JPH0474931B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a system stabilization method for preventing synchronization between generators after an accident occurs in an electric power system, resulting in instability and collapse of the system. It is something.

Conventionally, this type of method has been shown in FIG. In Figure 1, A is the accident detection end;
B is the power plant to be controlled, 1 is the central processing unit (hereinafter referred to as
(abbreviated as CPU), and the CPU is
The fault signal F ₀ is sent to the power plant B to be controlled from the CPU 1, and the sheath break command signal CB is sent from the CPU 1 to the power plant B to be controlled.

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 signal F ₀ to the CPU 1. on the other hand,
In CPU 1, by comparing with the value of advance power flow comparison X ₁ or predetermined accident condition comparison X ₂ ,
It is determined whether or not it is necessary to partially shear off the generator, and if necessary, it issues a sheath cutoff command signal CB to the power plant B to be controlled.

Conventional system stabilization methods are configured as described above, so as the number of fault detection terminals increases, the amount of information to be transmitted increases, and it becomes difficult to determine the conditions to be set. In the case of an accident, it is not possible to distinguish between the fault points, so if the amount of damage varies depending on the fault point within the same power transmission line, it is difficult to accurately determine this.

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 an energy method and calculate the necessity and amount of interruption using the energy method by accurately determining the kinetic energy during an accident using electrical output value data, etc. It is an object.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings. In Figure 2, _G1 is a generator group that accelerates due to an accident such as a short circuit or ground fault that occurs in the grid;
G ₂ is a generator group (including pumped storage generators) that is decelerated due to the accident, G ₃ is a generator group that does not accelerate or decelerate due to the accident, and the inertia constant is when each of them is equivalently aggregated into one unit. , mechanical input value, and electrical output value as M ₁ , P _M1 , P _e1 ; M ₂ , P _M2 P _e2 ; M ₃ , P _M3 ,
Let P _e3 and the phase angles of the respective transient reactance back voltages be δ ₁ , δ ₂ , and δ ₃ .

In addition, 2 is a central processing unit (hereinafter abbreviated as CPU) that implements the stabilization method according to the present invention.
is the information sent from generator group G ₁ to CPU 2, and information B is the information sent from generator group G ₂ to CPU 2.
Further, information C indicates information sent to the CPU 2 from the generator group _G3 .

Specifically, information A includes an inertia constant M ₁ , an opportunity input value P _M1 , and an electrical output value P _e1 , and information B also includes an inertia constant M ₂ , a mechanical input value P _M2 and an electrical output value P _e2 , and information C represents the inertia constant M ₃ etc. These pieces of information A, B, and C are measured and transmitted by the respective measurement and transmission equipment.
It is transmitted to the CPU 2 via T ₁ , T ₂ , and T ₃ .

The CPU 2 uses this information to implement a stabilization control algorithm according to the flowchart of FIG. 3 based on the energy method.

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, 3 is a judgment block that compares the magnitude of this kinetic energy K _M with a preset critical energy E _C , and 34 is a block 35 that stops the algorithm by determining that it is stable when K _M < E _C.
36 is a processing block that determines instability when K _M ≧ E _C and moves to determining the stabilizing control amount (partial cutoff amount of the deceleration generator); 37 is a processing block that determines the minimum stability. A processing block for selecting the shearing ratio K, 38 a processing block for calculating the kinetic energy K M _′ assuming shearing and shearing at a shearing ratio K, and 39 a processing block for calculating the kinetic energy K _M ′ and the shearing ratio. Judgment block _that compares the magnitude with the critical energy E _C ′ which is set in advance assuming the shearing of the K portion, 40 is the shearing ratio of the shearing ratio K of the shearing amount of K _M A processing block 42 determines that the shearing can be stabilized by the shearing ratio _K and outputs a shearing signal to proceed to algorithm stop _block 41. This processing block determines that the quantity is insufficient, selects the next highest desperation rate, sets this as a new desease rate K, and returns to processing block 38.

Next, a method for calculating kinetic energy using online data will be explained with reference to FIG. 4. Hereinafter, subscript 1 indicates various quantities related to the equivalent generator that aggregates accelerator generator G1 into one unit using the short-circuit capacity method, subscript 2 indicates various quantities of the equivalent aggregated generator of deceleration generator G2, and 3 similarly Various quantities of the equivalent aggregated generator of the generator group G3 without acceleration/deceleration are respectively represented.
In addition, these equivalent generators are newly converted to G ₁ , G ₂ , G ₃
Expressed as. Normally, if the internal loss of the generator is omitted, the equation of motion of the generator becomes M _i δ¨ _i =P _Mi −P _ei (i=1 to 3) (1).

