CN107611996A - The centralized positioning of multi-frequency oscillation asynchronous oscillation and migration tracing system and its method - Google Patents
The centralized positioning of multi-frequency oscillation asynchronous oscillation and migration tracing system and its method Download PDFInfo
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Abstract
The invention belongs to Power System Stability Analysis technical field, more particularly to a kind of centralized positioning of multi-frequency oscillation asynchronous oscillation and migration tracing system and its method based on position function, any is connected in build three machine equivalence system models by three-line with three side power supplys；The voltage vector expression formula at any point in the case where three side power supplys act on simultaneously is obtained according to superposition theorem；Oscillation center position function is set according to line impedance ratio；Quadratic function is expanded into after the voltage vector expression formula at any point is rewritten into the form of modulus value and phase, asks for obtaining after partial derivative the expression formula of any side oscillation center position further according to trigonometric function relation and average inequality；Analysis system is with respect to the influence of generator rotor angle, impedance structure parameter, system power source voltage amplitude these three factors to oscillation center, obtain each side and the condition of out-of-step center occur, the later position for determining out-of-step center of criterion is obtained according to the trigonometric function relation of voltage vector.
Description
Technical Field
The invention belongs to the technical field of stability analysis of power systems, and particularly relates to a multi-frequency oscillation out-of-step oscillation center positioning and migration tracking system and method based on a position function.
Background
With the development of ultrahigh voltage interconnected power grids and the access of a large amount of new energy in China, the scale of a power system is gradually enlarged, the operation mode of the system is changeable, and the possibility that the system is disturbed to oscillate and cause a large-range power failure accident is also sharply increased. Meanwhile, the system oscillation presents the characteristics of complex cause, variable modes and the like, and the oscillation center may not be on a certain fixed line but may dynamically migrate on different lines, thereby bringing a serious challenge to the oscillation identification of the safety and stability device of the power system.
At present, the analysis and research of the oscillation characteristics at home and abroad are mostly based on two-machine system models, and the analysis methods mainly comprise three types: based on voltage current or impedance trajectory variation characteristics, based on frequency distribution characteristics, and based on energy or power, etc. However, in a multi-frequency oscillation scene, the analysis method based on the two-machine model is not applicable any more, and the oscillation characteristics obtained based on the two-machine model are difficult to describe the actual situation of multi-frequency oscillation. Out-of-step oscillation center positioning methods in a multi-frequency oscillation scene are rarely reported.
Disclosure of Invention
In order to solve the technical problems, the invention provides a multi-frequency oscillation out-of-step oscillation center positioning and migration tracking system and a method thereof based on a position function.
The system comprises a system information acquisition module, an oscillation center position migration tracking module, an out-of-step center positioning module and an out-of-step oscillation center position output module which are sequentially connected; the system information acquisition module is used for acquiring system structural parameters, power angles, rotating speeds and voltage amplitudes of generators on all sides of the system and sending acquired data to the step-out center positioning module; the oscillation center position migration tracking module calculates the oscillation center position of each side of the system by using the information acquired by the information acquisition module, so that the tracking and analysis of the drift path of the oscillation center of the multi-frequency oscillation system are realized; the step-out center positioning module is used for positioning the position of a step-out center in the system according to the provided step-out center positioning criterion; and the step-out oscillation center position output module is used for outputting a step-out center position and an oscillation center drift path.
The method comprises the following steps:
step 1: three side power supplies are connected to one point through three lines to construct a three-machine equivalent system model;
step 2: obtaining a voltage vector expression of any point under the simultaneous action of the three side power supplies according to the superposition theorem;
and step 3: setting an oscillation center position function according to the line impedance ratio; rewriting a voltage vector expression of any point into a mode value and phase form, expanding the mode value and phase form into a quadratic function, calculating a partial derivative, and then obtaining an expression of the oscillation center position of any side according to a trigonometric function relation and a mean value inequality;
and 4, step 4: analyzing the influence of three factors of a system relative power angle, impedance structure parameters and system power supply voltage amplitude on an oscillation center, obtaining the condition of the occurrence of the step-out center on each side, and determining the position of the step-out center after obtaining a criterion according to the trigonometric function relation of voltage vectors.
