JP2007181387A - Method for determining power system transient stability and its equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which accurately groups power generators into stable and unstable ones, in consideration with the accumulated energy during the accident and the conditions of a system after the accident has been removed when a supposed accident has occurred. <P>SOLUTION: For each of the supposed accidents to be set in and after a supposed accident setup step 12, this power system transient stability determination method comprises a stability simulation step 13 for calculating the detailed stability of a power system by using the initial condition of the power system, a 2-generator model creation step 14 for creating an equivalent 2-generator model based on the power generator internal voltage vector and power generator's effective power output obtained in the preceding step and the preset power generator classification information, a step 15 for estimating a system admittance between two-condensed power generators which constitutes this 2-generator model, and a stability determination evaluation step 16 for determining stability by an extended equal area criterion. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a power system transient stability determination method and apparatus for determining the power system transient stability against an assumed accident.

  In general, many generators are connected to the power system, and each generator performs a synchronous operation with each other and supplies the generated power to the power system. In such a power system, when a system fault occurs, the fault section is determined by the operation of the protection relay, the circuit breaker is opened, and the fault section is removed. In general, at this time, the surplus energy that cannot be sent to the generator while the grid fault is continuing becomes the acceleration energy of the generator, and the generator accelerates. Immediately after the accident is removed, power can be sent and the accelerating generator decelerates. However, some generators with high acceleration energy will cause step-out without returning to synchronous operation. As a result, it becomes impossible to operate while maintaining the stability of the power system.

  Therefore, when a grid fault occurs, the stability of the power system is determined promptly, and if necessary, some generators connected to the power system are shut off and the remaining generators in the power system are removed. It is necessary to stabilize the power system. Here, it is indispensable to quickly determine the transient stability of the power system when a system fault occurs in the power system.

Conventionally, there are several determination methods for determining the transient stability of a power system.
The power system transient stability determination method is a method of determining stability by performing a stability simulation and grasping the behavior of the generator based on the simulation result. In other words, this stability simulation is a discrimination of stability based on the so-called extended equal area method, focusing on the acceleration energy and deceleration energy of the generator group in order to speed up the calculation and reduce the enormous amount of calculation. Is the method.

  However, this stability determination method is difficult to formulate the relationship regarding P-δ in consideration of the dynamic characteristics of the generator and the generator control system that are actually in operation when formulating the problem concerning the extended equal area method. Since the formulation based on the simplified model assuming parameters such as the generator internal voltage and the machine input of the generator to be constant values is used, there is a problem in the accuracy of the stability determination.

As another power system stability determination method, a power system assumed accident stability evaluation method has been proposed (Patent Document 1).
As shown in FIG. 16, this assumed accident stability evaluation method performs a time domain simulation for obtaining the fluctuation of the generator after removing the accident in consideration of the dynamic characteristics of the generator for each assumed accident. The state data of the generator obtained by is read (101). Then, after dividing the plurality of generators connected to the power system into two groups according to the magnitude of the phase angle of each generator after removing the accident, two equivalent power generations are performed based on a predetermined arithmetic expression. (102). In other words, a one-dimensional classification method is used that divides into two groups based on the magnitude of the generator phase angle after accident removal.

  Furthermore, after the generator group divided into the two-machine system as described above is equivalently replaced with the one-machine infinite system (103), the corrected motion after the accident removal is performed using the simulation result after the accident removal described above. The energy is calculated (104). Further, a curve between the generator active power output P and the generator phase angle δ after the accident removal of the equivalent one machine infinite system, that is, a P-δ curve is estimated (105).

  By the way, since the P-δ curve of the equivalent single-machine infinite system is a sine curve, the system parameter for obtaining the active power output of the generator shown in the P-δ curve is a nonlinear function including a trigonometric function. Based on the formulation, the simulation results after the accident removal and the generator phase angle are used to estimate using the least-squares method, and by using the obtained system parameters, the generator's effective power output is finally obtained. Ask for.

Further, after obtaining the unstable equilibrium point after the accident removal using the estimated P-δ curve after the accident removal (106), the deceleration area is calculated from the unstable equilibrium point, and this deceleration area and the aforementioned The stability is determined from the corrected kinetic energy thus obtained (107).
JP-A-11-243644

  However, all of the above power system stability determination methods are formulated by a simplified model assuming that the generator internal voltage is constant. The reason is that the extended equal area method is formulated with a constant generator internal voltage. Here, when the generator internal voltage is constant, there is a problem that a control system model such as AVR of the generator field voltage cannot be considered.

  Furthermore, the latter method of assessing the stability of the assumed accident has grouped the generator group according to the generator internal phase angle immediately after the accident, so the stored energy during the accident is taken into account, but after the accident is removed The system status of As a result, it is difficult to appropriately divide the generator group connected to the target power system into a generator group that tends to be unstable and a generator group that tends to be stable.

  In addition, the assumed accident stability evaluation method estimates the system parameters of the equivalent generator model using an average value, least squares method, etc. when creating a generator model equivalent to the two-machine system. As a result of the increase in unknown variables including the internal voltage, it is difficult to estimate properly.

  In addition, when applying the extended equal area method, it is necessary to divide a large number of generator groups connected to the power system into generator groups that tend to be unstable and generator groups that tend to be stable. In the evaluation method, assuming a one-machine infinite system or a power system connected by a long-distance transmission line, the method is limited to application to a system that can be easily classified in advance, or the magnitude of the generator internal phase angle immediately after the accident is removed It is limited to the grouping method focusing on. Originally, in a multi-machine system to which many generators are connected, the severity of transient stability is affected by the stored energy during the accident and the system state of the power system after the accident is removed. The generator internal phase angle alone may not be able to group correctly.

  The present invention has been made in view of the above circumstances, and in the event of an assumed accident in a multi-machine system, considering the accumulated energy during the accident and the system state of the power system after the accident has been removed, It is an object of the present invention to provide a method and apparatus for determining the transient stability of a power system that can be accurately classified into generator groups having a stable tendency.

  In order to solve the above-mentioned problem, an invention of a transient stability determination method for an electric power system according to claim 1 is an initial state estimation input step for estimating and calculating the most probable initial state of the electric power system as a transient stability determination target. And an assumed accident setting step for setting an assumed accident for the initial state of the power system, and an initial state input from the initial state estimation input step for each assumed accident set in the assumed accident setting step. Stability simulation processing step for calculating the detailed stability of the power system, a generator internal voltage vector and a generator active power output that are part of the stability calculation result obtained by the stability simulation processing step, and presetting A two-machine model creation step of creating an equivalent two-machine model based on the generated generator classification information, and the creation step A system admittance estimation step for estimating an equivalent system admittance between the two reduced generators constituting the two-system model created in step 2, a system admittance estimated in this estimation step, and the stability calculation result And a stability discrimination evaluation step for obtaining a stability discrimination result such as stability discrimination and quantitative evaluation of stability by the extended equal area method.

  Further, the invention of the transient stability determination method for a power system according to claim 2 is the stability obtained in the stability simulation processing step instead of the two-machine model creation step which is a part of the above-described components. Create an equivalent two-system model based on the calculated generator internal power vector, which is a part of the calculation result, and the generator active power output simplified by a predetermined method, and preset generator classification information The two-system simple model creation step is used, and instead of the system admittance estimation step, the two reduced generators constituting the two-system model created in the two-machine simple model creation step are connected. The system parameter estimation step of estimating a system parameter from the product of the equivalent system admittance and the generator internal voltage is used.

  According to a third aspect of the invention, the power system transient stability determination method performs stability calculation for each assumed accident set in the assumed accident setting step as the generator classification information setting process described above. The generator internal phase angle calculation step after the accident removal for calculating the internal phase angle of the system after the removal of the assumed accident of each generator, and each generator determined by the internal phase angle and the stability simulation processing step of the system after the removal of the assumed accident The respective phase angle deviations of the generator internal phase angle in the initial state of the power system with respect to the internal phase angle immediately after the accident removal of the X axis and Y axis respectively, and the generator unit inertia constant belonging to each phase angle deviation A two-dimensional phase angle grouping processing step for performing grouping of each generator by setting the considered average value as the X-axis threshold value and the Y-axis threshold value. The features.

  According to a fourth aspect of the invention, there is provided a method for determining a transient stability of an electric power system, wherein the internal phase angle immediately after the accident removal of the angular generator obtained by the stability simulation processing step is set as the above-described generator classification information setting process. A two-dimensional energy index grouping process step for grouping the generators with the acceleration energy and deceleration energy at the time of an accident obtained from the angular velocity as the X axis and the Y axis, respectively, is provided.