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) To find the kinetic energy K _M accumulated in the generator during a system accident, K _M = 1/2・M ₁ θ〓 _{1 2} ⁺ 1/2・M ₂ θ〓 ₂ ^{2 +} 1/2・M ₃
θ〓 ₃ ² ...(4) K _M = 1/2・M ₁ θ〓 ₁ ² +1/2・M ₂ θ〓 ₂ ² +1/2・M ₃ θ〓 ₃ ² −1/2 (M ₁ +M ₂ +M ₃ ) δ ₀ ² ...(5). In addition, in replacing equation (3), since the out-of-step development in the power system is determined by the relative relationship of the phase angle of the voltage behind the transient reactance of the generator, each deviation from the average value δ ₀ weighted by the inertia constant is It expresses the phase angle of the voltage behind the transient reactance of the equivalent generator.

Here, when deriving kinetic energy, there are two methods: one method assumes that the electrical output value of the generator is constant during the accident, and the other method takes into account changes in the electrical output of the generator. However, if the electrical output value of the generator is kept constant while the accident continues, the error shown in the shaded area A will occur due to variations in the operating time of the shisha cutter CB, as shown in Figure 4a. .
In this case, the worst fault clearing time is used as the fault clearing time, so the error becomes larger as the fault clearing time becomes faster. Furthermore, the electrical output value of the generator during the actual accident is
Since it is not constant as shown in the curve in Figure 4b, if the kinetic energy is determined by assuming that the electrical output is constant during the accident as shown in the curve in Figure 4b, the error shown in the shaded area B in Figure 4b is will also occur.
Since these two errors can greatly affect stability determination and shearing amount, in the present invention,
A method is adopted in which the kinetic energy is determined by actually measuring the electrical output value of the generator at each instant during the accident and integrating it during the accident. In other words,
According to the device of this embodiment, since accurate kinetic energy is derived along the curve shown in FIG. 4b, it is possible to prevent erroneous judgments, errors, and errors caused by the above-mentioned errors.

Therefore, as shown in Figure 4a and b, if the accident duration time is t _f , then from equation (1) mentioned above, δ〓=∫ ^tf / ₀ ΔP _i dt/M _i (However, ΔP _i = P _Mi − _{P ei} )……(
6) becomes. Here, the integral in equation (6) is sampled at regular intervals, and is executed according to the following equation using online data (ΔP _i )j of ΔP _i .

On the other hand, for generator G ₃ without acceleration/deceleration, P _M3 −P _e3 = 0 ...(8), so δ〓 ₃ = 0, and combining with equation (7), we get (5)
Substituting into the expression becomes. Therefore, now X= _{o 〓} ^{j=1 ΔP} _1i・_Δt ／P _M1 ……(10 _{) M} 1/2 {(M ₁ −M ₁ ² /M ₁ +M ₂ +M ₃ )(P _M1 /M ₁ ) ² X ² −2
M ₁・M ₂ /M ₁ +M ₂ +M ₃ (P _M1 /M ₁ ) (P _M2 /M ₂ )X・Y + (M ₂ −M ₂ ² /M ₁ +M ₂ +M ₃ ) (P _M2 /M ₂ ) ² Y ² }……(12
) becomes.

This equation (12) is based on the inertia constants M ₁ , M ₂ , M ₃ of each equivalent intensive generator G ₁ , G ₂ , G ₃ and each equivalent intensive generator G ₁ ,
Since the mechanical input values P _M1 and P _M2 of G ₂ are fixed data, ΔP _1i and ΔP _2j are measured at each instant, and the above (10),
It can be derived by finding X and Y from equation (11). Therefore, it has the effect of being able to determine stability and shearing amount at high speed.

Next, assuming the critical energy set in advance, that is, the potential energy at the unstable equilibrium point after the accident is cleared, as E _C , K _M ≧ E _C → unstable K _M ＜ E _C → stable ……(13) This makes it possible to make a judgment and predict whether or not a step-out phenomenon will occur.

Next, a method for determining the stabilization control amount, that is, the partial shear interruption of the deceleration generator when it is determined to be unstable using equation (1), will be explained. If this shearing ratio is k, it is considered that the inertia constant M ₂ of the reduction generator group has changed to M ₂ ′, that is, M ₂ ′ = (1−k) M ₂ ……(14) ( δ ₀ in equation 2) is δ ₀ ′=M ₁・δ ₁ +M ₂ ′・δ ₂ +M ₃・δ ₃ /M ₁ +M ₂ ′
+M ₃ ...(15), and the kinetic energy of equation (5) is K _M ′=1/2・M ₁・δ ₁ ² +1/2・M ₂・δ ₂ ² +1/2・
M ₃・δ ₃ ² −1/2 (M ₁ +M ₂ ′+M ₃ )・δ ₀ ′……(16). However, equations (6) and (7) remain unchanged.