The voltage vector expression is expressed by taking the side A as the following:
in the formula (I), the compound is shown in the specification,is the voltage vector at any point p in the a-side line,is the equivalent potential of an A-side system, p is the distance from any point rho to a bus A, and delta 12 And delta 13 Respectively equal potential of B side systemEquivalent potential of A side systemEquivalent potential of C-side systemEquivalent potential of A side systemThe phase angle difference between the two phases is small,is the voltage amplitude ratio of the equivalent potential of the B-side system to the equivalent potential of the A-side system,the voltage amplitude ratio of the equivalent potential of the C-side system to the equivalent potential of the A-side system, the intermediate variableIntermediate variablesZ AΣ ＝Z A +Z AO ，Z BΣ ＝Z B +Z BO ，Z CΣ ＝Z C +Z CO ，Z AΣ 、Z BΣ 、Z CΣ Respectively representing the combined impedance of the A-side, B-side and C-side systems, Z A 、Z B 、Z C Respectively represent the equivalent power source impedance of the system at the A side, the B side and the C side, Z AO 、Z BO 、Z CO Equal impedance of A, B, C three-side line.
The expression of the oscillation center position on any side is expressed with side a as, for example:
i may take A, B, C, f i (δ) represents the function of the position of the oscillation center on the A, B, C side, taking i as A for example,S 2 and S 1 The quadratic and the first order coefficient respectively of the voltage magnitude factor of the system for the position p,
the conditions for the occurrence of the out-of-step center on each side are as follows:
wherein the coefficient k may be [0, + ∞ [ ]]Any value in the range between (a) and (b),three lines are connected with the voltage phasor of the point O,intermediate variables
The criterion comprises a main criterion 1, a main criterion 2 and an auxiliary criterion, wherein the main criterion 1 is as follows:
wherein epsilon is a protection action judgment threshold; the main criterion 2 is:
the auxiliary criterion is:
wherein k is the ratio of the voltage at the point O to the electromotive force amplitude of the generator at each side; when the owner judgesThe next calculation can be carried out according to any one of the conditions 1 and the main criterion 2; if the out-of-step center is in the A side system, it is also necessary to consider k e [0, + ∞]I.e. byIf the main criterion and the auxiliary criterion are met simultaneously, the step-out center is in the A-side system, and the position of the step-out center is as follows:
in the formula, p 0 Representing the ratio of the impedance distance between the step-out center and the A-side system to the comprehensive impedance of the A-side system, and finally obtaining the position function of the step-out center:
the invention has the beneficial effects that: aiming at the technical problem that multi-frequency oscillation is difficult to describe based on oscillation characteristics obtained by a two-machine model in a multi-frequency oscillation scene, a multi-frequency oscillation step-out oscillation center positioning and migration tracking system based on a position function, a multi-frequency oscillation step-out oscillation center positioning and migration tracking method and a multi-frequency oscillation step-out oscillation center positioning and migration tracking method are provided, an expression of voltage and current in the multi-frequency oscillation scene is obtained, then a step-out center position function and an oscillation center position function are constructed according to the definition of an oscillation center and a step-out center, positioning criteria of the step-out center in the multi-frequency oscillation scene are obtained, and positioning of the step-out center is achieved. The simulation result of the equivalent model of the multi-machine system verifies the correctness and effectiveness of the criterion and the tracking of the oscillation center of the method.
Drawings
Fig. 1 is a structural diagram of a system for locating and migrating tracking a center of a multi-frequency oscillation out-of-step oscillation based on a position function according to the present invention.
Fig. 2 is a schematic diagram of a three-machine system model in an embodiment of the invention.
