JPH0477536B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a system stabilization method for preventing synchronization between generators after an accident occurs in a power system, causing the power system to become unstable and collapse. It is related to.

Conventionally, this type of method has been shown in FIG. In this figure, 1 is the power system, A
indicates an accident detection terminal, B indicates a power plant to be controlled, 10 indicates a central processing unit (hereinafter referred to as CPU 10), and an accident signal AS is sent from accident detection terminal A to CPU 10, and
Shutdown command from CPU10 to power plant B to be controlled
BS is sent. Furthermore, 11 is a verification circuit.

Next, the operation will be explained. The accident detection terminal A detects the type of accident based on the operation signal of the protection relay and sends the accident signal AS to the CPU 10. On the other hand, in the CPU 10, the comparison circuit ₁₁ performs a comparison with the fault current value K ₁ and _the predetermined fault conditions
Or it determines whether it is necessary to cut off BG ₂ , and if necessary, issues a command to control power plant B to cut it off.

Conventional system stabilization methods are configured as described above, so as the number of fault detection terminals A increases, the amount of information to be transmitted becomes extremely large, and it becomes difficult to determine the conditions to be set. Furthermore, when an accident occurs within the same power transmission line, the fault points cannot be distinguished from each other, so the amount of damage will vary depending on the fault point within the same power transmission line, and it is extremely difficult to accurately distinguish or judge this. It was difficult.

This invention was made in order to eliminate the drawbacks of the conventional ones as described above. To provide a system stabilization method that can accurately determine the stability of the energy method and calculate the necessity and cutoff amount according to the energy method by accurately determining the kinetic energy during the accident using electrical output value data during the accident, etc. It is an object.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In Figure 2, G ₁ is a group of generators that accelerate due to a short circuit or ground fault that occurs in the power system, and G ₂
is the generator group (including pumped storage generators) that slows down due to the accident, and _G3 is the generator group that does not accelerate or decelerate due to the accident, and the inertia constant when each is equivalently aggregated into one machine. electrical input value, electrical output value
M ₁ , P _M1 , P _e1 ; M ₂ , P _M2 , P _e2 ; M ₃ , P _M3 ,
P _e3 ; Furthermore, let the phase angles of the back voltage of the transient reactance be δ ₁ , δ ₂ , and δ ₃ , respectively.

Further, the CPU 20 is a central processing unit (hereinafter referred to as CPU 20) that implements the stabilization method according to the present invention.
, TS ₁ , TS ₂ , and TS ₃ indicate the respective information. Information TS ₁ is the information sent to the CPU 20 from the accelerating generator G ₁ , and information TS ₂ is the information sent from the decelerating generator G _2.
The information TS 3 indicates the information sent to the CPU 20, and the information TS ₃ indicates the information sent to the CPU 20 from the generator G ₃ that does not accelerate or decelerate. Specifically, information TS ₁
is the inertia constant M ₁ , mechanical input P _M1 , electrical output P _e1 ,
Information TS ₂ similarly represents the inertia constant M ₂ , mechanical input P _M2 , and electric power output P _e2 , and information TS ₃ represents the inertia constant M ₃ .

Using this information, the CPU 20 executes a stabilization control algorithm based on the energy method and according to the flowchart in FIG. 3.

In FIG. 3, 31 is a startup block that starts the algorithm on the condition that an accident has occurred in the system, 32 is a processing block for calculating the total kinetic energy K _M accumulated in each generator during the accident, 33 corrects the preset critical energy E _C from online data of the generator electrical output after clearing the accident, and calculates this correction value.
34 is a judgment block that compares the magnitude of K _M and E _C2 ; 35 _is a processing block that judges that it is stable when K _M < E _C2 and moves to algorithm stop block 36; 36 is K A processing block that determines instability when _M ≧E _CB and moves to a stabilization control amount (partial cutoff amount of the deceleration generator) determination routine; 38 is a processing block that selects the minimum shear cutoff ratio K , 39 are the kinetic energy K _M and the corrected critical energy E _C2 assuming a K-minute shear break.
Processing block for calculating 3a is K _M and E _C2
Judgment block that compares the size of , 36 is K _M < E _C2
3d is a processing block that judges that stabilization can be achieved with K-minute shear and breakage, outputs a break-off signal for that amount, and moves to algorithm stop block 3c, 3d is K _M
If ≧E _C2 , it is determined that the shearing and shearing amount for K is insufficient, the next highest shedding ratio is selected, this is newly set as K, and the processing block returns to processing block 39.