  In addition, the invention of the transient stability determination method according to claim 5 is the constituent element of claim 1 or claim 2, and an unstable accident based on the stability determination result by the stability determination evaluation step for a plurality of assumed accident cases. A stability screening step for extracting cases, and an unstable accident case extracted in this step, using the stability simulation processing step, a stability simulation is performed within a predetermined analysis target time range. A detailed stability verification step for verifying stability and instability is added.

  According to a sixth aspect of the invention of the power system transient stability determination device, in place of the stability determination evaluation step according to the first aspect, when the assumed accident causes the switch to be reclosed due to an unbalanced accident. A post-reclosed curve approximation step for estimating the post-reclosed P-δ curve when the pre-reclosed P-δ curve is switched to another post-reclosed P-δ curve with the reclose as a boundary; A reclosing circuit that calculates deceleration energy based on the system admittance estimated in the system admittance estimation step and the stability calculation result separately before and after the switching of the -δ curve, and performs the stability determination and quantitative evaluation of the stability A stability discrimination evaluation step with a sequence is provided.

  Further, the invention of the power system transient stability determination device according to claim 7 is a method of replacing the post-accident generator internal phase angle calculation step according to claim 3, wherein the power flow calculation is not converged according to the assumed accident. If this is the case, a simple impedance flow calculation step is performed to calculate the power flow by setting the impedance of the transmission line subject to the assumed accident to a size that can be virtually converged, and to determine the generator internal phase angle of the system after the assumed accident. It is characterized by that.

  Furthermore, the invention of the power system transient stability determination device according to claim 8 is characterized in that, in place of the accident-removed generator internal phase angle calculation step according to claim 3, of the stability calculation results, the detailed stability A generator internal phase angle extraction step is provided which substitutes the internal phase angle of each generator at the time of simulation termination as the generator internal phase angle of the post-accident system.

  Furthermore, the invention of the power system transient stability determination device according to claim 9 is the power system transient stability determination device for determining the transient stability of the power system to which a plurality of generators are connected. Initial state estimation input means for estimating and calculating the most probable initial state of the power system to be determined, an assumed accident setting means for setting an assumed accident for the initial state of the power system, and this assumed accident setting means Stability simulation processing means for calculating the detailed stability of the electric power system using the initial state input from the initial state estimation input means for each assumed accident set from the above, and the stability obtained by the stability simulation processing means The equivalent two-machine model based on the generator internal voltage vector and the generator active power output, which are part of the degree calculation result, and the preset generator classification information A two-machine model creating means for creating the system, a system admittance estimating means for estimating an equivalent system admittance between the two reduced generators constituting the two-machine model created by the creating means, and the estimation Stability discrimination evaluation means for acquiring stability discrimination results such as stability discrimination and quantitative evaluation of stability by the extended equal area method based on the system admittance estimated by the means and the stability calculation result .

  According to the present invention, when an assumed accident occurs in a multi-machine system, a generator group that tends to be unstable and a generator group that tends to be stable, considering the stored energy during the accident and the system state of the power system after the accident is removed. Thus, it is possible to provide a power system transient stability determination method and apparatus that can be classified accurately.

Embodiments of the present invention will be described below with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram showing a flow of processing for explaining a first embodiment of a transient stability determination method for a power system according to the present invention.
This power system transient stability determination method is provided with a stability determination processing device 2 constituted by a CPU, and the transient stability of a power system (including a power system model) 1 to be determined according to a predetermined processing procedure. A discrimination process is performed.

  The power system 1 to be a stability determination target is configured as a so-called multi-machine system in which a large number of generators and loads are connected to each place of a large number of linked buses constituting a backbone system through transformers and power lines, respectively. Yes. As a result, when an accident such as a short circuit, ground fault, or disconnection occurs in either the power line or the associated bus, depending on the accident point, the phase difference of the generator with a relatively small power generation capacity near the accident point is 90 degrees. May be exceeded. In this case, the synchronous operation of the generator becomes difficult, and the generator will step out. If there is an out-of-step generator, the transient stability becomes unstable, and the generator group tends to be stable and the generator group tends to be unstable.

  Therefore, in the stability determination processing device 2, when a system fault occurs, the transient stability of the power system is accurately determined and classified into a generator group with a stable tendency and a generator group with an unstable tendency. It can be effectively used for control of generator shutoff.

  The transient stability determination method by the stability determination processing device 2 includes an initial state estimation input step 11 for estimating and calculating an initial state of the power system 1 to be subjected to transient stability determination, and an assumption that an assumed accident of the power system 1 is set. Accident setting step 12, stability simulation processing step 13 for performing stability calculation using the initial state of the target power system 1 for each assumed accident assumed in advance, two-system model creation step 14, and system admittance estimation It consists of step 15 and stability discrimination evaluation step 16.

  The initial state estimation input step 11 takes in telemeter information required in advance from the target power system 1 and on / off information of various switches installed in the power system 1, and uses the state estimation calculation or the like to initialize the initial state of the power system 1. Is estimated and input to the stability simulation processing step 13. Here, the initial state of the electric power system 1 is the voltage, phase angle, and voltage of each node of the current system (for example, each bus, generator connection bus, each branch point of the system, etc.) in the operating state before the assumed accident. It is a generic term for active power, reactive power, and other necessary initial state quantities. In addition, the initial state of the power system 1 includes not only the current system but also an initial state based on a future system based on a future operation plan (such as during peak summer power consumption). In the case of the initial state based on the future system, it is obtained by tidal current calculation.

  In the assumed accident setting step 12, a plurality of assumed accident data D1 is stored in the database 3 in advance, and the assumed accident data D1 is read from the database 3 for each assumed accident and input to the stability simulation processing step 13. Here, the assumed accident means accident data assumed for each number of transmission lines constituting the power system 1, for each accident location of each transmission line, and for each accident pattern. Examples of the accident pattern include a one-line ground fault, a two-line ground fault, etc. due to lightning strikes.

  The stability simulation processing step 13 uses the initial state quantity input from the initial state estimation input step 11 for each assumed accident set from the assumed accident setting step 12, and the behavior of the power system 1 (transient stability). That is, the detailed stability of the electric power system 1 is calculated and output as the stability calculation result D2. Specifically, the dynamic characteristics of the generator at the time of the assumed accident are expressed by a nonlinear ordinary differential equation, and the movement of each variable that changes from time to time is calculated by a numerical integration method (for example, the fourth-order Runge-Kutta method). In this embodiment, the detailed stability simulation is repeatedly performed until about 0.3 seconds elapse with a step width of 0.01 seconds, for example, with the accident removal time as the base point. Therefore, it is only necessary to calculate the dynamic characteristics from 0.3 seconds to 0.5 seconds from the time of the occurrence of the accident, and considering that the stability calculation normally performed takes about 5.0 seconds. Dynamic characteristics can be calculated at a speed about 1/10.

  In the two-machine model creation step 14, the initial transient internal voltage vector (magnitude, phase angle) and the generator active power output, which are the stability calculation result D 2 obtained in the stability simulation processing step 13, are stored in the database 3 beforehand. An equivalent two-system model is created based on the stored generator classification information D3. Here, as shown in FIG. 2, the generator classification information D3 is stored separately for each assumed accident, for example, instability-generator information and stability-generator information. For example, only generator information with an unstable tendency may be specified, and other generators may be handled as generators with a stable tendency. Alternatively, only generator information with a stable tendency may be specified and other generators may be unstable. May be treated as a trend generator.

  In the system admittance estimation step 15, since the equivalent system admittance connecting two equivalent generators is unknown in the 2-machine model created in the 2-machine model creation step 14, it is equivalent using the least square method. A system parameter (admittance) D4 in a two-machine model is estimated.

  The stability discrimination evaluation step 16 performs stability discrimination and quantitative evaluation of the stability using the extended equal area method based on the system admittance D4 estimated in the system admittance estimation step 15 and the detailed stability calculation result D2 described above. The stability determination result D5 is output.

Next, the operation of the above power system transient stability determination method will be described in detail.
First, in a predetermined area of the database 3, generator classification information D <b> 3 including all assumed accident data D <b> 1 assumed in the electric power system 1, generator information of unstable tendency and generator information of stable tendency for each assumed accident. Is stored in advance.

  In a state as described above, when a transient stability determination command (not shown) is input from the outside, an initial state estimation input step 11 is activated, and the initial state of each node of the current power system 1 in the operating state before the assumed accident is determined. The state estimation calculation is performed and input to the stability simulation processing step 13. In the assumed accident setting step 12, one assumed accident data is extracted from the database 3 according to a predetermined order and set in the stability simulation processing step 13.