Fig. 3 is a voltage phasor diagram when an a-side step-out center occurs in the embodiment of the present invention.
FIG. 4 is a graph of the amplitude and position of the oscillation center voltage over time in an embodiment of the present invention.
Fig. 5 is a graph showing the variation of the amplitude and position of the oscillation center voltage with time in different oscillation modes according to the embodiment of the present invention.
Fig. 6 is a graph showing the change of the amplitude and position of the oscillation center voltage with time when the impedance parameter is changed according to the embodiment of the present invention.
Fig. 7 is a graph showing the change of the amplitude and position of the oscillation center voltage with time when the impedance parameter is changed according to the embodiment of the present invention.
Fig. 8 is a graph showing the change in the position of the oscillation center voltage in the case of different potential amplitude ratios in the embodiment of the present invention.
Detailed Description
The embodiments are described in detail below with reference to the accompanying drawings.
Fig. 1 is a structural diagram of a multi-frequency oscillation out-of-step oscillation center positioning and migration tracking system based on a position function, which includes a system information acquisition module, an oscillation center position migration tracking module, an out-of-step center positioning module and an out-of-step oscillation center position output module that are connected in sequence.
Fig. 2 is a schematic diagram of a model of a three-machine system, in fig. 2,equal potential of the system is respectively bus R, bus S and bus T, delta 1 、δ 2 、δ 3 Respectively corresponding equivalent power angle, Z A 、Z B 、Z C Respectively corresponding equivalent power supply impedances. Z is a linear or branched member AO 、Z BO And Z CO Equal impedances of the lines RO, SO, TO, respectively. In the analysis process, the bus flow direction line is taken as the positive direction of the current, the impedance value is unchanged within the frequency range, and the impedance angles of the upper-level element and the lower-level element of the system are equal.
The current of any point in the system can be calculated by using a superposition theorem, and the current flowing on the line is the sum of the currents flowing when the three power supplies act independently. Taking side a as an example, consider the case where side a power supply 1 alone is acting:
in the formula: z AΣ ＝Z A +Z AO ，Z BΣ ＝Z B +Z BO ，Z CΣ ＝Z C +Z CO The impedance values represent the combined impedance of the a-side, B-side, and C-side systems, respectively.
Similarly, the expression of the a-side current when only the B-side power supply 2 alone is considered and when the C-side power supply 3 alone is considered can be obtained as:
when three power supplies in the system act simultaneously, the current expression of the A side obtained by applying the superposition theorem is as follows:
from equation (3), the voltage at any point in the system can be calculated. Taking side A as an example, let us say that any point ρ on the line AO, the distance from the point to the bus AWherein Z Aρ The equivalent impedance value from the system A to the rho point, the voltage expression of the point is as follows:
in the formula: p is more than or equal to 0 and less than or equal to 1,is the voltage phasor at the ρ point.
The formula (3) may be substituted for the formula (4):
in the formula (5), theWith the a-side equivalent power supply potential as a reference, equation (5) can be rewritten as:
in the formula, delta 12 And delta 13 Are respectively an electric potentialAnd electric potentialElectric potentialAnd electric potentialThe phase angle difference between them, i.e.: delta 12 ＝δ 2 -δ 1 ，δ 13 ＝δ 3 -δ 1 ，Is the voltage amplitude ratio of the equivalent potential of the B-side system to the equivalent potential of the A-side system,the voltage amplitude ratio of the equivalent potential of the C-side system to the equivalent potential of the A-side system is obtained.