Next, a method of calculating operating energy using online data will be explained with reference to FIGS. 4 and 5. Hereinafter, subscript 1 indicates various quantities related to the equivalent generator obtained by consolidating accelerator generator G1 into one unit using the short-circuit capacity method, subscript 2 indicates the equivalent aggregated generator quantities of deceleration generator G2, and subscript 3 indicates the same quantities. Equivalent aggregated generator quantities of generator group G3 without acceleration/deceleration are shown. In addition, these equivalent generators are newly expressed as G ₁ , G ₂ , and G ₃ .

In Fig. 2, if internal losses of each generator G ₁ , G ₂ , G ₃ are omitted, the equation of motion of a normal generator is M _i δ¨ _i =P _Mi −P _ei (i=1 to 3)... …(1) becomes.

Here, δ ₀ = (M ₁ δ ₁ + M ₂ δ ₂ + M ₃ δ ₃ ) / (M ₁ + M ₂ + M ₃ ) ...(2) θ _i = δ _i −δ ₀ ......(3), and all To find the kinetic energy K _M accumulated in the generator during a system accident, K _M = 1/2M ₁ θ〓 ₁ ² + 1/2M ₂ θ〓 ₂ ² + 1/2M ₃ θ〓 ₃ ²
...(4) =1/2M ₁ δ〓 ₁ ² +1/2M ₂ δ〓 ₂ ² +1/2M ₃ δ〓 ₃ ² -1/2 (M ₁ +M ₂ +M ₃ ) δ〓 ₀ ² ......(5 ) becomes. By replacing equation (3), the power system out-of-step phenomenon is determined by the relative relationship between the phase angles of the voltage behind the transient reactance of the generator, so each deviation from the average value _δ weighted by the inertia constant is It expresses the phase angle of the voltage behind the transient reactance of the equivalent generator.

Therefore, if the accident duration time is t _f , then from equation (1), δ〓 _i =∫ ^tf / ₀ ΔP _i dt/M _i (ΔP _i = P _Mi − P _ei ) ...(6). In this method, the integration of equation (6) is sampled at regular intervals and is executed using online data (ΔP _i ) _j of ΔP _i according to the following equation.

On the other hand, for the generator G ₃ without acceleration/deceleration, P _M3 −P _e3 = 0 ... (8), so δ ₃ = 0, and combining with equation (7), (5)
Substituting into the expression becomes. Therefore _{, as mentioned earlier} ^, _{if we} ^set Equation (9) is K _M = 1/2 {(M ₁ −M ₁ ² /M ₁ +M ₂ +M ₃ )(P _M1 /M ₁ ) ² X ²
−2M ₁・M ₂ /M ₁ +M ₂ +M ₃ (P _M1 /M ₁ ) (P _M2 /M ₂ )XY +(M ₂ −M ₂ ² /M ₁ +M ₂ +M ₃ )(P _M2 /M ₂ ) ² Y ² }……(12
) Next, we will explain the potential energy at the unstable equilibrium point after the fault is removed.

The potential energy E _C at the unstable equilibrium point is
As shown in Figure 4, it is sufficient to consider a two-machine model with an accelerating generator G ₁ and a decelerating generator G ₂ .
Calculate the respective electrical outputs P _e1 and P _e2 using the following formulas.