In the stability simulation processing step 13, detailed stability calculation is performed on the assumed accident data set in the assumed accident setting step 12 using the initial state of the target power system 1, and the power system 1 at the time of the assumed accident occurrence is calculated. Calculate the behavior of the generator, especially the behavior of the generator. That is, the stability simulation processing step 13 calculates the dynamic characteristic that becomes the behavior of the generator using the differential equations (1) to (5) described below for each generator, and outputs it as the stability calculation result D2. .

Where δ: generator internal phase angle, ω: generator rotor angular velocity, ω ₀ : reference angular velocity (= 2πf _0, f ₀ is the fundamental frequency), M: generator unit inertia constant, Pm: machine input, Pe: electrical output, D: damping coefficient, _e'q: q-axis transient internal voltage, _T'd0: d JikuHirakiro transition time constant, T _"d0: d JikuHirakiro initial transient time constant, T" _q0: q JikuHirakiro subtransient Time constant, E _fd : Internal voltage proportional to field voltage, E _I : Internal voltage proportional to field current, Ψ _kd : Magnetic flux of d-axis damper circuit, Ψ _kq : Magnetic flux of q-axis damper circuit, i _d : d-axis armature current, i _{q: q-axis armature current,} i _kd: d-axis damper current, i _kq: q-axis damper current, r _a: armature resistance, X _d: d-axis synchronous reactance, _X'd: d-axis transient reactance, X ″ _d : d-axis initial transient reactance, X _q : q-axis synchronous reactance, X ′ _q : q-axis transient reactance, X ″ _q : q-axis initial transient reactance, X ₁ : leakage reactance.

By the way, various quantities belonging to the right side of the expressions (1) to (5) can be obtained from the algebraic equations shown in the following expression (6) and the following expressions (7) to (14).

Where E _G : Generator connection node voltage vector
E _L : Load node voltage vector
Y _GG : Admittance matrix between generator connection nodes
Y _GL : Admittance matrix between generator connection node and load node
Y _LG : Admittance matrix between load node and generator connection node
Y _LL : Admittance matrix between load nodes
e _G : Generator internal voltage vector y _G : Generator internal admittance
I _L : Load node current vector Further, generator internal current I _G , generator active power output _Pe , d-axis armature current i _d , q-axis armature current i _q , d-axis damper current i _kd , q-axis damper The current i _kq , the internal voltage E _I proportional to the generator field current, and the internal voltage E _fd proportional to the field voltage are obtained from the following equations.

In the equations (7) to (14), Re: real part, Im: imaginary part, and f: function of f _AVR .

Furthermore, in the method of the present invention, when the field voltage control system (AVR) and the governor control system (GOV) of the generator are taken into account, the movements of the state variables of AVR and GOV are calculated based on the following equations.
dy _AVR / dt = F _AVR (t, y _{AVR) (15)}
dy _GOV / dt = F _GOV (t, y _{GOV) (16)}
However, in the equations (15) and (16),
y _AVR : AVR state variable vector
F _AVR : AVR control characteristic function vector
y _GOV : GOV state variable vector
F _GOV : GOV control characteristic function vector.
That is, in the method of the present invention, the calculation of the differential equations (15) and (16) expressed by vectors is newly added.

Therefore, as the stability simulation processing step 13 in the method of the present invention, the differential equations (1) to (5), (15), and (16) are used using the above equations (6) to (14). After calculating the quantities belonging to the right side of the equation, the quantities are substituted into the expressions (1) to (5), (15), and (16), and by solving these differential equations, Δt time later Calculate generator quantities. Based on these calculation results, the generator internal voltage vector e _G is obtained using the following equation (17), and the obtained generator internal voltage vector e _G is substituted into the equation (6) again. Repeat the calculation.

  In the above formula, sqrt represents √.

  As described above, in the stability simulation processing step 13, various quantities relating to each generator are calculated using differential equations, and various quantities relating to the entire system are calculated using algebraic equations. Although not shown, it is stored in an appropriate storage device, and the stability simulation is repeatedly performed while the time is advanced in units of 0.1 seconds, for example. In this embodiment, for example, it is repeated for 0.5 seconds, that is, 50 times.

  Thereafter, the stability simulation is repeatedly performed based on the initial state of the power system 1 for each assumed accident.

  Then, if various quantities that are the stability calculation result D2 are obtained by performing the stability simulation for each assumed accident, the process proceeds to the 2-machine model creation step 14 to obtain the state variable of the equivalent generator.

The two-machine model creation step 14 includes, for example, the generator unit function M, the generator active power output Pe, the generator internal voltage vector e _G , and the generator internal phase angle δ obtained in the stability simulation processing step 13 described above. Using the generator machine input Pm and other necessary quantities and the generator classification information D3 stored in the database 3, an equivalent two-machine model of the power system 1 is created by formulation.

  In the stability simulation processing step 13, since the stability simulation is performed based on the specified assumed accident, the equivalent generator of the generator group that tends to be unstable from the generator classification information D3 in the assumed accident (Reduced generator) G1 and an equivalent generator (reduced generator) G2 of a stable generator group can be easily extracted.

Therefore, in the two-system model creation step 14, the generator active power outputs P _E1 and P _E2 , which are the state variables of the equivalent generator, the generator internal voltages E _G1 and E _G2 , the generator internal phase angles δ1 ′ and δ2 The generator machine inputs P _M1 and P _M2 are obtained by calculating the following formula. Further, the two equivalent generators G1 and the equivalent generator G2 are connected by a reduced Y matrix (reduced admittance). As a result, an equivalent two-machine model of the power system 1 as shown in FIG. 3 can be created. Note that G11, G12, G22, B11, B12, and B22 in the reduced Y matrix in the figure are system admittances (system parameters).

  The subscripts i and j represented by symbols Mi and Mj etc. mean individual generator numbers 1, 2, 3,.

  In this two-machine model creation step 14, after an equivalent two-machine model is created based on the generator classification information D3, the process proceeds to a system admittance estimation step 15 to estimate the system admittance of the two-machine model.

In the system admittance estimation step 15, since the equivalent system admittance connecting the two equivalent generators G 1 and G 2 is unknown at the processing stage of the two-machine model creation step 14, the equivalent two-machine model is used by using the least square method. Estimate the system admittance. Specifically, for the reduced Y matrix shown in FIG. 3, G11 + jB11, G12 + jB12, G22 + jB22 and the above equations (18) to (23) are output as the stability calculation result D2 of the above-described stability simulation processing step 13. Substituting the state variables of the equivalent generator (P _E1 , P _E2 (= corresponding to Pe) and the generator internal phase angles δ1, δ2) after the accident removal of the assumed accident into the equivalent generator state variables The generator active power outputs P _E1 and P _E2 can be obtained from the following equations. Note that (1) of P _E1 (1) and P _E2 (1) is the equivalent of the stable tendency to the generator active power output P _E1 of the unstable generator G1 having an unstable tendency in 0.1 seconds after the removal of the assumed accident, for example. It represents the generator active power output P _E2 of the generator G2 and corresponds to one set. n is 0 after removal of the assumed accident. The time point of the simulation of stability calculation in n seconds is shown, which can be said to be the n-th set.

There are four parameters G11, G22, G12, and B12 that are desired to be obtained from the above formula. Therefore, if the generator active power output P _E , the generator internal voltage E _G , and the generator internal phase angle δ of the equivalent generator at two or more different points in time are obtained, the four grid admittances (system parameters ) G11, G22, G12, B12 can be obtained.

When the equations (28) to (31) are rewritten as a matrix, the following equation is obtained.

X, that is, the system admittance D4 (G11, G22, G12, B12) can be obtained.

  In this embodiment, a detailed stability simulation result of about 0.3 seconds in 0.01 second increments immediately after the removal of the assumed accident (that is, each group 2 from 30 groups (formulas (28) to (31)) Since it is a book, a solution can be obtained using 60 equations).

Further, a stability discrimination evaluation step 16 is executed. The stability discrimination evaluation step 16 uses the system admittance D4 (G11, G22, G12, B12) estimated by the system admittance estimation step 15, and the equation of the two-system model can be expressed by twice differentiation as follows. it can.

That is, equation (35) is a value obtained by differentiating δ in equations (1) and (2) twice in an unstable generator on the one side and shifting M to the right side. Equation (32) is a value obtained by differentiating δ in Equation (1) and Equation (2) twice in an equivalent generator with a stability tendency on the other aircraft side and shifting M to the right side. As generator internal voltages E _G1 and E _G2 , E _G1 (tx) and E _G2 (tx) at the time of calculation termination (tx) of the detailed stability simulation are used.

Next, assuming that δ = δ 1 −δ 2 and ω = ω 1 −ω 2, the equations (35) and (36) can be replaced as follows.

  This equation (39) corresponds to an infinite model.

