JPH1014107A - Method of pulling systems into synchronism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cope with severe fault by repeating the open and make of a linking line one time or plural times after occurrence of fault when the fault of route break occurs in the linking line which links two systems. SOLUTION: In case that the systems A and B are linked with each other by one route and that the fault of rout break occurs in the linking line, the unbalance between demand and supply equivalent to the power blow PT of the linking line before accident occurs between the systems A and B due to the break of rout. As known from the direction power flow of before accident, in the system A, a group of generators accelerate and in the system B, they decelerate. So, at the point of time when the angle between both system opens and comes to 2π (360 deg.), the breaker is closed again, and then the off/on of the breaker are repeated with appropriate timing as occasion demands so as to discharge the energy accumulated in the system A to the system B, whereby both systems can be pulled into synchronism.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of synchronizing a system for synchronizing two systems connected via a connection line without interrupting the power supply when the two systems are separated.

[0002]

2. Description of the Related Art In general, when a fault occurs in a two-circuit transmission line, after a fault phase of the transmission line is cut off by a high-speed reclosing method, a predetermined no-voltage time (for example, 500 kV in a deionization time, for example, 500 kV). The fault was recovered by re-entering the accident phase after about one second in the above system).

[0003]

The re-closing condition according to the above-mentioned prior art must be a case in which each line is interconnected with two or more remaining phases other than the fault phase other than the accident phase, and furthermore, depending on the re-closing timing. However, there is a problem that a shock is also applied to the turbine shaft of the nearby generator.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and can cope with the most severe failure such as a route disconnection failure, thereby avoiding system separation and minimizing the influence on a generator turbine shaft. It is an object of the present invention to provide a synchronization pull-in method for a system that can be minimized.

[0005]

According to a first aspect of the present invention, there is provided a method for pulling a system in synchronization, wherein a route is routed to the interconnection line in which the two systems are interconnected via a single interconnection line. When a disconnection fault occurs, open the interconnecting line after the fault occurs,
The feeding is repeated at least once or more than once.
In this case, when the angle between the two systems is opened to reach 360 degrees, the interconnecting line is turned on again, and then the opening and closing of the circuit breaker is repeated at an appropriate timing, so that the energy stored in one system can be transferred to the other system. It can be released to the system and both systems can be pulled in synchronously.

[0006] According to a second aspect of the present invention, there is provided a method for pulling a system in synchronization according to the first aspect of the present invention.
The input was as follows, provided that the angle difference between the two systems was widened after the route was cut.

(1) Open during (2n-1) π <θ <2nπ 2 (π) <θ <(2n + 1) π, where θ is the angle difference n is an integer

According to a third aspect of the present invention, in the method for pulling in a system, in the first or second aspect, an electric station in a building is used instead of the two systems. In this way, even if the interconnection is released at the time of an accident in the interchange system between the buildings, the synchronization can be quickly pulled in.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram for explaining an interconnection system, in which a system A and a system B are interconnected by one route. The tidal current flowing between the respective systems is denoted by _PT , the arrows indicate the flowing direction, and the respective inertia centers are denoted by ∠θ ₁ and ∠θ ₂ .

First, consider a case where a route disconnection failure of the interconnection line has occurred. At this time, since the route is disconnected, a supply-demand imbalance corresponding to the interconnecting line power flow _PT before the accident occurs between the system A and the system B. As can be seen from the tide direction before the accident, the generator group accelerates in the system A and decelerates in the system B.

Therefore, in order to prevent such acceleration / deceleration, it is necessary to cut off the power supply. That is, the power supply is cut off in the system A, and the load is cut off in the system B. Here, if the route can be inserted immediately after the route break,
System A and system B should be able to be synchronized.

However, re-input immediately after the failure is not feasible in view of the necessity of one second of deionization time. Therefore, the angle between the two systems opens to 2π (360
°), when the circuit breaker is turned on again,
Turn ON / OFF circuit breaker at appropriate timing as needed
Is repeated to release the stored energy of the system A to the system B, both systems should be able to be pulled in synchronously.

FIG. 2 shows the movement of the phase angle and the emission
It is a relation diagram with stored energy. In FIG. 2, the vertical axis indicates the interconnection line power flow _PT , and the horizontal axis indicates the rotor phase angle difference θ of the generator group. In addition, P ₀ is the mechanical input, initially considered a constant. The operation of releasing the stored energy from the system A to the system B based on FIG. 2 will be described using the equal area method.

[0013] When the P _T and power flow, the energy of S ₀ + S _T is accumulated in the system A, the energy of S ₂ is released from the system A. Here, assuming that the inertia centers of the rotor phase angles of the generator groups of the respective systems A and B are θ ₁ and θ ₂ , these operation equations are expressed by equations (1) and (2).

[0014]

(Equation 2)

From equations (1) and (2), the relative motion of the center of inertia of systems A and B is expressed by equation (3).

(Equation 3) Equation (3) is equivalent to a generator equation of inertia constant M, mechanical input P ₀ , and electrical output _PT , and the transient stability can be discussed by the equal area method.

