JPS6277016A - Stepout predicting device for power system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a step-out prediction device that predicts a step-out in an electric power system in advance.

[Technical background of the invention and its problems] Bus voltages at multiple substations or power plants (two) are sampled at high speed, transmitted and received via a transmission system, and voltage phase angle differences are detected and The voltage phase angle difference is more than a certain value, for example 180
A method has been used in the past to detect a deviation in power and determine that it is a system out-of-step. However, system A voltage phase angle difference is detected without using the transmission system, and the future voltage phase angle difference is predicted and calculated based on the voltage phase angle difference at several points in the past, and system step-out can be detected early. The method has not yet been implemented.

If system out-of-step can be detected in advance (-child side), it becomes possible to perform various string stabilization Q3 controls from this condition C2 and prevent system out-of-step in advance. In order to prevent synchronization, it is absolutely necessary to detect synchronization in advance on the 1-child side rather than on the synchronization side.

[Aspects of the Invention H, Saw] The present invention detects a substation R [or a power plant (U) without using a bus line πi voltage phase angle difference transmission system at both ends of a power transmission line connected to the
It is an object of the present invention to provide a power system out-of-step adjustment device that predicts and calculates a future bus voltage phase angle difference based on the values at several points in the past.

[Summary of the Invention] The present invention measures the magnitude of the bus voltage VA on one side of a transmission line and the current vector i of that transmission line (the reference is the bus ■) at regular intervals, and calculates the bus voltage vector 9B on the other end. , detect the voltage phase angle difference θ between the two ends of the transmission line, and calculate the future voltage phase angle difference θ(1) from the voltage phase angle difference between C' and past kk points, and calculate its tendency and value. This allows for early detection of loss of synchronization.

"Embodiments of the Invention" First, the concept (principle) of detuning fill will be explained using an example of a power system with reference to FIG. 4 and subsequent figures.

Figure 4 shows an example of a power system. In the figure, l and 2 indicate a large power supply system consisting of a number of generator groups, and 3
indicates a large-capacity long-distance transmission line connecting large power supply systems 1 and 2.

Next, due to a system fault, etc., the busbar voltage at both ends of the long-distance transmission line 3? Man, ? The manner in which the B phase angle difference becomes 1B0 or more and systems M, I, and system 2 go out of synchronization will be explained by the movement of the bus voltage vector at both ends of the long-distance transmission line 3 and the movement of the voltage phase angle difference between the two. . In general, when a failure occurs in the power system C-system as shown in Fig. 1, the pressure phase angle This means that the difference is greater than a certain value, for example, 180 degrees or more), and system N] step-out occurs.Therefore, it is necessary to understand the movement of the bus voltage vector at both ends of the long-distance transmission line 3. Therefore, it is possible to detect the out-of-step phenomenon of system 1 and system 2.

Figure 5 (2) 0 person is the bus voltage of the connecting substation/Fi on the system 1 side of the long-distance transmission line 3 or the electric station such as a power plant, and 9B is the tangential substation or Represents the bus voltage vector of an electrical station such as a power station.

FIG. 5(a) shows a normal state in which the long-distance transmission line 3 is operated at an axis θa between the bus voltages VA and VB at both ends.

Next (1) Figure 5 (b) shows that due to system disturbances, etc., the power output of system 1 is different between the rear group and the generator group of system 2, and gradually (
Bus voltage at both ends of two long-distance transmission line 3? ,,? This shows how the phase angle difference between B and B increases. And Figure 5 (C)
indicates a case where the busbar voltage phase angle difference between both ends of the long-distance transmission line 3 increases and the angle exceeds a certain value, for example, 180 degrees C2. In such a state, system 1 and system 2 Loss of synchronization and goes out of step.

Furthermore, Fig. 5(d) shows the increasing tendency of the bus voltage phase angle difference at both ends of the long-distance transmission line 3 over time. In this case, the trend becomes monotonically divergent.

In this case (-1), when two large generator groups are interconnected via a long-distance transmission line and a system disturbance (2) occurs, the long-distance transmission is observed by observing changes in the bus voltage phase angle difference at both ends of the line. This allows us to detect out-of-step phenomena.

Next, a method of detecting the voltage phase angle difference between the busbars' at both ends of the long-distance power transmission line 3 will be explained.

