JP2647085B2 - Step-out prediction device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to an out-of-step prediction device capable of predicting and determining out-of-step of a power system at an early stage.

(Prior art) Conventionally, as a means for detecting a step-out of a system due to a power system accident or the like, a voltage phase angle between electric stations at both ends of a transmission line of a power system is compared, and a difference between the two is determined. There is a method of detecting that the electrical angle has become, for example, 180 degrees or more and determining that the step-out occurs. However, such a means delays step-out detection, so that even if various system stabilization controls are performed under these conditions, there is a risk that step-out phenomena may spread to other parts due to a delay in control time.

(Problems to be Solved by the Invention) As described above, in the conventional method, it is not possible to early detect that the power system is out of step, and as a result, the out-of-step phenomenon spreads to other parts. There was a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a step-out prediction device that can early and highly accurately predict and determine that a power system will step out.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above-mentioned object, a step-out prediction device according to the present invention includes a plurality of generators in a power system including a plurality of generators. Power detection means for detecting the electrical output of each at predetermined time intervals, and, when an accident occurs in the power system, using the electrical output of each generator transmitted from the power detection means via the transmission means, respectively, The generator's angular velocity and internal phase angle are determined, and when the power system accident is removed, the kinetic energy and potential energy of the entire power system are calculated using the electrical output, angular velocity, and internal phase angle of each generator. Then, using the electrical output of each generator at a plurality of times from the accident removal to the present time, to find the coefficient of the preset estimation formula,
Next, using this estimation formula, an estimate of the electrical output of each generator is obtained, and then using this estimate, an estimate of the internal phase angle of the angular generator and each speed is obtained. Calculating means for obtaining a predicted value of kinetic energy and potential energy of the entire power system using the estimated values of the electrical output, angular velocity, and internal phase angle of the generator; and kinetic energy of the entire power system obtained by the calculating means Based on the predicted value of the kinetic energy and the predicted value of the potential energy on the basis of the predicted value of the potential energy and the predicted value of the potential energy, on the condition that the predicted value of the potential energy decreases and the difference between the two exceeds a predetermined threshold value. Step-out determination means for determining a key.

(Operation) In the step-out prediction device described above, when an accident occurs in the power system, the electric output of each generator in the system is detected by the power detection unit and transmitted to the calculation unit via the transmission unit. Then, in the calculating means, when the system fault is removed,
The kinetic energy and potential energy of the entire system are calculated based on the electrical output of each generator, and future values are predicted using the calculated values. Further, in the step-out determination means, the change tendency based on the kinetic energy and the potential energy of the entire power system predicted by the calculation means, that is, the predicted value of the kinetic energy increases, the predicted value of the potential energy decreases, and both Is detected as exceeding the preset threshold value, it is determined that the power system is out of synchronization.

Embodiment First, the concept of step-out determination according to the present invention will be described.

Methods for determining the out-of-step of the power system include a method using electrical information such as voltage and current, and a method using energy accumulated in the system due to a power system accident or the like. In particular, the latter is known as the energy method or the Lyapunov method. The out-of-step determination according to the present invention uses this energy method.

That is, equation (1) shows an example of the energy function.
In equation (1), the first term on the right side is the kinetic energy of the entire system, and the second term on the right side is the potential energy of the entire system.
The subscript i indicates each generator, and the subscript COI indicates various quantities of the center of inertia weighted by the inertia constant of the generator.

here, θ _i = δ _i −δ _CI (2c) P _ai = P _INi −P _ei … (2e) The symbols on the right side of the equations (2a) to (2f) mean the following, respectively.

M: inertia constant of the generator, ω: angular velocity of the generator, δ: internal phase angle of the generator, PIN: mechanical input to the generator, Pe: electrical output of the generator.