Tracking of the migration of the oscillation center:
the oscillation center is a point where the voltage amplitude in the system drops to the lowest in a certain oscillation mode. But since the determination of the center of oscillation serves the automation in the system, for a certain system-side protection or disconnection device, the meaning of the center of oscillation should be further defined as a voltage sag condition within the device's perceptible range. Therefore, the system side oscillation center is defined as the lowest voltage point in the comprehensive impedance range of the system on the side under a certain oscillation mode. Let the oscillation centers on the A, B, C side in FIG. 2 be D A 、D B 、D C The corresponding oscillation center position function can be defined as:
in the formula:the impedance values of the A-side, B-side and C-side systems to the oscillation center of the side, f A (δ)、f B (δ)、f C (δ) is a function of the position of the oscillation center on the A side, a function of the position of the oscillation center on the B side, and a function of the position of the oscillation center on the C side, respectively.
In order to facilitate the analysis of the voltage amplitudes of all points, the square of the voltage amplitude of the rho point at any point on the A side is defined as a voltage amplitude factor SF on the A side A Then its voltage expression (6) can be rewritten into the form of modulus and phase as follows:
in the formula:is a voltage magnitude coefficient of the rho point,is the equivalent initial phase angle of the phase-locked loop,
an expression for the voltage magnitude factor can be obtained from equation (6):
from the formula (9), SF A Is a function of the power angle difference, the voltage amplitude ratio and the position parameter p of the other side equivalent power supply relative to the A side power supply.
Expanding equation (9) as a quadratic function with respect to p can result:
SF A ＝S 2 p 2 -S 1 p+1 (10)
in the formula: s 2 And S 1 The quadratic coefficient and the first order coefficient of the voltage amplitude factor of the system for the position p are respectively expressed as follows:
finding SF in the formula (10) A Partial derivatives with respect to the position parameter p:
in the formula (I), the compound is shown in the specification,indicating that the partial derivative is taken of the parameter.
Derived from trigonometric relationships and mean inequalities, S 2 It is always true that 0 or more is used. Therefore, whenWhen is SF A There is a minimum value, the voltage is lowest. At this time corresponding to p 1A Namely an A-side oscillation center position expression:
from the above analysis, at a certain time, in a certain oscillation mode, there exists only one voltage lowest point in one side system, namely: the side (the cross section) oscillation center has uniqueness. p is a radical of 1A &1, the lowest voltage point of the line is positioned at the point O, and the oscillation center of the system is not positioned on the line; p is a radical of 1A &0, the oscillation center is positioned at the back side of the system, and the oscillation center of the system is not positioned on the line; 0<p 1A &And lt 1 the oscillation center of the circuit is positioned inside the circuit. Accordingly, the functional expression of the oscillation center position of each side can be written as follows:
in the formula, i may be A, B, C, which respectively represent A, B, C side oscillation center position function expressions.
The value of the oscillation center voltage is an important criterion for determining the stability of the system, and the value of p = f (δ) is substituted into equation (14) to obtain an oscillation center voltage factor expression:
from the expressions (13) to (14) of the oscillation center position, the oscillation center position is determined by the relative power angle of the system, the impedance structure parameter and the amplitude ratio of the power supply voltage of the system. The influence of the three factors on the oscillation center is analyzed respectively, and the system potential amplitude is assumed to be equal, namely k 12 ＝k 13 =1, the first two factors are analyzed and then the case of unequal amplitudes is analyzed. Considering the potential amplitudes to be equal, the oscillation center position expression is:
positioning the step-out center:
the step-out center is: in a certain oscillation mode, the voltage drops to a point of zero in the system at a certain moment. In an equivalent two-machine system with uniform impedance, the step-out center occurs when the system potential phase angle differs by 180 °. Because the currents of all points in the A-side system are equal in oscillation, if a step-out center appears in the A-side system, the phase angle between the potential of the A-side system and the voltage of the O point is 180 degrees. The same applies to the other sides. The conditions under which the out-of-step center occurs on each side can be found by combining formula (2):
wherein k may be [0, + ∞ [ ]]Any value in the range between (a) and (b),the O point voltage phasor can be obtained from the equation (6)The expression of (a) is:
in the formula (I), the compound is shown in the specification,