The magnitude of the connected bus voltage on the system 1 side of long-distance transmission line 3 is ■
If the current vector of the long-distance transmission line 3 is i and the line impedance of the long-distance transmission line 3 is the line impedance of the long-distance transmission line 3 when Ayu vA is the reference phase, then the voltage vector of the connecting bus on the system 2 side of the long-distance transmission line 3 is ? B and its phase angle θ are expressed by equation (1) and (2)
I'm more sought after than this. Note that θ is a phase angle when seven people are used as a reference phase, and is equivalent to the bus voltage phase angle difference between both ends of the long-distance power transmission line 3.

Here, Re(QB) indicates the size of the real part of 9B, and Re(QB) indicates the imaginary part of 9B.

As described above, according to C-1, the angular difference θ of the main voltage potential 411 at both ends of the transmission line can be detected without using a transmission system.

Next, a method for predicting the bus voltage phase angle difference at a future point in time based on the bus voltage phase angle difference at several points in the past detected at intervals of ΔT will be described.

General (-1) After the faulty transmission line is cut off by the protective relay (2), the busbar voltage phase angle difference at both ends of the long-distance transmission line 3 changes discontinuously due to the large inertia of the generator groups of system Mk1 and system 2. Therefore, if you find a higher-order equation that passes the bus voltage phase angle differences at several points in the past, you can find the future bus voltage phase angle difference from that higher-order equation.

Hereinafter, step-out prediction when the higher-order equation is a quadratic equation (two equations will be explained using FIG. 3).

The bus voltage phase angle difference between both ends of the long-distance power transmission line 3 detected at intervals of ΔT is expressed as θ(tx), θ(tic-t)+θ(tK-2
), the curve tracing these three points is defined by equations (3) and (4).

θ(t)-〇(ty,-z) ten △θx2(t-tK-1
)+Δθols (t −tx−i) (t−tx−z
) (3) Here, tK is the current time, tK-1
indicates the time before ΔT, and tK-2 indicates the time before 2ΔT.

The bus voltage phase angle difference θ(τ) at future time τ is (3)
It is obtained by substituting τ for t in the equation.

Next, the step-out determination method C will be explained. The out-of-step judgment is (
3), Long-distance transmission line 3 at the future time determined by equation (4)
Whether or not the bus voltage phase angle difference between both ends of the bus shows a tendency to diverge and exceeds a preset boundary value (conducted from Y).
The bus voltage phase angle difference at future time τl<τ2<-----<τP is θ(τl)<σ(τ2)<・-<θ(τp)
(5) and θ(τp) >θI imit
In the case of (6) (determined as step-out), θItmit is the boundary value described earlier.

This step-out determination method is based on the following: When system 1 and system 2 step out, for example, at the -th wave, and the locus enters the long-distance transmission line 3 (=), the bus voltage phase angle difference at both ends becomes monotonous (-diverges and , utilizes the physical property of exceeding a certain boundary value.

An embodiment of the present invention will be explained in detail with reference to FIG.

11 is a connection bus bar on the system 1 side of the long-distance transmission line 3;
12 is the connection bus bar on the system 2 side. 13 inputs the secondary voltage of the voltage transformer FT connected to the bus line ζ2 and the secondary current of the current transformer CT installed on the transmission line (Y), samples these electrical quantities at a constant cycle, and outputs the A/D. This is a sampling device that converts and outputs the data.

14 is a voltage value for detecting the magnitude of the voltage of the connection bus 11 and the current vector i of the long distance transmission line 3 from the sampling values of the voltage of the connection bus 11 on the grid 1 side and the current of the long distance transmission line 3. This is a current vector detection device.

15 calculates the bus voltage phase angle difference at both ends of the long distance transmission line 3 from the voltage magnitude of the connection bus 11 and the current vector i of the long distance transmission line 3, and calculates the bus voltage phase angle difference at the past several points. This is a step-out detection device that predicts and calculates the bus voltage phase angle difference at a future point in time and detects step-out.

Note that the voltage/current vector detection device and the out-of-step detection device are implemented using, for example, the functions of a digital computer.

The operation of the invention will be explained below.

If a system disturbance such as a faulty transmission line occurs and the fault is removed from the protective relay (2), the intraocular pressure/current vector detecting device 14 will be activated as shown in FIG.
Voltage sampling value for one cycle of connection bus 11 on system 1 side output from 3 ■1. vz, ..., Vn-Lvn
Current sampling value during one period of long-distance transmission line 3
+ "L"'+ 'n-1, In is input, and the magnitude of the voltage of the connection bus 11 is calculated from the force formula, and the current vector i of the long-distance transmission line 3 is (8+, (9) , Q
Calculate from OJ formula.