Now, ignoring the operation of the speed control means (GOV),
Assuming that the load has a constant power characteristic, the mechanical input P _{0 in} the above equation (3) has a constant value. Here, a case is considered in which the angle difference between the two systems is opened after the route is cut, and the circuit breaker is turned on again when the angle becomes 2π (360 degrees), and then the angle continues to be opened.

In this state, if the circuit breaker is operated as in equation (4), one off / on operation corresponds to S ₂ -S ₁ shown in FIG. Since the stored energy can be released to the system B, both systems can be drawn in synchronously. The OFF / ON repetition operation is performed when the angle difference is open, and the opening / closing timing is as shown in equation (4).

[0018]

(4) (2n-1) Open during π <θ <2nπ. Connected interconnection line during 2nπ <θ <(2n + 1) π .............. (4)

In order to perform these operations, it is necessary that S ₁ <S ₂ . If P _T = P sin θ holds, this condition can be expressed by equation (5).

P ₀ / P <1 / π (5)

[0020] However, because actually there is the influence of the governor means (GOV) and the load change, the value of P ₀ is slide into decline with time rather than at a constant. Further, the smaller the ratio of the interconnection flow to the equivalent inertia constant M is, the slower the acceleration between the two systems becomes. Therefore, the more the systems A and B become large-scale systems, the slower the switching timing becomes. Conversely, in the case of a single-machine infinite bus system (the system A is the target generator and the system B is the infinite bus), the control speed becomes the strictest in performing this control.

Next, the condition for terminating the open / close control will be described. After the angle difference between the systems A and B after the circuit breaker is turned from an increase to a decrease (that is, after both systems are pulled in synchronously), the circuit breaker is turned off / on according to the condition of equation (4). If the same is repeated as described above, the fluctuations are rather large, and it is necessary to end the control.

This will be described with reference to the drawings by the same area method as described above. First, at point A in FIG. 3, the angle difference between the systems A and B starts to decrease, and the state of the system moves in the lower left direction along the power curve. At this time, the above (4)
When the interconnecting line is opened at the point B according to the condition of the equation, the BC up to the point C where the stored energy stored in the system B is completely released.
The angle difference decreases along the arrow on the line, and the angle difference increases again.

On the other hand, if the interconnecting line is not opened at the point B, the power goes from A to B to D along the power curve, and the energy stored in the system B is released. As a result, the fluctuation is small. Become.

Next, the effect on the generator shaft torque will be described. Switching for synchronizing pull-in generates transient electromagnetic torque in the air gap of the generator as well as opening and closing of the circuit breaker, which may lead to shaft fatigue. In particular, when a circuit breaker is turned on, a large commercial frequency vibration torque is usually generated, and therefore, a check is required.

FIG. 4 shows a case where switching is performed at almost ideal timing (360 ° angle difference) (a).
And (b) the generator torque when switching is delayed by three cycles. The vertical axis indicates the generator torque [pu].
, And the horizontal axis represents time [seconds].

As can be seen from FIG. 4, in the former case (a), almost no transient vibration at the commercial frequency is observed, but when the switching is delayed (b), a large transient vibration torque appears. This is because, at ideal timing, the angle difference between the buses disappears and the generator output changes to 0, but if switching is delayed, the angle opens and the generator output changes on a step. It is thought that it is to try. Also, when the switching timing is too early, a similar transient vibration torque is generated.

50 Hz as shown in FIG.
When a vibration component is applied to the generator, a torsional force acts on the generator shaft, and as a result, a shock is applied. However, when the synchronization pull-in timing is adjusted, as shown in FIG. It was found that there was no shock to the generator.

FIG. 5 is a diagram showing the relationship between the switching timing shift and the transient vibration torque generated in the generator. In FIG. 5, the vertical axis indicates vibration torque [pu], and the horizontal axis indicates time [m].
s]. It can be seen from FIG. 5 that the transient vibration torque tends to increase in proportion to the switching timing shift.

According to the above-described embodiment, by repeating switching at least once or several times after disconnecting the route of the interconnection line, the separated systems can be synchronized quickly without any measures such as power cutoff and load cutoff. Can not only do
If the opening / closing timing of the breaker is ideal, the transient vibration of the electromagnetic torque of the generator is very small, and the influence on the wear of the shaft system is reduced.

The power system simulator test result of the synchronous pull-in switching shown in the above embodiment will be described below. For synchronization pull-in control by switching, a power system simulator test using one infinite bus system is performed to confirm its feasibility. At the same time, control logic verification and comparison with digital analysis will be conducted.

FIG. 6 is a model diagram of a simulator test model, and a test was performed using the model system diagram. First, the buses N ₂ ,
By detecting a phase voltage of N _4, it calculates the phase difference between the busbars,
Based on this, a circuit breaker switching signal is generated. The switching control block including the phase difference calculation and the like is created using a control system on a personal computer, and is created by a DSP (Digital).
This is realized by operating on a Signal Processor.

The phase difference was detected by detecting the phase difference θ = θ ₁ −θ ₂ between the buses N ₂ and N ₄ . In this case, V ₁ V
₂ × sin (θ ₁ −θ ₂ ) = V ₁ sin (ωt + θ ₁ ) × V
₂ cos (ωt + θ ₂ ) −V ₁ cos (ωt + θ ₁ ) × V ₂
Using the fact that sin (ωt + θ ₂ ), the signal V ₁ V
₂ × sin (θ ₁ −θ ₂ ) is calculated.