That is, P _e1 = G ₁₁ V ₁ ² + GV ₁ V ₂ cos (δ _{1 −} δ ₂ ) + BV ₁ V ₂ sin (δ ₁ − δ ₂ ) ……(13) P _e2 = G ₂₂ V ₂ ² + GV ₁ V ₂ cos (δ ₂ − δ ₁ ) + BV ₁ V ₂ sin (δ ₂ − δ ₁ ) ...(14) In equations (13) and (14), G ₁₁ , G ₂₂ and V ₁ , V ₂ are assumed to be constant. Then, if G, B, and δ (=δ ₁ −δ ₂ ) are determined, each electric output P _e1 , P _e2 is determined, and the system state can be estimated.

Also, the stable equilibrium point δ ₀ of this system is given by the equation of motion
From (1), calculate P _M1 −P _e1 /M ₁ =P _M2 −P _e2 /M ₂ by solving (15). Based on the stable equilibrium point δ ₀ found by this equation (15), the unstable equilibrium point δ _C is δ _C =
(π−δ ₀ ). Therefore, the potential energy E _C of the unstable equilibrium point δ _C can be obtained from the following formula.

E _C = ₂ 〓 ⁱ⁼¹ ∫〓 ^s 〓 ₀ (P _Mi −P _ei ) dδ ……(16) Potential energy obtained by equation (16)
Since E _C is calculated assuming the output value P _e , there is a difference from the output value P _e of the actual system, which causes an error in the potential energy E _C. FIG. 5 is a characteristic diagram of angle versus electrical output value showing the cause of this error. Curve a in Fig. 5 shows the relationship between the phase angle δ of the transient reactance back voltage of the generator in a healthy system and the electrical output P _e , and curve b in Fig. 5 shows the same relationship assumed after the fault has been removed. Curve c in FIG. 5 shows the relationship between the phase angle δ of the voltage behind the transient reactance and the electrical output P _e in an actual system. This shows the error between the actual system and the accident system assumed as the most severe condition, and the difference factor Δδ in potential energy between the actual system and the assumed system is the error factor in potential energy E _C. Therefore, in order to eliminate this error, by measuring the electrical output P _e after the fault has been removed, the potential energy E _C2 is newly calculated using the following formula.

E _C2 = E _C ×P _M −P _e* /P _M −P _e** ...(17) However, here, P _e* is the assumed active power after the fault is removed, and P _e** is the estimated active power after the fault is removed. is the measured active power.

By comparing the potential energy E _C and the kinetic energy K _M at the unstable equilibrium point obtained above, it is possible to predict whether a step-out phenomenon will occur.
That is, it is clear that the following relationship exists.

K _M > E _C → Unstable K _M E _C → Stable ...(18) Next, the stabilization control amount when it is determined to be unstable in equation (18), that is, the part of the reduction generator group. We will explain how to determine the

If this shearing ratio is K, then the inertia constant M ₂ of the reduction generator group is considered to have changed to M _a2 = (1-k) M ₂ ... (19), so δ ₀ in equation (2) is δ ₀ =M ₁ δ ₁ +M _a2 δ ₂ +M ₃ δ ₃ /M ₁ +M _a2 +M ₃ ) ...(20), and the kinetic energy of equation (5) is K _M1 = 1/2M ₁ δ〓 ₁ ² +1/2M _a2 δ〓 ₂ ² +1/2M ₃ δ〓 ₃ ² -1/2 (M ₁ +M ₂ '+M ₃ ) δ〓 ₀₁ ² ... (21). However, equations (6) and (7) remain unchanged.