In addition, the formula (8) is a formula for determining the thickness I of the current vector of the long-distance power transmission line 3, and the formula (9) is a formula for determining the phase ψ of the current vector when the voltage of the connection bus 11 is referenced. It is. Also, the QO) formula is a formula for determining the current vector i from I and ψ.

Here, Δξ is the time difference between the bus voltage sampling value of the connection bus 11 and the current sampling value of the long-distance transmission line 3 when they cross the zero point, as shown in FIG. 2 (:), and f is the frequency of the system. , the above calculation of vA,i is performed every cycle, that is, △
T=〒Performed every Cyu.

The step-out detection device 15 is connected to the seven people, i and the long distance power transmission line 3.
From the line impedance of
B is calculated, and then the phase angle θ of 9B is calculated using equation (2). Note that this phase angle θ is the phase angle of the connection bus 12 when seven people are used as a reference phase, and is equivalent to the bus voltage phase angle difference between both ends of the long-distance power transmission line 3.

Next, the operation of the step-out detection device 15 will be explained using FIG. 3. First, in step 811, the bus voltage phase angle difference θ(tX),
θ(tx-1).

Calculate θ(tK-2) and then (-step 82+Y) (3).

Using equation (4), future time points τl, τ2. ...τP(:
The bus voltage phase angle difference between the connecting buses 11 and 12 of the long-distance power transmission line 3 is predicted and calculated. Further, in step 88, it is determined whether or not the predicted value satisfies equations (5) and (6). If step S4 determines that step-out has occurred, a system stabilizing device (not shown) (control command Send (
Step 85). On the other hand, if it is not determined that the synchronization is out of synchronization, a constant delay is performed in step S6, and then steps Sl to S
Repeat the performance $1 judgment in step 4.

[Effects of the Invention] As described above, according to the present invention, for example, the bus voltage phase angle difference at both ends of the power transmission line is detected serially (two times), and the future bus voltage phase angle difference is predicted and calculated from the peaks of several past points. This makes it possible to detect synchronization at an early stage, and by performing system stabilization control using the determination criteria of such a device, synchronization can be prevented in advance. Further, in the present invention, the busbar electric phase angle difference at both ends of the power transmission line is detected without going through a transmission system, which is advantageous in terms of equipment compared to the prior art.

In addition, in the additional example of the present invention, the prediction calculation of the bus voltage phase angle difference at a future point in time is performed using a quadratic equation, but the same effect can be obtained even if it is performed using an N-order equation that is a cubic equation or higher.

However, in this case, (N+1) bus voltage phase angle differences up to the present time are required.

[Brief explanation of drawings]

Fig. 1 shows a structure M showing an embodiment of the present invention, and Fig. 2 shows a method for calculating the magnitude of the bus voltage and the vector value of the current from the sampled values of the bus voltage and current on one side of a long-distance transmission line. Diagrams for explanation; Figure 3 is a diagram showing the action of the step-out detection device; Figure 4 is a diagram showing an example of the power system; Figure 5 is a line drawing of the long-distance feed during steady state and step-out. FIG. 6 is a diagram for explaining temporal changes in the voltage vector and the bus voltage phase angle difference, and FIG. 6 is a diagram for explaining the method of calculating the bus voltage phase angle difference at a future point in time and the step-out determination method. 3...Power transmission line 11, 12...Bus bar 13
...Sampling device 14...Voltage/current vector detection device 15...Step-out detection device CT...Current transformer PT...Instrument transformer agent Patent attorney Nori Chika Yumu Contact person Meikasa same
Three Memin μ Figure 1 l V2 ・ ・ Figure 3 Figure 4 Figure 5 Figure U

Claims (1)

[Claims] The bus voltage and line current are sampled at a fixed period at any one of the multiple electric stations connected by the power transmission line, and the magnitude of the bus voltage and the current vector of the power transmission line at that electric station are detected. , from the magnitude of these bus voltages, the current vector, and the line impedance of the transmission line, find the bus voltage vector of another electrical station that faces the arbitrary electrical station, and from the real part and imaginary part of this bus voltage vector, calculate the voltage vector of both electrical stations. Obtain the bus voltage phase angle difference from time to time, calculate the future voltage phase angle difference from the voltage phase angle difference at multiple points, and lead to system step-out according to the value obtained by the calculation and the tendency of change. A power system out-of-step prediction device characterized by predicting in advance.