Here, when the generator unit inertia constant is M, the generator machine input is P _M , and the generator active power output is Pe,
M = (M ₁ M ₂ ) / (M ₁ + M ₂ ) (40)
_{P M / M = (P M1} / M 1) - (P M2 / M 2) ...... (41)
Pe / M = P _e1 / M ₁ ) − (P _e2 / M ₂ ) (42)
It can be expressed as

Furthermore, from the equations (40) and (41), the generator machine input P _M is

It can be expressed as However, M _T = M ₁ + M _{2 (44)}
It is. Similarly, from the equations (40) and (42), the generator active power output Pe is

It can be expressed as Here, by substituting the equations (37) and (38) into the equation (45), the generator active power output Pe is
Pe = [M ₂ G ₁₁ E _G1 ²
+ M ₂ E _G1 E _G2 {G ₁₂ cos (δ ₁ −δ ₂ ) + B ₁₂ sin (δ ₁ −δ ₂ )}
-M ₁ G ₂₂ E _G2 ²
−M ₁ G ₁ E _G2 {G ₁₂ cos (δ ₂ −δ ₁ ) + B ₁₂ sin (δ ₂ −δ ₁ )}] M _T ⁻¹
...... (46)
It becomes.

Furthermore, if the generator active power output Pe is arranged as δ = δ ₁ −δ ₂ (∵δ ₂ −δ ₁ = −δ),
Pe = [(M ₂ G ₁₁ E _G1 ² −M ₁ G ₂₂ E _G2 ² )
+ (M ₂ E _G1 E _G2 B ₁₂ + M ₁ E _G1 E _G2 B ₁₂ ) sin δ
+ (M ₂ E _G1 E _G2 G ₁₂ -M ₁ E _G1 E _G2 G ₁₂ ) cos δ] M _T ⁻¹
= (M ₂ G ₁₁ E _{G 1} ² −M ₁ G ₂₂ E _G2 ² ) M _T ⁻¹ + E _G1 E _G2 B ₁₂ sin δ
+ (M ₂ −M ₁ ) E _G1 E _G2 G ₁₂ cos δM _T ⁻¹
= Pc + (Dsinδ + Ccosδ) (47)
However, in the equation (47),
Pc = M ₂ G ₁₁ E _G1 ² −M ₁ G ₂₂ E _G2 ² ) M _T ^{−1 (48)}
C = (M ₂ −M ₁ ) E _G1 E _G2 G ₁₂ cos δM _T ⁻¹ (49)
D = E _G1 E _G2 B _{12 (50)}
It becomes.

Therefore, the generator active power output Pe expressed by the equation (47) is
Pe = Pc + SQRT (C ² + D ² ) × sin (δ + ν)
= Pc + Pmax × sin (δ + ν) (51)
Can be replaced. However, in equation (51)
^{Pmax = SQRT (C 2 + D} 2) ...... (52)
ν = tan ⁻¹ (C + D) (53)
It becomes. SQRT means √.

Therefore, in the aforementioned equation (51), when the generator internal phase angle δ is taken on the horizontal axis and the generator active power output P is taken on the vertical axis, a Pe-δ curve as shown in FIG. 4 is obtained. Now, when an accident occurs at the operating point (a) during normal operation, the generator's active power output Pe cannot be transmitted to the power system 1, and the energy in the generator is accumulated, resulting in an accelerated state. The phase angle opens. After that, when the accident is removed, the generator's active power output Pe is supplied from the generator to the power system 1, so it jumps over the machine input P _M and moves along the Pe-δ line shown by the solid line. To go. In this case, the boundary of the mechanical input P _M, the energy area indicated by hatching after the accident and (ii) if is equal energy area (c) shown by oblique lines after the accident removed back to the line of mechanical input P _M and stability However, when the energy area (c) after the accident is removed is small, it shifts to an unstable state.

In FIG. 4, δa represents δ at the time of occurrence of the accident, and δc represents δ after the accident is removed. Further, δu and δ0 are solutions of P _M = Pc + Pmax × sin (δ + ν).

Therefore, the stability discrimination evaluation step 16 performs stability discrimination by the extended equal area method using the equation (51) and FIG. In this stability determination, ACC and DCC are calculated using the following equations (54) and (55), and stability determination is performed. ACC represents the time t _x of the kinetic energy censored calculation by the detailed model in stability simulation processing step 13 (acceleration energy). Further, DCC represents the deceleration energy of the time t _x has been aborted the calculation by the detailed model. That is, ACC is acceleration energy at a certain point in time (corresponding to (b) hatched portion in FIG. 4), and DCC is deceleration energy after a certain point in time (corresponding to (c) hatched portion in FIG. 4).

Further, after obtaining ACC and DCC using the equations (54) and (55), a value K serving as an index for determining stability is obtained using the following equations using these ACC and DCC.
K = {DCC (t _x ) −ACC (t _x )} / ACC _MAX (56)
Note that ACC _MAX = ACC _δ0 .

Then, using the stability determination index value K obtained by the equation (56), it is determined and evaluated whether it is stable or unstable under the following determination conditions.
K> 0 → stable
K = 0 → stability limit
K <0 → unstable
In the equation (56), since ACC (t _x ) is a positive value, the stability can be determined from the size of the area of the deceleration energy DCC (t _x ) and the acceleration energy ACC (t _x ). It becomes possible. That is, the acceleration energy ACC (t _x ) at the time point t _x is stable when the acceleration energy ACC (t _x ) is lower than the deceleration energy DCC (t _x ), and is unstable when the acceleration energy ACC (t _x ) exceeds the acceleration energy ACC (t _x ). Incidentally, t _x is in each accident aspect, in accordance with the relay operation of the accident aspects, may be the time that has elapsed 0.1 seconds after the accident removed.

Furthermore, in this embodiment, as apparent from the above equation (56), the difference between the deceleration energy DCC and the acceleration energy ACC, that is, the energy imbalance amount is divided by the maximum acceleration energy amount ACC _MAX and normalized. Therefore, for example, the stability due to an assumed accident between a plurality of points can be quantitatively evaluated. The value K serving as an index for determining stability is a value smaller than 1, but it can be determined that the larger K is, the farther away from the instability limit (K = 0).

  Therefore, according to the embodiment as described above, the detailed stability simulation can be performed at a time interval shorter than usual, and the stability against the assumed accident can be determined from the stability calculation result. Even in the case of discrimination, it is possible to grasp the degree of stability based on the quantified index.

  Further, in this embodiment, the formulation is formulated using the magnitude of the back voltage of the equivalent generator and the phase angle, and the system admittance is separated, so the convergence by the least square method is good and the solution is obtained stably. In particular, iterative calculations are unnecessary.

  Furthermore, by extracting unstable accident cases from many assumed accident cases, it is possible to perform detailed analysis in a short time specialized for unstable accident cases.

  Further, the power system that changes from time to time is calculated and analyzed at regular intervals using a quantified stability index, and thus approaches the stable region (K = 0) from the stable region (K> 0). Therefore, it is possible to monitor the approach to the stability limit and greatly contribute to the stable operation of the electric power system 1 because the state of transition to the unstable region (K <0) can be grasped.

(Second Embodiment)
FIG. 5 is a diagram showing a flow of processing for explaining the second embodiment of the stability determination method of the power system according to the present invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this power system stability determination method, the initial state estimation input step 11, the assumed accident setting step 12, the stability simulation processing step 13, and the stability determination evaluation step 16 are the same as those in the first embodiment.

  In this embodiment, the difference is that a two-machine simple model creation step 21 is used instead of the two-machine model creation step 14 of FIG. 1, and a system parameter estimation step 22 is used instead of the system admittance estimation step 15. It is used.

This two-machine simple model creation step 21 uses the generator internal phase angle obtained as the stability calculation result D2 and the generator active power output, etc., and is based on the generator classification information D3 stored in the database 3 in advance. Create an equivalent two-machine model. The system parameter estimation step 22 calculates the product of the system admittances G11 ′, G22 ′, G12 ′, B12 ′ and the generator internal voltage E _G in the equivalent 2-system model obtained in the 2-system simple model creation step 21. Has a function to estimate.

Next, the power system stability determination method as described above will be specifically described.
First, in the stability simulation processing step 13, the power system 1 is used by using the initial state quantity input from the initial state estimation input step 11 for each assumed accident set from the assumed accident setting step 12 as described above. (Transient stability), that is, the detailed stability of the power system 1 is calculated, and the stability calculation result D2 is obtained. In the present embodiment, after the accident is removed, the detailed stability simulation is repeatedly performed, for example, until about 0.3 seconds elapse with a step width of 0.01 seconds. The details are as described in the above formulas (1) to (17).

