋ y ₃ (tk)… (31) where The method of calculating each speed ω and internal phase angle δ of each generator has been described above.

Finally, the relative angular velocity ΔW and the internal phase angle ΔD during the power generation period are obtained from equations (6) and (7), respectively.

FIG. 4 is a flow chart showing the calculation contents of the relative angular velocity ΔW and the internal phase angle ΔD between the generators according to the present invention described above.

[Embodiment of the Invention] An embodiment of the present invention based on the above concept will be described below with reference to the drawings.

FIG. 1 shows a configuration example of a power system fluctuation monitoring device according to the present invention. In FIG. 1, 1a and 1b are two generators operating in parallel in the power system, and 2a and 2b are cutoffs for paralleling or disconnecting the generators 1a and 1b in the power system. The vessels, BUSa, and BUSb indicate busbars.

On the other hand, 3a and 3b are voltage transformers PTa and PTb and current transformers CTa and CTb.
Based on the outputs V ₁ a, V ₁ b and I ₁ a, I ₁ b from the above, a power detection unit that detects the electrical output Pa, Pb of each of the above generators ₁ a, ₁ b at a high speed in a certain fixed cycle. , 4a, 4b are transmission systems for transmitting the electric outputs Pa, Pb of the respective generators 1a, 1b detected by the electric power detection units 3a, 3b to the arithmetic unit 5 in the center. The calculation unit 5 is based on the electric outputs Pa, Pb of the respective generators 1a, 1b transmitted via the transmission systems 4a, 4b, and the equation of motion for simulating the generators 1a, 1b and the generators 1a, 1b. By numerically integrating a differential equation simulating the turbine governor system of 1b, the angular velocities ωa, ωb and the internal phase angles δa, δb of the generators 1a, 1b are calculated, and the calculation results are not shown. It is configured to output to the system stabilizer.

Next, in the fluctuation monitoring device of the power system having such a configuration,
First, in a steady state before an accident occurs in the electric power system, the electric power detection units 3a, 3b detect the electric outputs Pa, Pb of the respective generators 1a, 1b, and the electric outputs Pa, Pb are transmitted through the transmission systems 4a, 4b to the center. It is transmitted to the calculation unit 5 located at. And in the calculation unit 5. The electric output Pa, Pb of each generator 1a, 1b detected above is determined by the respective generator 1
It is stored as the initial value P _IN (O) of the mechanical input of a and 1b.

On the other hand, when an accident in the power system in this state is detected by an accident detection relay (not shown),
The electric power detectors 3a and 3b are the electric outputs Pa and P of the generators 1a and 1b, respectively.
b is sampled at a high speed at a certain fixed period, and this is transmitted to the arithmetic unit 5 at the center via the transmission systems 4a and 4b. Then, in this arithmetic unit 5, step S _{3 in} FIG.
By performing an operation in accordance with a to S _8, seeking relative angular ΔW and internal phase angle ΔD between the generator 1a generator 1b, and inputs to the system stabilizing device (not shown) results. Then, the system stabilizing device stabilizes the power system by performing the stabilizing control based on the result input from the vibration monitoring device.

As described above, according to the power system fluctuation monitoring apparatus of the present embodiment, the relative angular velocity fluctuation and the internal phase angular fluctuation between the generators 1a and 1b for several seconds to several tens of seconds after the occurrence of the power system accident. Can be grasped, and by inputting the grasped result to the system stabilizing device, extremely highly precise system stabilizing control can be realized.

In the above embodiment, the simplest Euler method was used as the integration method for solving the equation of motion of each generator and the differential equation of the turbine speed governor system, but it is not limited to this and other integration methods such as a trapezoidal integration method are used. It is needless to say that even if is used, the same effect can be obtained by carrying out similarly.

Further, although the above embodiment has described the case where the number of generators that are operated in parallel is two, the present invention can be similarly applied to the case where the number of generators is not limited to this and is three or more. Is.

In addition, the present invention can be variously modified and implemented within the scope of the invention.

[Effects of the Invention] As described above, according to the present invention, in consideration of the change in the mechanical input due to the reaction of the turbine speed governor system of the generator, the generator for several seconds to about 10 seconds after the occurrence of the power system accident. A fluctuation monitoring device for a power system capable of monitoring relative angular velocity fluctuations and internal phase angular fluctuations can be provided.

[Brief description of drawings]

1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a turbine governor system, and FIG. 3 (a).
~ (C) is a diagram showing an example of temporal changes in the electrical output, angular velocity, and mechanical input of the generator when an accident occurs in the power system, and Fig. 4 is a relative diagram between the generators according to the present invention. FIG. 5 is a flow chart showing the calculation contents of the angular velocity and the internal phase angle, and FIG. 5 is a flowchart showing the calculation method of the relative angular velocity between the generators and the internal phase angle by the conventional power system fluctuation monitoring device. 1a, 1b ... Generator, 2a, 2b ... Breaker, 3a, 3b ... Power detection part, 4a, 4b ... Transmission system, 5 ... Computing part.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hitoshi Otsuka 1-3-3 Uchisaiwai-cho, Chiyoda-ku, Tokyo Tokyo Electric Power Co., Inc. (72) Ken Ken Yanagibashi 1-3-1 Uchiyuki-cho, Chiyoda-ku, Tokyo East Within Kyodensha Co., Ltd. (72) Inventor Kazuya Omata No. 1 in Toshiba Fuchu, Tokyo Fuchu-shi, Tokyo Inside the Fuchu factory, Toshiba (72) Inventor Masahiro Sato No. 1 in Toshiba Fuchu, Tokyo, Fuchu factory (56) ) References JP-A-56-117540 (JP, A)

Claims (1)

[Claims] 1. In a power system in which a plurality of generators are operated in parallel, power detection means for detecting the electrical output of each of the generators operated in parallel in the power system,
Based on the electrical output of each generator detected by the power detecting means, numerical equations of a motion equation simulating the generator and a differential equation simulating the turbine speed governor system of the generator are numerically integrated to generate the respective power. And a calculation means for calculating and outputting the angular velocity and the internal phase angle of the electric machine, and the relative angular velocity fluctuation and the internal phase angular fluctuation between the generators are monitored. Vibration monitoring device.