FIGS. 2 (a) and 2 (b) show examples of temporal movement of kinetic energy (hereinafter, referred to as KE) and potential energy (hereinafter, referred to as PE) when a three-phase short circuit accident or the like occurs in the power system. 2 (a) shows a case where the system is stable, and FIG. 2 (b) shows a case where the system is unstable (a part of the system loses synchronism). Now, as a feature of the Energy Law, it is known that the total energy obtained by adding KE and PE is constant. As can be seen from FIGS. 2 (a) and 2 (b), the energy accumulated by the system accident is After the accident has been eliminated, the KE and PE share each other. In a stable case, since the system absorbs the KE during the accident, the PE increases and the KE decreases. On the other hand, when unstable, the KE increases and becomes unstable because the system does not have the ability to absorb the KE during the accident. Therefore, by quickly catching such characteristics of the energy method by means of prediction, it is possible to make a quick and appropriate step-out determination. Specifically, the predicted values of KE and PE after the accident has been removed tend to change as shown in FIG. 2 (b), ie, KE increases, PE decreases, and the difference between the two is set in advance. When the threshold value is exceeded, it is determined that the system is out of synchronization.

Next, a specific calculation method of the energy value will be described.

First, in a steady state before the occurrence of the accident, the electrical output Pei (0) of each generator is detected, and the value is used as the mechanical input PINi of each generator. Next, if an accident occurs in the system, Δ
Using the electrical output Pei of each generator detected at t intervals,
The angular velocity ωi and the internal phase angle δi are calculated from the equations of motion shown in equations (3a) and (3b).

ω _{i (t)} = ω _i (t−Δt) + (P _INi− P _{ei (t)} ) Δt / M _i (3a) δ _{i (t)} = δ _i (t−Δt) + (ω _{i ( t)} + ω _i (t−Δ
t)) Δt / 2M _i (3b) Next, if the system fault is eliminated, the above-described angular velocity ω
i, using the calculation result of the internal phase angle δi, Calculating a _{P CI} from, KE than last (4) (t)
And PE (t) are obtained from the equation (5).

Next, a specific method of predicting the energy value will be described.

First, as shown in FIG. 3, using the actually measured values of the electric output Pei of each generator up to the present time, a coefficient of an estimated value set in advance by the least squares method is calculated. Then, the estimated value Pei ^* is obtained at intervals of Δt. For example, the case where the estimation expression is a quadratic expression represented by Expression (6) will be described.

First, the coefficients C ₁ , C ₂ , and C ₃ of the estimation formula are obtained by the least squares method using the actual measured values of the electric output Pei of each generator up to the present time. Next, the estimated time Pe is set for each Δt interval from equation (7), and is substituted into equation (6) to obtain the estimated value Pe.
Calculate i ^* .

t = t ₀ + n · Δt (7) (n = 1,..., ns) Here, t ₀ is the current time, and ns is the estimated number of times for each Δt interval.

Next, using the estimated value Pei ^* of the electrical output obtained at the Δt interval, in the same manner as the above-described calculation method of the energy value, the estimated value ωi of the angular velocity and the internal phase angle is obtained from the equations (3a) and (3b) ^* , Δi ^* are calculated. And Pei ^* , ωi ^* ,
Using δi ^* , a predicted value of kinetic energy KE ^* and a predicted value of potential energy PE ^* are obtained from equations (2), (4) and (5).

Finally, a method for determining out-of-step using the kinetic energy KE ^* and the potential energy PE ^* predicted by the above-described method will be described.

FIGS. 4 (a) and 4 (b) show KE and PE when it is determined that a step-out occurs.
FIG. 4 (a) shows the movement of the individual KE and PE, and FIG. 4 (b) shows the movement of the difference between them (KE-PE). I have. Also, in the figure, KE and PE indicate calculated values, and KE ^* and PE ^* indicate predicted values, respectively.

First, it is determined whether or not KE ^* and PE ^* are increasing and decreasing, respectively, by using equation (8).

As a result, if the individual motion of KE ^* and PE ^* satisfies the expression (8), the difference (KE ^* −PE ^* ) between the two at the final prediction time is set in advance by the expression (9). Threshold
It is determined whether or not El is exceeded. If these equations (8) and (9) are satisfied at the same time, it is finally determined that the step-out occurs.

The ^{KE * (to + ns · Δt} ) -PE * (to + ns · Δt)> E I ... (9) Note that FIG. 5 shows the overall flow diagram of the step-out determination method according to the present invention described above. As described above, according to the present invention, the motion of the entire power system, which is an index of whether or not a step-out phenomenon of the power system occurs based on the output (electrical output) of the generator before and after the occurrence of the accident in the power system, Energy and potential energy are calculated online, and the calculated value is used to predict a short-term future change, and the out-of-step phenomenon of the power system is determined at an early stage (determination of stability) from the change tendency. is there.