When the stability simulation processing step 13 is performed as described above and the stability calculation result D2 which is the stability simulation result is obtained, the two-system simple model creation step 21 is obtained in the stability simulation processing step 13. Using the generated generator active power outputs P _E1 and P _E2 , the generator internal voltage E _Gi , the generator internal phase angles δ1i and δ1j and the generator machine inputs P _mi and P _mj , and based on the generator classification information D3, The state variable of the equivalent generator is calculated by the following formula, and an equivalent two-machine model of the power system 1 as shown in FIG. 6 is created.

  The subscripts i and j represented by symbols Mi and Mj etc. mean individual generator numbers 1, 2, 3,.

Among the above equations, e ′ _q of the above-described equation (3) is used for the generator internal voltage E _Gi of the equation (2-3). However, in the present embodiment, E _Gi is estimated by including it on the system parameter side described later, and thus does not appear explicitly. (That is, use “1”). Further, although δ in the expression (1) is used in the expressions (22) and (23) described in the first embodiment, the expressions (2-4) and (2- Δ ₁ and δ ₂ used in equation (5) differ from the first embodiment in that δ ′ in equation (17) is used algebraically.

  Further, after an equivalent two-machine model is created in the two-machine simple model creation step 21, the process proceeds to a system parameter estimation step 22 to estimate the system parameters of the two-machine model. Here, the reduced Y matrix is represented by G11 ′ + jB11 ′, G12 ′ + jB12 ′, and G22 ′ + jB22 ′. However, each parameter is defined as follows.

G ₁₁ '= E _G1 ² G ₁₁
G ₁₂ '= E _G1 E _G2 G ₁₂
B ₁₂ '= E _G1 E _G2 B ₁₂
G22 '= E _G2 ² G ₂₂
These parameters G ₁₁ ′, G ₁₂ ′, B ₁₂ ′, and G 22 ′ are defined by the product of the system admittance and the generator connection node voltage. As a result, by defining as described above, the term of E _Gi disappears, and the expressions (28) to (31) described in the first embodiment are expressed by the following expressions (2-9) to (2- 12).

Here, there are four parameters G ₁₁ ′, G ₁₂ ′, B ₁₂ ′, and G 22 ′ to be obtained. Therefore, if the generator active power output P _E , the generator connection node voltage E _G , and the generator internal phase angle δ of the equivalent generator at two or more different times are acquired, the four system parameters G ₁₁ are obtained by the least square method. ', G ₁₂ ', B ₁₂ ', G 22', that is, the system parameter D21 (product of system admittance and voltage) shown in FIG. 5 can be obtained.

Therefore, when the above-described equations (2-9) to (2-12) are rewritten as a matrix, they can be expressed as follows.

When comparing the matrix and the first said described in the embodiment of (32) of the matrix, but has a (32) is a matrix containing the voltage E _G in the right-hand side matrix elements, ( In the expression 2-13), “1” is put in the element corresponding to the voltage E _G in the right-hand side matrix element, and the parameters G ₁₁ ′, G ₁₂ ′, B ₁₂ ′, and G 22 ′, which are new variables, are multiplied. It has become a matrix.

Therefore, the equation (2-13) is
z = H · x (2-14)
Then, using the method of least squares and transforming equation (2-14),
^{x = (H T H) -1} H Tz (T ^{represents a transposed matrix) (2-15)}
By solving, x ie, system parameters _{D21 (G 11 ', G 12} ', B 12 ', G22') Request.

The above way system parameters _{D21 (G 11 ', G 12} ', B 12 ', G22') After obtaining the executes stability determination evaluation step 16. The series of processes in the stability discrimination evaluation step 16 is as described in the first embodiment, and the description thereof is omitted here.

  Therefore, according to the embodiment as described above, the system parameter is estimated using the method of least squares with the product of the system admittance and the voltage as a parameter. It is possible to estimate the system parameters taking into account the voltage change, and to eliminate the complexity of voltage selection for the application of the extended equal area method. In addition, the same effects as those of the first embodiment are achieved.

(Third embodiment)
FIG. 7 is a diagram showing a flow of processing for explaining the third embodiment of the power system stability determination method according to the present invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As in the first embodiment, this power system stability determination method includes an initial state estimation input step 11, an assumed accident setting step 12, a stability simulation processing step 13, a two-system model creation step 14, a system admittance. In addition to the estimation step 15 and the stability discrimination evaluation step 16, the accident internal phase angle calculation after the accident removal that newly calculates the system power flow after the accident removal using the assumed accident data D1 set in the assumed accident setting step 12 Step 31 and a two-dimensional phase angle grouping processing step 32 are provided.

  In the third embodiment, the basic processing flow relating to power system stability determination is the same as that of the first embodiment. Particularly, the difference is that the generator classification information D3 ′ is obtained by a calculation formula using the initial state data of the power system, etc., instead of setting the generator classification information by a human.

Furthermore, it demonstrates concretely. First, when the generators are grouped, δ0 _i which is the generator internal phase angle D31 in the initial state in the power system 1 is obtained by power flow calculation and stability calculation. Here, “0” of δ0 _i represents an initial state, and i represents an arbitrary number of the generator. Also, the assumed accident data D1 is taken out from the assumed accident setting step 12 and sent to the generator internal phase angle calculating step 31 after the accident is removed.

In the post-accident generator internal phase angle calculation step 31, stability calculation is performed using the assumed accident data D <b> 1 obtained from the assumed accident setting step 12, and the internal phase angle D <b> 32 of the post-accident system of each generator is calculated. A certain δ2 _i is obtained. “2” represents after the assumed accident, and i represents an arbitrary number of the generator. Further, the generator internal phase angle calculation step 31 after accident removal takes out δ1i, which is the internal phase angle D33 immediately after the accident removal of each generator, from the stability calculation result D2, and sends it to the two-dimensional phase angle grouping processing step 32. To do. Here, “1” represents immediately after the accident is removed, and i represents an arbitrary number of the generator.

This two-dimensional phase angle grouping processing step 32 includes the generator internal phase angle D31 (δ0 _i ) in the initial state, the generator internal phase angle D32 (δ2i) of the post-accident system, and immediately after the accident removal of each generator. Using the internal phase angle D33 (δ1i), generator classification information D3 ′ classified into an unstable-generator group and a stable-generator group is obtained.

Next, the processing operation of the two-dimensional phase angle grouping processing step 32 will be described.
In general, the instability phenomenon of a generator is greatly influenced by two factors such as energy accumulation in the generator in an accident and the system state after the accident is removed.
Therefore, when these factors are taken into consideration, attention is paid to the above-described three phase angles.
(1) Generator internal phase angle D31 (δ0) of the initial power system: internal phase angle in the initial state
(2) Generator internal phase angle D33 (δ1) immediately after the accident is removed: Internal phase angle immediately after the accident is removed in the detailed stability calculation
(3) Generator internal phase angle D32 (δ2) of the post-accident system: This is an internal phase angle obtained by tidal current calculation and initial value calculation of the post-accident system.

Then, using these three phase angles δ0, δ1, and δ2, a two-dimensional coordinate as shown in FIG. 8 is considered. That is, (δ1-δ0) representing the characteristics during the accident is taken as the Y-axis, and (δ2-δ0) representing the characteristics after the accident is removed is taken as the X-axis. Further, the weighted average values (δ1-δ0) k and (δ2-δ0) k (k is an arbitrary integer) taking into account each generator unit inertia constant M are set as threshold values, and are shown on two-dimensional coordinates, Perform machine grouping. The Y-axis threshold value (δ1-δ0) k and the X-axis threshold value (δ2-δ0) k can be expressed by the following equations.

  On the two-dimensional coordinates as described above, the generators that are larger than the X-axis threshold value and larger than the Y-axis threshold value are set as group 1, and the other generators are set as group 2, and these group 1 , 2, generator classification information D3 ′ can be extracted.

  Further, in the two-dimensional phase angle grouping processing step 32, as shown in FIG. 9, generators larger than the X-axis threshold value are set as group 1, other generators are set as group 2, and generator classification information D3 ′. May be created.

  Since most generators are accelerated during an accident, (δ1-δ0) representing the characteristics during the accident is a positive value. The B region on the two-dimensional coordinates is equal to or less than the average value during the accident, but includes a generator whose phase angle increases after the accident is removed, and the characteristics after the accident need to be taken into consideration.

  In the conventional grouping method, the region where (δ1−δ0) is positive (A + C) is an unstable generator. However, in this embodiment, the characteristics after the accident removal (δ2−δ0) are taken into account. A generator with a stable tendency can be created.