when the potential of any side in the system meets the criterion in the formula (17), the step-out center exists in the side system. However, since tracking and positioning of the step-out center are difficult to achieve by this equation, taking side a as an example, when the step-out center occurs, equation (18) can be rewritten as follows:
voltage phasor when equation (17) holdsAnd phasorThe phase difference is 180 deg., and the voltage phasor diagram at this time is shown in fig. 3, in which the phasorsEach representsThe sum of the three isPhasorsIs phasorPhasorsAnd (4) the sum. Also, considering the magnitude of the a-side system potential as 1, from figure 3,∠DOB＝π-δ 12 sum < ODB = δ 13 - π. According to the trigonometric function relationship, the conditions for the occurrence of the step-out center are as follows:
wherein epsilon is a protection action judgment threshold. The formula (20) is the main criterion 1. When δ is equal to 12 And delta 13 When the values of (d) are integer multiples of pi, the denominators on both sides of the equation in equation (20) are zero and cannot be calculated, or the values on both sides are infinite. In this case, three systems are electrically connectedThe potentials are on a straight line and need to be illustrated in two cases:
a) If delta 12 And delta 13 If the value of (a) is not an integer multiple of 2 pi, then there must be at least one side potentialConversely, there is at least one out-of-sync center in the system. In particular, when delta 12 And delta 13 Are all odd multiples of pi and k 13 k AB +k 12 k AC <k BC When the temperature of the water is higher than the set temperature,simultaneously withIn the opposite direction, the two out-of-step centers exist in the system on both the B side and the C side, namely the two out-of-step centers exist in the system. At this time, since the boundary value defined by equation (16) is greater than 1, neither the oscillation center nor the step-out center occurs in the a-side system.
b) If delta 12 And delta 13 The values of (2) are integral multiples of 2 pi, and the formula (3) shows that the current in the system is zero and no step-out center exists. At this time, the out-of-step centering is not necessary.
In summary, the main criterion 2 needs to be considered as follows:
and if the main criterion 1 and the main criterion 2 meet one of the two criteria, the next calculation can be carried out. If the out-of-step center falls within the A-side system, it is also necessary to consider k ∈ [0, + ∞]I.e. byTherefore, the auxiliary criterion is added as follows:
wherein k is the ratio of the voltage at point O to the electromotive force amplitude of the generator at each side. If the main criterion and the auxiliary criterion are met simultaneously, the step-out center is in the system on the side A, and the step-out center is positioned as follows:
in the formula, p 0 And the ratio of the impedance distance from the step-out center to the A-side system to the comprehensive impedance of the A-side system is represented.
By substituting the expression of k in equation (22) into equation (23), the function of the position of the step-out center can be obtained:
as can be seen from equation (24), there may be a plurality of step-out centers in the system, and the step-out centers migrate at different positions in the system as the power angle changes. The moment when the out-of-sync center exists can be seen approximately as the wobble of the combination of the two systems relative to the other system. However, since the power angle is continuously changed, the situation of short-time recombination of different systems is presented, and the combination rule is determined by the magnitude and sign of the relative angular velocity. Tracking and monitoring of the out-of-step center can be achieved according to equation (24), and similar deductions can be made on the other two sides. It is noted that the out-of-step center is the oscillation center at a particular time, and therefore, the boundary of the oscillation center is also the boundary of the out-of-step center migration, and in accordance with the oscillation center situation, there is only one out-of-step center in the system at most at a certain time.
In order to verify whether the method provided by the invention is correct under the conditions of different oscillation modes, different impedance parameters and different voltage amplitude ratios, a model shown in figure 2 is built by utilizing PSCAD, and in a basic simulation model, the potential amplitudes of three side power supplies are considered to be equal (k is considered to be equal) 12 ＝1，k 13 ＝1)，Andrespectively at Δ ω 12 =3 °/s and Δ ω 13 Relative angular velocity of =5 °/s aroundIn rotation, the system impedance parameters are: z is a linear or branched member AΣ ＝100∠86.5°Ω，Z BΣ ＝60∠86.5°Ω，Z CΣ ＝50∠86.5°Ω。
In the oscillation process, the oscillation center position and the oscillation center voltage amplitude of each side are shown in fig. 4, in which curve 1 represents the value of the oscillation center position function of each side and curve 2 represents the oscillation center voltage amplitude. As can be seen from fig. 4, the oscillation centers on the respective sides move toward the inside of the line from the point O and return after reaching the minimum value, and taking the side a as an example, the oscillation center minimum value returns after reaching the minimum value 0.6364.