Hereinafter, an embodiment of the present invention based on the above-described concept will be described with reference to the drawings.

FIG. 1 shows a configuration example of a power system to which a step-out prediction device of the present invention is applied. In FIG. 1, reference numeral 1 denotes a target power system, G1 and G2 denote generators incorporated into the power system 1, and B1 and B2 denote buses on the generators G1 and G2 side. Meanwhile, 21,2
2 is a power detecting means for detecting the electrical output of each of the generators G1 and G2 via the instrumentation transformers PT1 and PT2 and the current transformers CT1 and CT2, respectively. Transmission means 4 for transmitting the detection signals respectively, and 4
2, each generator G1, G2 which is a detection signal transmitted through
Calculating means 5 for calculating and predicting the kinetic energy KE and the potential energy PE of the entire system based on the electrical output of the input, and 5 the kinetic energy KE and the potential energy of the entire system predicted by the The predicted value of kinetic energy KE increases based on PE and potential energy
This is a step-out determination means for determining that the system is out of step when the predicted value of the PE decreases and the difference between the two (KE-PE) exceeds a preset threshold value.

Next, the operation of the step-out prediction device configured as described above will be described.

First, in the steady state, the generators G1 and G2
The electrical output of is detected by the power detection means 21 and 22,
The data is transmitted to the calculation means 4 via the transmission means 31 and 32. Then, in the arithmetic means 4, this value is used as the mechanical input P of each generator G1, G2.
This is stored as INi (step S1 in FIG. 5).

Next, when an accident occurs in the power system 1 in such a state, the electric output Pei of the generators G1 and G2 is set in the same manner as in the steady state.
(T) is detected at intervals of Δt by the power detection units 21 and 22 and transmitted to the calculation unit 4 via the transmission units 31 and 32.
Then, in the arithmetic means 4, the transmitted generators G1, G
Using the electrical output Pei (t) of step 2 in step S2 of FIG.
Of each generator G1, G2, the internal phase angle ω
i is required.

Next, when the system fault is eliminated, step S3 in FIG.
The kinetic energy KE and the potential energy PE of the whole system are obtained by the action of. Further, when a certain period of time has elapsed after the removal of the system fault, the kinetic energy and the position are calculated according to the operations of steps S4 to S7 in FIG. The predicted values KE ^* and PE ^{* of the} energy are obtained. The out-of-step determining means 5 uses the predicted values KE ^* and PE ^* of the kinetic energy and the potential energy obtained by the calculating means 4 to obtain a fifth step.
The step-out determination of the power system 1 is performed by the operation of step S8 in the figure. As a result, when it is determined that a step-out occurs, a result of the determination is output to a system stabilization device (not shown), and system stabilization control is performed to prevent a step-out of the system in advance. If it is not determined that the step-out occurs, the fifth step
Returning to step S2 in the figure, the step-out determination described above is continuously performed for a certain period after the occurrence of the accident.

As described above, the step-out prediction device according to the present embodiment has two steps.
Detecting means 21 and 22 for respectively detecting the electrical output of each generator G1 and G2 in the power system 1 including the two generators G1 and G2, and transmitting means 31 from the power detecting means 21 and 22. , 3
The kinetic energy and potential energy of the entire system are calculated (KE, PE) and predicted (KE ^* , P) based on the electrical output of each generator G1, G2 transmitted via
E ^* ) calculating means 4, and the kinetic energy KE ^* and the potential energy PE of the entire system predicted by the calculating means 4
^* , The predicted value KE ^* of the kinetic energy increases, the predicted value PE ^{* of the} potential energy decreases, and the difference (KE
^* -PE ^*) since constructed and a determining step-out determination means 5 with step-out of the system on condition that exceeds a preset threshold value E _l, de-power system 1 by accident Can be detected at an early stage, and by performing some system stabilization control using the determination conditions of the out-of-step prediction device, it is possible to prevent the power system 1 from leading out of step in advance. can do. That is, in the step-out prediction device of the present embodiment, changes in kinetic energy and potential energy of the entire power system 1 are grasped online, so that energy changes corresponding to changes in the system state and changes in accident points can be captured. Therefore, the step-out phenomenon of the power system 1 can be determined early and with high accuracy.