  Therefore, according to this embodiment, when the stability simulation is performed on a plurality of assumed accidents, the grouping of the generators corresponding to the assumed accidents is not a human judgment but represents the characteristics during the accident (δ1 -Δ0) and (δ2-δ0) representing the characteristics after accident removal are considered, and a grouping is automatically determined based on a calculation formula based on a predetermined threshold on the coordinates. can do. In addition, when grouping generators, it is determined in consideration of the accumulation of generator energy during an accident that causes the unstable phenomenon of the generator and the system state after the accident is removed. Appropriate grouping of machines can be performed.

(Fourth embodiment)
FIG. 10 is a diagram showing a process flow for explaining the fourth embodiment of the stability determination method of the power system according to the present invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As in the first embodiment, this power system stability determination method includes an initial state estimation input step 11, an assumed accident setting step 12, a stability simulation processing step 13, a two-system model creation step 14, a system admittance. In addition to the estimation step 15 and the stability determination evaluation step 16, the acceleration energy index and the deceleration energy index are newly calculated using the generator internal phase angular angular velocity immediately after the accident removal obtained in the stability simulation processing step 13, A two-dimensional energy index grouping processing step 41 for creating generator classification information D3 ′ based on these two energy indexes is provided.

  Also in the fourth embodiment, the basic processing flow for determining the stability of the power system is the same as that of the first embodiment, and in particular, the generator classification information is automatically generated based on a predetermined calculation formula. The difference is that D3 is created.

  Next, the operation of the power system stability determination method as described above will be described.

  In the stability simulation processing step 13, the behavior of the power system 1 is performed using the initial state quantity input from the initial state estimation input step 11 for each assumed accident set from the assumed accident setting step 12 as described above. (Transient stability), that is, the detailed stability of the power system 1 is calculated, and the stability calculation result D2 is obtained. The detailed description is as described based on the formulas (1) to (17).

  Therefore, in this embodiment, the generator internal phase angular angular velocity ω immediately after the accident is removed from the stability calculation result D2 obtained in the stability simulation processing step 13, and the acceleration energy during the accident and the deceleration energy after the accident is removed. The two indices are expressed two-dimensionally as an X axis and a Y axis, and the generators are grouped according to the following process.

First, acceleration energy stored in each generator in an accident is called AE (Acceleration Energy). This acceleration energy AE serves as an index representing the accident removal instantaneous state and can be represented by the following equation.

  Where Mi is the inertia constant of each generator, and Δωi is the angular deviation of each generator.

  In the equation (4-1), the first term on the right side is the acceleration energy of the generator, and the second term on the right side is the acceleration energy of the inertial central axis (virtual generator having the sum of inertia constants).

Here, the angular velocity deviation Δωi of each generator is approximated by the following formula, where ΔT is the accident duration, P0i is the generator active power output before the accident, and Pfi is the generator active power output at the time of the accident. Can be requested.
Δωi = {(P0i−Pfi) / Mi} ΔT (4-3)
Therefore, the AE of each generator becomes the following equation by combining the equations (4-1) to (4-3).

On the other hand, the deceleration energy of each generator after the accident is removed is called DE (Deceleration Energy). This deceleration energy DE is an index representing the state after the accident is removed. As in the case of the acceleration energy AE, if the inertia constant of the generator i is Mi, the generator active power output before the accident occurs is P0i, and the generator active power output at the moment of accident removal is Pci, The deceleration force Pdi of the generator can be expressed by the following equation.

  Further, when the acceleration energy AE during the accident and the deceleration energy DE after the accident removal are obtained as described above, the acceleration energy AE during the accident is the X axis, and the deceleration energy DE after the accident removal is the Y axis. The graph has two-dimensional coordinates. Then, the generators can be grouped by indicating the average value of each energy on the coordinates as a threshold value. That is, the generator classification information D3 ′ can be created by setting the generators larger than the X-axis threshold and larger than the Y-axis threshold to group 1 and the other generators to group 2.

  After generating the generator classification information D3 ′ based on a predetermined calculation formula in the two-dimensional energy index grouping processing step 41, in the two-system model creation step 14, the stability calculation result D2 and the generator classification information D3 ′ are obtained. To create an equivalent two-machine model. The processes after the two-system model creation step 14 are the same as those in the first embodiment, and will be described here.

  Therefore, according to the embodiment as described above, when the stability simulation is performed for a plurality of assumed accidents, the grouping of the generators corresponding to the assumed accidents is not a human judgment, but the acceleration energy during the accidents. And the deceleration energy after the accident removal is used as an index, the generator grouping can be determined. In addition, when grouping generators, it is determined in consideration of the acceleration energy of the generator during the accident, which causes the unstable phenomenon of the generator, and the deceleration energy of the generator after the accident is removed. The generator can be grouped appropriately.

(Fifth embodiment)
FIG. 11: is a figure which shows the process sequence explaining 5th Embodiment of the stability determination method of the electric power grid | system which concerns on this invention. In the figure, the same parts as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  As in the first embodiment, this power system stability determination method includes an initial state estimation input step 11, an assumed accident setting step 12, a stability simulation processing step 13, a two-system model creation step 14, a system admittance. An estimation step 15 and a stability discrimination evaluation step 16 are included.

  Furthermore, in this embodiment, a stability screening step 51 and a detailed stability verification step 52 are newly added to realize a process for increasing the reliability of further stability determination in the current system.

  The stability screening step 51 extracts an unstable case from the stability determination result D5 obtained in the stability determination evaluation step 16 in a plurality of assumed accident cases.

  The detailed stability verification step 52 performs all the stability calculations over the analysis target time for the unstable case extracted in the stability screening step 51, and extracts the stability determination result from the result.

Hereinafter, in this embodiment, the processing operation of the newly added part will be described.
In the stability discrimination evaluation step 16 in each embodiment described above, based on the estimated system parameter D4 and the detailed stability calculation result D2, the stability discrimination and the quantitative evaluation of stability using the extended equal area method, that is, The stability determination result D5 is extracted. The description of the operation relating to the stability determination evaluation process will be left to the description of the first embodiment.

  In the first embodiment, the value K serving as the stability index is obtained by the equation (56). However, in the stability screening step 51 according to the present embodiment, the value K serving as the stability index is negative. If the value is, it is considered unstable, and the corresponding accident is considered for calculation. In addition, when all the assumed accidents are determined to be stable, the corresponding assumed accidents are extracted as calculation targets for a predetermined number of cases (for example, 10 cases) in order from the smallest value of K. Send to stability verification step 52.

  In this detailed stability verification step 52, a stability simulation is performed for a predetermined time (for example, 5 seconds) for the assumed accident to be calculated, and the system behavior and the generator behavior are calculated. To do. Then, from this series of calculation results, it is verified whether the current system is stable or unstable, and a discrimination result is obtained.

  According to this embodiment, high-speed and simple stability determination is performed for a large number of assumed accidents, and detailed stability calculation is performed while focusing on accident cases that are clearly unstable. Stable determination can be performed with high speed and high reliability.

  Although the fifth embodiment has been described by applying to the first embodiment, it is needless to say that the fifth embodiment can be similarly applied to the second to fourth embodiments described above.

(Sixth embodiment)
FIG. 12 is a diagram showing a flow of processing for explaining the sixth embodiment of the power system stability determination method according to the present invention. In the figure, the same parts as those in FIG. 1 described in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In this power system stability determination method, the initial state estimation input step 11, the assumed accident setting step 12, the stability simulation processing step 13, the 2-machine model creation step 14 and the system admittance estimation step 15 are the same as those in the first embodiment. Is the same.

  In this embodiment, the difference is that, in place of the stability discrimination evaluation step 16 shown in FIG. 1, a post-reclosing curve approximation step 61 and a stability discrimination evaluation step 62 with a reclosing sequence are used.

  As described above, the stability determination evaluation step 16 in the first embodiment determines the stability of each generator in the assumed accident based on the P-δ curve (curve) shown in FIG. When the accident is an unbalanced accident, the P-δ curve changes from P1 to P2 as shown in FIG. 13 after the reclosing of the switch. In FIG. 13, δt indicates a phase angle when the reclosing is performed. That is, the P-δ curve changes to another curve due to the reclosing of the switch.

  As a result, when the P-δ curve is switched during the reclosing operation, the stability determination evaluation step 16 cannot calculate DCC (deceleration energy) using the equation (55).

  Therefore, in this embodiment, instead of the stability determination evaluation step 16, the stability determination is performed using the post-reclosing curve approximation step 61 and the stability determination evaluation step 62 with the reclosing sequence. The post-reclosing curve approximation step 61 refers to the assumed accident data D1 stored in the database 3 and acquires the assumed accident information in the above case.