After the occurrence of the route disconnection fault, the phase difference θ ₁ −θ ₂
The breaker is turned on at the moment when increases and exceeds 360 degrees.
The phase difference is detected by creating these blocks using a computer and converting them into a DSP program. It should be noted that the DSP sampling time is 0.
5 ms.

FIG. 7 shows the test results. FIG. 7A is a diagram showing the internal state of the generator, and the vertical axis represents the generator active power [pu] and the generator angular velocity deviation (%). FIG.
(B) is the calculated value of V ₁ V ₂ sin (θ ₁ −θ ₂ ) by the DSP, and the vertical axis is the value [pu] of V ₁ V ₂ sin (θ)
, And the horizontal axis indicates time (s).

About one second after the elimination of the fault, the circuit breaker is turned on according to the control logic, and it can be seen that the system is kept stable without transient step-out. When the signal of V ₁ V ₂ × sin (θ ₁ −θ ₂ ) calculated by the DSP is seen, when the circuit breaker is turned on, the value is proportional to the generator active power output. It can be seen that the calculation is performed correctly.

At the moment when the phase difference reaches 360 degrees, it can be confirmed that the circuit breaker is closed. It can be seen that the generator output after turning on the circuit breaker contains almost no commercial frequency component, and almost no oscillatory transient electromagnetic torque is generated.
Therefore, the shock to the shaft system is small.

Next, the result of comparison with the result of digital analysis will be shown. EMT for the same system as the simulation test
An instantaneous digital simulation and an effective digital simulation using P (electromagnetic transient analysis program) were performed. The results are shown in FIGS. It can be seen that these all almost completely match the simulator test results of FIG.

According to the above simulation results, the following items (a), (b), and (c) were confirmed. (B) The feasibility of switching control and the validity of the control logic were confirmed by a simulator test. (B) The results of the analog simulator test almost coincided with the results of the instantaneous value digital simulation and the effective value digital simulation by EMTP, and it was clarified that examination using these analysis tools was possible. When it is not necessary to calculate the vibrating shaft torque, sufficient accuracy can be obtained by the effective value simulation. (C) If switching is performed at ideal timing,
The oscillatory transient electromagnetic torque generated in the generator is very small and has little effect on the shaft system.

According to the above embodiment, only the power transmission system has been described, but the present invention is not limited to this. That is, in recent cities, there is a local interchange system that has a power generation facility for each building unit and interconnects with adjacent buildings, but this method is also applied between these systems. it can.

In this case, the system A and the system B are simply replaced with an electric station (including a power generation facility or a single generator) in a building unit as it is.
Obviously, N may be as described in the above embodiment.

[0041]

As described above, according to the present invention, the stored energy between the systems is released by repeating the turning on and off of the circuit breaker a plurality of times in accordance with the predetermined phase difference after the disconnection of the interconnection line route. As a result, the phase difference between the respective systems is sequentially eliminated, and synchronization can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an interconnection system.

FIG. 2 is a diagram showing the relationship between the movement of the phase angle and the released / stored energy in the interconnection system.

FIG. 3 is a diagram illustrating an end condition of the opening / closing control.

FIG. 4 is a view for explaining a difference in transient vibration torque due to switching timing.

FIG. 5 is a diagram showing a relationship between a transient vibration torque that causes a shift in switching timing in a generator.

FIG. 6 is a model system diagram for a power system simulator.

FIG. 7 is a view showing test results of a simulator.

FIG. 8 is a diagram showing results of an instantaneous value digital simulator.

FIG. 9 is a diagram showing a result of an effective value digital simulation.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuyuki Tada 4-1 Egasaki-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture Inside the Electric Power Research Laboratory, Tokyo Electric Power Company (72) Inventor Hiroshi Okamoto E, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture 4-1, Kasaki-cho, Tokyo Electric Power Company, Electric Power Technology Research Institute (72) Inventor Takeshi Yamada 4-1, Egasaki-cho, Tsurumi-ku, Yokohama, Kanagawa Prefecture, Tokyo Electric Power Company, Electric Power Technology Research Institute (72) Inventor Kobayashi Naoki 4-1 Egasakicho, Tsurumi-ku, Yokohama-shi, Kanagawa Prefecture, Tokyo Electric Power Company

Claims (3)

[Claims] When a route disconnection fault occurs in two interconnected lines or one interconnected power plant and a system via a single interconnected line, a route disconnection fault occurs after the occurrence of the fault. A method of synchronizing a system, wherein opening and closing are repeated at least once or more than once. 2. The method according to claim 1, wherein the connection and disconnection of the interconnection line are performed as follows on condition that an angle difference between the two systems is opened after the route is disconnected. (1) Open during (2n-1) π <θ <2nπ 2 (π) <θ <(2n + 1) π, where θ is the angle difference n is an integer 3. The method according to claim 1, wherein an electric station in a building is used instead of the two systems.