In the above embodiment, for simplicity of description, the case where the number of generators incorporated into the power system 1 is two has been described. However, the present invention is not limited to this, and the present invention can be similarly applied to the case of three or more generators. Can be done.

[Effects of the Invention] As described above, according to the present invention, a power detection unit that detects an electrical output of each generator in a power system including a plurality of generators at predetermined time intervals, When an accident occurs in the power system, the angular velocity and internal phase angle of each generator are obtained by using the electrical output of each generator transmitted from the power detection means via the transmission means, and then the power system Is removed, the kinetic energy and potential energy of the entire power system are obtained using the electrical output, angular velocity, and internal phase angle of each generator, Using the electrical output of the generator, find the coefficient of the preset estimation formula, then use this estimation formula to find the estimated value of the electrical output of each generator position, and then use this estimated value Estimate the angular velocity and internal phase angle of each generator. Next, using the estimated values of the electrical output, angular velocity, and internal phase angle of each generator, calculating means for obtaining predicted values of kinetic energy and potential energy of the entire power system, and electric power obtained by the calculating means Based on the predicted values of the kinetic energy and the potential energy of the entire system, the condition is that the predicted value of the kinetic energy increases, the predicted value of the potential energy decreases, and the difference between the two exceeds a preset threshold value. Out-of-step determining means for determining out-of-step of the electric power system. Can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration example of a power system to which a step-out prediction device of the present invention is applied, and FIGS. 2 (a) and 2 (b) show temporal changes in energy when a three-phase short-circuit accident or the like occurs in the power system. FIG. 3 is a diagram showing a movement, FIG. 3 is a diagram for explaining a method of estimating an electric output of a future generator, and FIGS. 4 (a) and 4 (b) are temporal movements of energy when it is determined that a step-out occurs. FIG. 5 is a flowchart for explaining the overall flow of the step-out determination method. 1 ... power system, 21 and 22 ... power detection means, 31 and 32 ... transmission means, 4 ... calculation means 4, 5 ... step-out determination means.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Eiji Hioki 20-1 Kitasekiyama, Odaka-cho, Midori-ku, Nagoya-shi Within Chubu Electric Power Co., Inc. (72) Inventor Kazuya Omata Toshiba, Fuchu-shi, Tokyo No. 1 in the Toshiba Fuchu Plant Co., Ltd. (72) Inventor Masahiro Sato 1 in Toshiba-cho, Fuchu City, Tokyo Prefecture In the Toshiba Fuchu Plant Co., Ltd. (56) References JP-A-61-214726 (JP, A) Sho 61-214728 (JP, A)

Claims (1)

(57) [Claims] An out-of-step predicting device for predicting out-of-step of a power system including a plurality of generators, wherein power detecting means for detecting an electrical output of each of the generators at predetermined time intervals. When an accident occurs in the power system, using the electrical output of each of the generators respectively transmitted from the power detection means via the transmission means, to determine the angular velocity and internal phase angle of each of the generators, Next, when the accident of the power system is removed, using the electric output, angular velocity, and internal phase angle of each generator,
Determine the kinetic energy and potential energy of the entire power system, then use the electrical output of each of the generators at multiple times from the time after the accident was removed to the current time, to determine the coefficients of the preset estimation formula, and then Using an estimation formula, an estimated value of the electrical output of each of the generators is obtained, and then using this estimated value,
Obtain the estimated values of the angular velocity and the internal phase angle of each of the generators, and then use the estimated values of the electrical output, the angular velocity, and the internal phase angle of each of the generators to calculate the kinetic energy and the potential energy of the entire power system. Calculating means for calculating the predicted value of the kinetic energy and potential energy of the entire power system determined by the calculating means, the predicted value of the kinetic energy increases and the predicted value of the potential energy decreases. And a step-out judging means for judging that the electric power system has step-out on condition that a difference between the two exceeds a preset threshold value.