Therefore, when formula (21) is expressed by X and Y in formulas (10) and (11), K _M1 = (M ₁ − _{M 1} ² /M ₁ +M _a2 +M ₃ )(P _M1 /M ₁ ) ²・X ² −2M ₁
M _a2 /M ₁ +M _a2 +M ₃ (P _M1 /M ₁ ) (P _M2 /M ₂ )XY + (M _a2 −M _a2 /M ₁ +M _a2 +M ₃ )(P _M2 /M _a2 )Y ² ... (2
2), and let E _C (k) be the potential energy at the unstable equilibrium point after a partial shear failure of the reduction generator group, then K _M1 E _C (k) is the smallest that satisfies (23). The shedding amount corresponding to the shearing rate K is determined as the stabilization control amount. where E _C (k)
are calculated and set in advance off-line for possible shear patterns.

In addition, in the above embodiment, the inertia constant M ₃ is assumed to be provided as the information TS ₃ in FIG.
It is also possible to set this to a constant value and omit the transmission path for the information TS ₃ . Similarly, for information TS ₁ or TS ₂ in Figure 2, each mechanical input and electrical output
P _M1 , P _e1 ; Instead of P _M2 , P _e2 , both difference information (P _M1
−P _e1 ) and (P _M2 −P _e2 ) alone can achieve the same effect. Also, in information TS ₁ in Figure 2,
It is also possible to consider a method in which the inertia constant M ₁ is set to a constant value and the inertia constant M ₁ is not transmitted. Furthermore, when there is no generator group G ₃ that does not accelerate or decelerate, it is possible to use this method by setting M ₃ =0.

As described above, according to the system stabilization method of the present invention, based on the energy method, the mechanical input P _M1 of the equivalent acceleration generator, the inertia constant M ₁ , the electrical output P _e1 , the mechanical input value P of the equivalent deceleration generator _M2 , inertia constant _M2 , electrical output P _e2 , and, if necessary, the inertia constant _M3 of an equivalent generator that does not accelerate or decelerate, it is easy to calculate the accuracy and failure rate by removing the influence of the actual accident point and accident type. This has the effect of providing a system stabilization method that can significantly improve system stability.

[Brief explanation of the drawing]

Figure 1 is a system configuration diagram of a conventional system stabilization method, Figure 2 is a configuration diagram showing a system stabilization device to which this invention method is applied, and Figure 3 is a flow diagram of a stabilization control algorithm according to this invention. Figure 4 is a circuit diagram showing a two-system model for deriving the potential energy necessary to explain the operation of the device, and Figure 5 is an actual system and a hypothetical system drawn to explain the operation of the example in Figure 2. It is a power phase difference angle curve diagram showing the difference factor Δδ in potential energy between 1... power system, 20... central processing unit or
CPU, T ₁ , T ₂ , T ₃ ...Measurement and transmission equipment, G ₁ ...
...accelerating generator group or its equivalent aggregated generator,
G ₂ ... Generator group that decelerates or its equivalent aggregated generator, G ₃ ... Generator group that does not accelerate or decelerate or its equivalent aggregated generator, TS ₁ , TS ₂ , TS ₃ ... Information. In addition,
In the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. In response to an accident in a power system that connects a group of accelerating generators that accelerate due to a short circuit or ground fault in the power system, and a group of decelerating generators that decelerate due to the accident, the active power during the accident shall be reduced. The amount of change is determined to obtain the stored energy value accumulated during the accident, and the stored energy value is compared with an index predetermined as the stability of the power system, and the generators of the deceleration generator group are determined. In the system stabilization method, which determines the out-of-step of the power system by determining the flow rate and interruption, each electric output of the acceleration generator and the deceleration generator is calculated to determine the stable equilibrium point and unstable equilibrium point of the system. , and derive the potential energy value at the above unstable equilibrium point,
From this potential energy value, a corrected energy value corresponding to the actual system is identified, and the corrected energy value and the above-mentioned accumulated energy value are compared with each other, and it is determined that the capacity of the generators in the above-mentioned reduction generator group is insufficient. 1. A system stabilization method, characterized in that the reduction generator group is additionally cut and cut by calculating the cut and cut.