The oscillation center of each side is shifted from the point O to the inside of the circuit, returns to the point O after reaching the farthest position, and then shifts to other sides. During the oscillation center migration, there may be an overlap, namely: when the oscillation center of one line moves from inside the line to point O, the oscillation center of the other line has already started to move from point O to inside the line thereof. At this time, the oscillation center of the system takes the point with the smaller voltage in the two points, and under the oscillation scene in this section, the oscillation center of the system sequentially drifts from L1 to L2 and L3. In fig. 4 (b) and (C), during a period from t =92.93s to t =96.25s, the system side oscillation center is located in the C-side system, and in this oscillation scenario, due to the step-out center occurring in the C-side system, the voltage at the O point is seriously decreased, and both line protection and demodulation devices on both sides may be affected, so that a problem may occur when only the system oscillation center is adopted for identification, and determination needs to be performed by using each system side oscillation center.
Taking side A as an example, the analysis result of the step-out center positioning criterion is analyzed. In the formula (20), epsilon =0.001 is taken, and preliminary screening is performed with the criterion of satisfying formula (a) in the main criterion 1 or the main criterion 2, and the determination result and the oscillation center position information are shown in table 1. Comparing the voltage curve in fig. 5 (a), it can be known that the positioning method can accurately position the step-out center. And the out-of-sync center may move in different locations on the same side system, or in different side systems.
TABLE 1
| t | δ 12 | δ 13 | Main criterion 1 | Main criterion 2 | Additional criteria | Function of position |
| 43.76s | 131.277° | 218.795° | √ | × | √ | 0.7379 |
| 180s | 180° | 180° | × | √ | √ | 0.6364 |
| 316.2s | 228.597° | 141° | √ | × | √ | 0.7379 |
In the case of impedance parameters and voltage amplitudes that are consistent with the basic model, consideration is given toAndrespectively at Δ ω 12 =2 °/s and Δ ω 13 Relative angular velocity of =5 °/s aroundAnd (4) rotating. In the oscillation process, the oscillation center position and the oscillation center voltage amplitude of each side are shown in fig. 5, in which curve 1 represents the value of the oscillation center position function of each side and curve 2 represents the oscillation center voltage amplitude. As can be seen from fig. 5, during the oscillation process, the shift range of the oscillation center is the same as that in fig. 4, but in this oscillation mode, the oscillation center first shifts back and forth on L1 and L2, and then moves to L3, and the oscillation center may appear on three lines.
Considering the voltage amplitude ratio and the same in the oscillation mode basic model, the A-side system parameter changes to Z AΣ Fig. 6 shows the oscillation center position and the oscillation center voltage amplitude of each side when the other side parameters are unchanged, where curve 1 represents the value of the function of the oscillation center position of each side, and curve 2 represents the oscillation center voltage amplitude. At this time, the A-side oscillation center shiftsThe shift range boundary value is 0.67045, the oscillation center shift range is narrowed, the B-side and C-side boundary values are 0.75641 and 0.84286, respectively, and the shift range is enlarged.
Considering that the voltage amplitude ratio and the oscillation mode are the same as those in the basic model, the B-side system parameter changes to Z AΣ Fig. 7 shows the oscillation center position and the oscillation center voltage amplitude of each side when =30 ≈ 86.5 Ω and other side parameters are unchanged, where a curve 1 represents the value of the oscillation center position function of each side and a curve 2 represents the oscillation center voltage amplitude. At this time, the oscillation center shifts only in the a-side and C-side ranges.