Therefore, when formula (16) is expressed by X and Y in formulas (10) and (11), K _M ′=(M ₁ −M ₁ ² /M ₁ +M ₂ ′+M ₃ )(P _{M 1} /M ₁ ) ²・X ² −2
M ₁・M ₂ ′/M ₁ +M ₂ ′+M ₃ (P _{M 2} /M ₁ ) (P _{M 2} /M ₂ ′)
Y + (M ₂ ′−M ₂ ′ ² /M ₁ +M ₂ ′+M ₃ ) (P _{M 2} /M ₂ ′)・Y ² …
...(17), and if the critical energy after partial shearing of the reduction generator is E _c ′, then K _M ′<E _C ′ ...(18) corresponds to the smallest shearing ratio K that satisfies the following. The stabilization control amount is determined as the stabilization control amount. Here, E _C ′ is calculated and set online in advance for possible shear patterns.

In the above embodiment, the information C in FIG. 2 is the inertia constant M ₃ of the equivalent aggregated generator G ₃ without acceleration/deceleration.
However, it is clear that it is also possible to set this to a constant value and omit the transmission path for the information C. Similarly, in information A or B in FIG. 2, each equivalent aggregated generator G ₁ ,
Mechanical input value of G ₂ , electrical output value P _M1 , P _e1 ; P _M2 ,
Instead of P _e2 , its difference signal (P _M1 − P _e1 ), (P _M2 −
The same effect can be achieved by transmitting only P _e2 ). or,
In information A in Figure 2, the equivalent aggregate acceleration generator
It is easy to consider a change in which the inertia constant M ₁ of G ₁ is set to a constant value and the inertia constant M ₁ is not transmitted. or,
When there is no equivalent aggregate generator G ₃ that does not accelerate or decelerate, it is possible to apply the present invention by setting M ₃ =0.

As described above, according to the system stabilization method of the present invention, the mechanical input value P _M1 , the inertia constant M ₁ , and the electrical output value of the equivalent aggregated acceleration generator are determined based on the energy method.
P _e1 , the mechanical input value P _M2 of the equivalent integrated deceleration generator, the inertia constant M ₂ , the electrical output value P _e2 , and the inertia constant M ₃ of the equivalent integrated generator that does not accelerate or decelerate.It is easier to identify the actual accident point and accident type. This has the effect of providing a system stabilization method that eliminates the effects of , and can determine accuracy and disconnection.

[Brief explanation of the drawing]

Fig. 1 is a schematic block diagram showing a system of a conventional grid stabilization method, Fig. 2 is a block diagram showing a grid stabilizing device to which this invention method is applied, and Fig. 3 is a diagram of a stabilization control algorithm according to this invention diagram. Flow diagram, No. 4a shows the error A due to variation in the operation of the shingle breaker.
FIG. 4B is an explanatory diagram showing the difference between the two methods in the energy estimation operation used to determine the amount of shear. 1, 2...Central processing unit or CPU, A,
B, C...information, _G1 ...acceleration generator group or its equivalent aggregated generator, _M1 , _M2 , _M3 ...inertia constant,
G ₂ ...Reduction generator group or its equivalent aggregated generator,
P _M1 , P _M2 , P _M3 ... Machine input value, G ₃ ... Generator group without acceleration/deceleration or its equivalent aggregated generator, P _e1 ,
P _e2 , P _e3 ... electrical output value, T ₁ , T ₂ , T ₃ ... measurement and transmission device.

Claims (1)

[Claims] 1 Using online information from a group of generators that accelerate due to an accident such as a short circuit or ground fault in the power system, a group of generators that decelerate due to the above accident, and a group of generators that do not accelerate or decelerate due to the above accident. In a system stabilization method that maintains synchronization between the generators by cutting off part of the generator group that decelerates in the event of an accident, the energy method is used to determine stability and the generator group that decelerates. When determining the shearing rate of a group of aircraft, the kinetic energy value accumulated during the accident and the kinetic energy value for the above shearing rate are taken into account, taking into account changes in generator active power during the accident and changes in accident duration. is accurately determined, and furthermore, a predetermined critical energy value and a critical energy value corresponding to the above-mentioned shearing ratio are compared with the above-mentioned kinetic energy value to determine stability, and the minimum above-mentioned shearing ratio is determined and the above-mentioned deceleration is performed. A system stabilization method characterized by reducing the power outage of a group of generators.