  Then, after the reclosing curve approximation step 61, if the assumed accident is an equilibrium accident, the stability determination is performed by calculating DCC using the same method as the stability determination evaluation step 16, that is, the equation (55). If the assumed accident is an unbalanced accident, the curve P2 after reclosing the switch shown in FIG. 13 is estimated. Now, assuming that the reclosing time of the switch in the stability simulation processing step 13 is 0.5 seconds and the step size is 0.01 seconds, the P-δ curve after the reclosing is estimated as follows. In estimating the curve approximation, it is assumed that Pc does not change before and after reclosing, and ν does not change before and after reclosing.

Before reclosing: Curve P1 = Pc + P1 _max sin (δ + ν) (61)
After reclosing: Curve P2 = Pc + P2 _max sin (δ + ν) (62)
Here, after replacing equation (62) with P2 _max = (P2−Pc) / sin (δ + ν), substituting equation (61) to eliminate sin,
_P2max = (P2-Pc) / {(P1-Pc) / _P1max }
= P1 _max (P2-Pc) / (P1-Pc).
Here, paying attention to before and after reclosing,
P2 _max = P1 _max (P (0.50 seconds) −Pc) / (P (0.49 seconds) −Pc).

Therefore, the post-reclosing curve approximation step 61 estimates the P-δ curve after the reclosing as described above, and then proceeds to the stability determination and evaluation step 62 with a reclosing sequence, where the DCC is calculated based on the following equation. Is calculated.

  Here, in the equation (63-2), ta is a time immediately before reclosing, and tb is a time immediately after reclosing.

That is, the DCC can be calculated by finally deriving the equation (63-2) based on the equation (63-1). Here, P1 _max and P2 _max are as described above.

  Therefore, according to the embodiment as described above, when the assumed accident is an unbalanced accident, even if the P-δ curve changes to a different curve from that before the reclosing after the reclosing, the highly accurate DCC (Deceleration energy) can be calculated.

  In the sixth embodiment, an example in which a post-reclosing curve approximation step 61 and a stability determination evaluation step 62 with a reclosing sequence are applied in place of the stability determination evaluation step 16 of the first embodiment will be described. However, it goes without saying that the present invention can be similarly applied to the second to fifth embodiments described above and the seventh and eighth embodiments described later.

(Seventh embodiment)
FIG. 14 is a diagram showing a flow of processing for explaining a seventh embodiment of the power system stability determination method according to the present invention. In the figure, the same parts as those in FIG. 7 described in the third embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As in the third embodiment, this power system stability determination method is performed by an initial state estimation input step 11, an assumed accident setting step 12, a stability simulation processing step 13, a two-system model creation step 14, a system admittance. In addition to the estimation step 15, the stability discrimination evaluation step 16 and the two-dimensional phase angle grouping processing step 32, the impedance of the assumed accident target transmission line is increased in place of the post-accident generator internal phase angle calculation step 31 shown in FIG. A simple impedance flow calculation step 71 for performing the flow calculation is provided.

  In the seventh embodiment, the basic processing flow for determining the stability of the power system is the same as that of the third embodiment. A particularly different point is that instead of the post-accident generator internal phase angle calculation step 31 shown in FIG. 7 for explaining the third embodiment, a simple impedance flow calculation step 71 is provided. In the calculation, the difference is that the tidal current calculation is performed with the impedance of the transmission line subject to the assumed accident increased.

  Furthermore, it demonstrates concretely. In the third embodiment, the instability phenomenon of the generator is greatly affected by two factors, that is, energy accumulation in the generator during the accident and the system state after the accident is removed. Therefore, when considering these factors, attention is paid to the following three phase angles.

(1) Generator internal phase angle D31 (δ0) of the initial power system: internal phase angle in the initial state
(2) Generator internal phase angle D33 (δ1) immediately after the accident is removed: Internal phase angle immediately after the accident is removed in the detailed stability calculation
(3) Generator internal phase angle D32 (δ2) of the post-accident system: This is an internal phase angle obtained by tidal current calculation and initial value calculation of the post-accident system.

  In the third embodiment, the generator internal phase angle calculation step 31 after the accident removal performs the tidal current calculation using the assumed accident data D1 obtained from the assumed accident setting step 12 according to (3) above. Δ2i which is the internal phase angle D32 of the system after the assumed accident is obtained. At this time, depending on the assumed accident, the power flow calculation may not be converged. The fact that the power flow calculation after the assumed accident does not converge means that the stability is severe, and it can be determined that the stability determination is not performed without performing the stability determination evaluation step 16. However, as a result, the stability determination index value K cannot be calculated, and quantitative stability determination becomes impossible.

  Therefore, in this embodiment, instead of the generator internal phase angle calculation step 31 after the accident removal, the simple impedance flow calculation step 71 is used to increase the impedance of the assumed accident target transmission line and perform the flow calculation.

  In general, it is possible to simulate the impedance infinite by opening the transmission line, but in this embodiment, the impedance of the transmission line is a size that can be converged by power flow calculation (5 to 10 times) The tide calculation is performed to obtain δ2i. In this case, the accuracy of δ2i is somewhat reduced, but it can be used without any problem because it is used for comparison with other assumed accidents.

  In the present embodiment, the simple impedance flow calculation is similarly applied to the extraction of δ1i from the stability calculation result D2 performed by the post-accident generator internal phase angle calculation step 31 in the third embodiment. This is performed in step 71.

  Therefore, according to this embodiment, it is possible to reliably calculate δ2i by providing means for converging the tidal current calculation even in a severe assumed accident in which the tidal current calculation in the steady state after the accident removal is not yet converged. Can do. As a result, it is possible to determine the stability from other assumed accidents using the above-described stability determination index value K.

(Eighth embodiment)
FIG. 15 is a diagram showing a flow of processing for explaining an eighth embodiment of the power system stability determination method according to the present invention. In the figure, the same parts as those in FIG. 7 described in the third embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  As in the third embodiment, this power system stability determination method is performed by an initial state estimation input step 11, an assumed accident setting step 12, a stability simulation processing step 13, a two-system model creation step 14, a system admittance. In addition to the estimation step 15, the stability discrimination evaluation step 16 and the two-dimensional phase angle grouping processing step 32, a detailed stability simulation is performed from the stability calculation result D2 instead of the post-accident generator internal phase angle calculation step 31 shown in FIG. A generator internal phase angle extraction step 81 for extracting the internal phase angle D33 of each generator at δ2i at the time tx of calculation is provided.

  In the eighth embodiment, the basic processing flow for determining the stability of the power system is the same as that of the third embodiment. The difference is that, in the third embodiment, the generator internal phase angle calculation step 31 after the accident removal, instead of calculating the power flow and calculating the internal phase angle D32 δ2i, the generator internal phase angle is extracted. Step 81 differs from the stability calculation result D2 in that the internal phase angle D33 of each generator at the time tx of calculation of the detailed stability simulation is taken out as δ2i and sent to the two-dimensional phase angle grouping processing step 32.

  Furthermore, it demonstrates concretely. As described above, the instability phenomenon of the generator is greatly influenced by two factors such as energy accumulation in the generator during the accident and the system state after the accident is removed. Therefore, when these factors are considered, attention is paid to the following three phase angles as described above.

(1) Generator internal phase angle D31 (δ0) of the initial power system: internal phase angle in the initial state
(2) Generator internal phase angle D33 (δ1) immediately after the accident is removed: Internal phase angle immediately after the accident is removed in the detailed stability calculation
(3) Generator internal phase angle D32 (δ2) of the post-accident system: This is an internal phase angle obtained by tidal current calculation and initial value calculation of the post-accident system.

  In the third embodiment, after the accident removal, the generator internal phase angle calculation step 31 performs the tidal current calculation using the assumed accident data D1 obtained from the assumed accident setting step 12 based on the above (3). Δ2i which is the internal phase angle D32 of the system after the assumed accident of the machine is obtained. At this time, depending on the assumed accident, the power flow calculation may not be converged. The fact that the power flow calculation after the assumed accident does not converge means that the stability is severe, and it can be determined that the stability determination is not performed without performing the stability determination evaluation step 16. However, as a result, the stability determination index value K cannot be calculated, and quantitative stability determination becomes impossible.

  Therefore, in the present embodiment, instead of the generator internal phase angle calculation step 31 after the accident removal, the generator internal phase angle extraction step 81 includes, in the stability calculation result D2, each power generation at the calculation termination time tx of the detailed stability simulation. The internal phase angle D33 of the machine is extracted as δ2i and sent to the two-dimensional phase angle grouping processing step S32. At the time tx when the detailed stability simulation is terminated, the phase angle reflecting the system state after the accident is removed is obtained, so that it can be applied as δ2i.

  In the present embodiment, similarly to the extraction of δ1i from the stability calculation result D2 performed in the post-accident generator internal phase angle calculation step 31 in the third embodiment, the internal phase angle of the generator This is performed in the taking out step 81.