Considering that the system impedance parameter and the oscillation mode are the same as the basic model, k in the simulation 12 ，k 13 In the case of different values, the function of the oscillation center position on each side is shown in fig. 8. As can be seen from fig. 8, the change in the potential amplitude ratio directly affects the shift range of the oscillation center. When k is 12 K is 1.05 and 13 if =1.1, the range of the oscillation center transition on the a side becomes small, and the oscillation center transition law coincides with the case where the voltage amplitude ratio is equal. When k is 12 =0.95 and k 13 When =0.95, the oscillation center transition range increases. Specifically, when the power angle differences are all close to 0, the oscillation center passes through the inside of the a-side system to reach the back side of the a-side system, but at this time, no step-out center exists in the a-side system, and therefore, no consideration is needed. Table 2 and Table 3 show k 12 ＝0.95,k 13 =0.95 and k 12 ＝1.05,k 13 The results of positioning the out-of-step center under the two conditions of =1.1 show that the method can accurately position the out-of-step center under various scenes.
TABLE 2
TABLE 3
| t | δ 12 | δ 13 | Main criterion 1 | Main criterion 2 | Additional criteria | Function of position |
| 43.47s | 130.407° | 217.345° | √ | × | √ | 0.7277 |
| 180s | 180° | 180° | × | √ | √ | 0.6208 |
| 316.5s | 229.497° | 142.495° | √ | × | √ | 0.7125 |
The above embodiments are only preferred embodiments of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are also within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (6)
1. A multi-frequency oscillation out-of-step oscillation center positioning and migration tracking system based on a position function is characterized by comprising a system information acquisition module, an oscillation center position migration tracking module, an out-of-step oscillation center positioning module and an out-of-step oscillation center position output module which are sequentially connected; the system information acquisition module is used for acquiring system structural parameters, power angles, rotating speeds and voltage amplitudes of generators on all sides of the system and sending acquired data to the step-out center positioning module; the oscillation center position migration tracking module calculates the oscillation center position of each side of the system by using the information acquired by the information acquisition module, so that the tracking and analysis of the drift path of the oscillation center of the multi-frequency oscillation system are realized; the step-out center positioning module is used for positioning the position of a step-out center in the system according to the provided step-out center positioning criterion; and the step-out oscillation center position output module is used for outputting a step-out center position and an oscillation center drift path.
2. A multi-frequency oscillation out-of-step oscillation center positioning and migration tracking method based on a position function is characterized by comprising the following steps:
step 1: three power supplies are connected to one point through three lines to construct a three-machine equivalent system model;
step 2: obtaining a voltage vector expression of any point under the simultaneous action of the three-side power supply according to the superposition theorem;
and step 3: setting an oscillation center position function according to the line impedance ratio; rewriting a voltage vector expression of any point into a mode value and phase form, expanding the mode value and phase form into a quadratic function, calculating a partial derivative, and then obtaining an expression of the oscillation center position of any side according to a trigonometric function relation and a mean inequality;
and 4, step 4: analyzing the influence of three factors of a system relative power angle, impedance structure parameters and system power supply voltage amplitude on an oscillation center, obtaining the condition of the occurrence of the step-out center on each side, and determining the position of the step-out center after obtaining a criterion according to the trigonometric function relation of voltage vectors.
3. The method of claim 2, wherein the voltage vector expression is expressed with side a as follows:
in the formula (I), the compound is shown in the specification,is the voltage vector at any point p in the a-side line,for the equivalent potential of the A-side system, p is the distance from any point rho to the bus A, and delta 12 And delta 13 Respectively equal potential of B side systemEquivalent potential of A side systemC-side systemEquivalent potentialEquivalent potential of A side systemThe phase angle difference between the two phases is small,is the voltage amplitude ratio of the equivalent potential of the B-side system to the equivalent potential of the A-side system,the voltage amplitude ratio of the equivalent potential of the C-side system to the equivalent potential of the A-side system, the intermediate variableIntermediate variablesZ AΣ ＝Z A +Z AO ，Z BΣ ＝Z B +Z BO ，Z CΣ ＝Z C +Z CO ，Z AΣ 、Z BΣ 、Z CΣ Respectively representing the combined impedance of the A-side, B-side and C-side systems, Z A 、Z B 、Z C Respectively represent the equivalent power source impedance of the system at the A side, the B side and the C side, Z AO 、Z BO 、Z CO Equal impedance of A, B, C three-side line.
4. The method according to claim 3, wherein the expression of the oscillation center position on any side is expressed with side a as follows:
i may take A, B, C, f i (delta) represents A, B, C side oscillations, respectivelyThe function of the oscillation center position, taking i as A for example,S 2 and S 1 The quadratic and the first order coefficient respectively of the voltage magnitude factor of the system for the position p,
5. the method of claim 4, wherein the condition for the occurrence of the out-of-step center on each side is:
wherein the coefficient k may be [0, + ∞ [ ]]Any value in the range between (a) and (b),three lines are connected with the voltage phasor of the point O,intermediate variables
6. The method of claim 5, wherein the criteria include main criterion 1, main criterion 2, and auxiliary criterion, and wherein main criterion 1 is:
wherein epsilon is a protection action judgment threshold; the main criterion 2 is:
the auxiliary criterion is:
wherein k is the ratio of the voltage at the point O to the electromotive force amplitude of the generator at each side; when the main criterion 1 and the main criterion 2 meet one of the two criteria, the next calculation can be carried out; if the out-of-step center falls within the A-side system, it is also necessary to consider k ∈ [0, + ∞]I.e. byIf the main criterion and the auxiliary criterion are met simultaneously, the step-out center is in the A-side system, and the position of the step-out center is as follows:
in the formula, p 0 Representing the ratio of the impedance distance between the step-out center and the A-side system to the comprehensive impedance of the A-side system, and finally obtaining the position function of the step-out center:
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN108400594A (en) * | 2018-03-27 | 2018-08-14 | 云南电网有限责任公司 | A kind of method and system of determining Power System Oscillation Center Transport |
| CN108736492A (en) * | 2018-05-21 | 2018-11-02 | 云南电网有限责任公司 | A kind of composite information out-of-step solution method and system for oscillation center migration |
| CN110690716A (en) * | 2019-08-16 | 2020-01-14 | 中国电力科学研究院有限公司 | Method and system for positioning active splitting section of power grid based on voltage trajectory information |
| CN110736939A (en) * | 2019-11-07 | 2020-01-31 | 林心 | dynamic identification system for oscillation center of power system |
| CN110763940A (en) * | 2019-11-07 | 2020-02-07 | 林心 | Method for estimating oscillation center of power system by using phasor diagram method |
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| CN107134776A (en) * | 2017-06-27 | 2017-09-05 | 华北电力大学 | The centralized positioning of multi frequency system asynchronous oscillation and displacement path tracing system and method |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108400594A (en) * | 2018-03-27 | 2018-08-14 | 云南电网有限责任公司 | A kind of method and system of determining Power System Oscillation Center Transport |
| CN108736492A (en) * | 2018-05-21 | 2018-11-02 | 云南电网有限责任公司 | A kind of composite information out-of-step solution method and system for oscillation center migration |
| CN110690716A (en) * | 2019-08-16 | 2020-01-14 | 中国电力科学研究院有限公司 | Method and system for positioning active splitting section of power grid based on voltage trajectory information |
| CN110736939A (en) * | 2019-11-07 | 2020-01-31 | 林心 | dynamic identification system for oscillation center of power system |
| CN110763940A (en) * | 2019-11-07 | 2020-02-07 | 林心 | Method for estimating oscillation center of power system by using phasor diagram method |
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