  Therefore, according to this embodiment, it is possible to calculate δ2i by providing means for converging the tidal current calculation even in a severe assumed accident in which the tidal current calculation in the steady state after the accident removal is unconverged. It becomes. As a result, it is possible to determine the stability from other assumed accidents using the above-described stability determination index value K.

  In addition, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the invention.

The figure which shows the flow of the process explaining 1st Embodiment of the stability determination method of the electric power grid | system which concerns on this invention. The figure explaining an example of the generator classification | category information shown in FIG. The figure which shows the 2 machine type | system | group equivalent model created using the stability simulation implementation result and generator classification information. The P-delta curve figure explaining the extended equal area method used with the method of this invention. The figure which shows the flow of a process explaining 2nd Embodiment of the stability determination method of the electric power system which concerns on this invention. The figure which shows the 2 machine type | system | group equivalent model created using the stability simulation implementation result and generator classification information. The figure which shows the flow of a process explaining 3rd Embodiment of the stability determination method of the electric power grid | system which concerns on this invention. The figure explaining an example of the two-dimensional phase angle grouping process step shown in FIG. The figure explaining the other example of the two-dimensional phase angle grouping process step shown in FIG. The figure which shows the flow of a process explaining 4th Embodiment of the stability determination method of the electric power grid | system which concerns on this invention. The figure which shows the flow of a process explaining 4th Embodiment of the stability determination method of the electric power grid | system which concerns on this invention. The figure which shows the flow of a process explaining 6th Embodiment of the stability determination method of the electric power grid | system which concerns on this invention. The figure explaining the DCC calculation method at the time of the P-delta curve switching method by the reclosing method and the approximation method of the P-delta curve after the reclosing of the switch. The figure which shows the flow of a process explaining 7th Embodiment of the stability determination method of the electric power grid | system which concerns on this invention. The figure which shows the flow of a process explaining 8th Embodiment of the stability determination method of the electric power grid | system which concerns on this invention. The figure which shows the flow of a process in the stability determination method of the conventional electric power system.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Electric power system, 2 ... Stability discrimination | determination processing apparatus, 11 ... Initial state estimation input step, 12 ... Assumed accident setting step, 13 ... Stability simulation processing step, 14 ... Two system model creation step, 15 ... System admittance estimation Step: 16 ... Stability discrimination evaluation step, 21 ... Two-machine simple model creation step, 22 ... System parameter estimation step, 31 ... Generator internal phase angle calculation step after accident removal, 32 ... Two-dimensional phase angle grouping processing step, 41 ... Two-dimensional energy index grouping processing step, 51 ... Stability screening step, 52 ... Detailed stability verification step, 61 ... Post-reclosing curve approximation step, 62 ... Stability discrimination evaluation step with reclosing sequence, 71 ... Simple impedance flow calculation step , 81 ... Generator internal phase angle extraction Step, D1 ... Assumed accident data, D2 ... Stability calculation result, D3, D3 '... Generator classification information, D4 ... System parameter (admittance), D5 ... Stability discrimination result, D21 ... System parameter (product of admittance and voltage) , D31 ... Generator internal phase angle in the initial state, D32 ... Generator internal phase angle after assumed accident system, D33 ... Generator internal phase angle after accident removal.

Claims (9)

In the power system transient stability determination method for determining the transient stability of the power system to which a plurality of generators are connected,
An initial state estimation input step for estimating and calculating the most probable initial state of the power system to be determined for the transient stability;
An assumed accident setting step for setting an assumed accident with respect to the initial state of the power system;
Stability simulation processing step for calculating the detailed stability of the power system using the initial state input from the initial state estimation input step for each assumed accident set from the assumed accident setting step;
Based on the generator internal voltage vector and the generator active power output, which are part of the stability calculation result obtained in this stability simulation processing step, and the preset generator classification information, an equivalent two-system model is obtained. 2-machine model creation step to create,
A system admittance estimation step for estimating an equivalent system admittance between the two reduced generators constituting the two-system model created in the creation step;
A stability discrimination evaluation step for obtaining a stability discrimination result such as stability discrimination and quantitative evaluation of stability by the extended equal area method based on the system admittance estimated in the estimation step and the stability calculation result. A method for determining the transient stability of the power system. In the method for determining the transient stability of the electric power system according to claim 1,
Instead of the two-machine model creation step, the generator internal voltage vector, which is a part of the stability calculation result obtained in the stability simulation processing step, is simplified by a predetermined method and the generator active power. Using a 2-machine simple model creation step for creating an equivalent 2-machine model based on the output and preset generator classification information,
Further, instead of the system admittance estimation step, an equivalent system admittance between the two reduced generators constituting the two-system model created in the two-system simple model creation step and the generator internal voltage A method for determining the transient stability of a power system, wherein a system parameter estimation step for estimating a system parameter from a product of the system is used. In the transient stability determination method of the electric power system according to claim 1 or claim 2,
As the setting process of the generator classification information, for each assumed accident set in the assumed accident setting step, a stability calculation is performed to calculate the internal phase angle of the system after removing the assumed accident of each generator. The initial state of the electric power system with respect to the electric machine internal phase angle calculation step, the internal phase angle of the generator after the assumed accident removal and the internal phase angle immediately after the accident removal of each generator obtained by the stability simulation processing step The phase angle deviation of the generator internal phase angle is set to the X axis and the Y axis, respectively, and the average value taking into account the generator unit inertia constant belonging to each phase angle deviation is set to the threshold of the X axis and the threshold of the Y axis. And a two-dimensional phase angle grouping processing step for grouping the generators by setting the value to a value. In the transient stability determination method of the electric power system according to claim 1 or claim 2,
As the generator classification information setting process, the acceleration energy and deceleration energy at the time of the accident obtained from the internal phase angle angular velocity immediately after the accident removal of each generator obtained by the stability simulation processing step are respectively set to the X axis and the Y axis. And a two-dimensional energy index grouping processing step for performing grouping of each generator. In the transient stability determination method of the electric power system as described in any one of Claims 1 thru | or 4,
A stability screening step for extracting unstable accident cases based on stability determination results obtained by the stability determination evaluation step for a plurality of assumed accident cases, and the stability simulation processing step for the unstable accident cases extracted in this step. A method for determining the transient stability of a power system, characterized in that a stability simulation is performed within a predetermined analysis target time range and a detailed stability verification step for verifying stability and instability in the current system is added. In the method for determining the transient stability of the electric power system according to claim 1,
Instead of the stability discrimination evaluation step, when the assumed accident causes the re-closing of the switch due to an unbalanced accident, the P-δ curve before the re-closing is changed from the P-δ curve before the re-closing to the P-δ curve after the re-closing. When switching, the post-reclosing curve approximation step for estimating the post-reclosing P-δ curve, and the system admittance and the stability estimated in the system admittance estimation step separately before and after the switching of the P-δ curve A power system transient stability determination method, comprising: a stability determination step with a reclosing sequence that calculates deceleration energy based on a calculation result, and performs stability determination and quantitative evaluation of stability. In the method for determining the transient stability of the electric power system according to claim 3,
Instead of the step of calculating the internal phase angle of the generator after removing the accident, if the power flow calculation has not converged according to the assumed accident, the impedance of the target transmission line of the assumed accident is set to a size that can be virtually converged. A method of determining transient stability of a power system, comprising a simple impedance power flow calculation step for calculating a power flow and obtaining a generator internal phase angle of the system after an assumed accident. In the method for determining the transient stability of the electric power system according to claim 3,
Instead of the step of calculating the internal phase angle of the generator after removing the accident, the internal phase angle of each generator at the time of the calculation termination of the detailed stability simulation is used as the generator internal phase angle of the post-accident system. A method for determining transient stability of an electric power system, comprising a step of extracting a generator internal phase angle to be substituted. In the power system transient stability determination device for determining the transient stability of the power system to which a plurality of generators are connected,
Initial state estimation input means for estimating and calculating the most probable initial state of the power system to be subjected to the determination of the transient stability;
Assumed accident setting means for setting an assumed accident for the initial state of the power system;
Stability simulation processing means for calculating the detailed stability of the power system using the initial state input from the initial state estimation input means for each assumed accident set from the assumed accident setting means,
Based on the generator internal voltage vector and the generator active power output, which are a part of the stability calculation result obtained by the stability simulation processing means, and the preset generator classification information, an equivalent two-system model is obtained. 2-machine model creation means to create,
System admittance estimation means for estimating an equivalent system admittance between the two reduced generators constituting the two-system model created by the creation means;
Stability discrimination evaluation means for obtaining stability discrimination results such as stability discrimination and quantitative evaluation of stability by the extended equal area method based on the system admittance estimated by the estimation means and the stability calculation result A power system transient stability discrimination device.

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