CN111654038B - Method and system for identifying transient instability of power system based on track characteristics - Google Patents
Method and system for identifying transient instability of power system based on track characteristics Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention discloses a method and a system for identifying transient instability of a power system based on track characteristics, and belongs to the technical field of transient stability analysis of the power system. The method comprises the following steps: acquiring real-time operation parameters of a target power system synchronously measured by a WAMS (wide area measurement system), and performing digital filtering processing on the synchronously measured real-time operation parameters; the target power system is equivalent to a single machine infinite system SMIB through stability-preserving transformation, and an extended phase trajectory of the target power system is determined according to real-time operation parameters of the equivalent SMIB; acquiring an intercept value of an extended phase trajectory tangent on an angular acceleration axis, and extracting transient stability characteristics of a target power system; and determining whether the target power system is transient unstable or not according to the transient stability criterion of the extended phase trajectory and by combining the transient stability characteristics extracted in real time. The method can correctly identify the transient stability condition of the system, has better predictability, and provides time margin for implementing the stability control measure.
Description
Technical Field
The present invention relates to the field of power system transient stability analysis systems, and more particularly, to a method and system for identifying transient instability of a power system based on trajectory features.
Background
Large-area power failure accidents in the world are mostly caused by transient instability of the power system, and a rapid and reliable transient stability analysis method is an important link of online safety analysis of the power system. With the continuous enlargement of the scale of the alternating-current and direct-current hybrid power grid and the continuous improvement of the intermittent new energy ratio, the operation characteristics of the power grid have changed remarkably, and the operation mode of the power grid is more complicated and changeable. The traditional transient stability distinguishing mode of 'off-line decision and on-line matching' cannot meet the requirements of modern power grids, and a real-time on-line transient stability analysis method gradually becomes the key point of relevant research.
The real-time and global measurement information provided by a Wide Area Measurement System (WAMS) provides a new approach for transient stability online analysis and control. Related researches on WAMS-based wide area transient stability criteria have been carried out at home and abroad, and the researches mainly comprise fixed phase angle difference, a transient energy function method, expansion equal area criteria, response track characteristics and the like. The wide-area out-of-step separation system of Tokyo electric power company of Japan utilizes the global information collected by WAMS to construct the transient out-of-step criterion based on the fixed phasor angular difference, but the phasor angular difference serving as a threshold value in the criterion is difficult to define uniformly and accurately, and the reliability of the criterion is poor depending on the historical data of system operation and the experience judgment of scheduling personnel. An extended equivalent-area criterion (EEAC) proposed and developed by scholars in China in the 80 th of the 20 th century is a rapid transient stability analysis method, and a power angle running track of an equivalent single-machine infinite system is obtained through complementary cluster inertia center-relative motion (CCCOI-RM) transformation, so that the transient stability condition of an electric power system can be rapidly judged. For an ideal Hamiltonian system, the EEAC can reliably judge the system instability, but for a multi-machine system with strong time variation, the EEAC still needs to be further developed on the problems of transient stability analysis commonality such as power system instability mode identification, transient stability evaluation accuracy and computational speed game and the like.
When the power system is subjected to large disturbance and out-of-step oscillation occurs, the response track of the system in a phase plane has the characteristic of concave-convex change. In combination with the track change characteristic of the instability system, relevant researches have been carried out to provide a transient stability criterion of the power system based on the track concavity and convexity. The criterion can predictively judge the transient stability of the power system, but the phase trajectory is difficult to intuitively reflect the transient stability trend change of the system. Compared with system state variables such as power angles and angular velocities, the angular acceleration can more directly represent the transient stability change trend of the system. Therefore, it is necessary to construct an extended phase trajectory of the system on an extended phase plane formed by angular velocity and angular acceleration based on actual measurement response information of the power system acquired by the wide-area measurement system, and to study a transient stability determination method based on the extended phase trajectory characteristics.
Disclosure of Invention
In order to solve the above problems, the present invention provides a method for identifying transient instability of an electric power system based on trajectory features, comprising:
acquiring real-time operation parameters of a target power system synchronously measured by a Wide Area Measurement System (WAMS), and performing digital filtering processing on the synchronously measured real-time operation parameters;
the target power system is equivalent to a single machine infinite system SMIB through stability-preserving transformation, and an extended phase trajectory of the target power system is determined according to real-time operation parameters of the equivalent SMIB;
acquiring an intercept value of an extended phase trajectory tangent on an angular acceleration axis, and extracting transient characteristics of a target power system in real time;
and determining whether the target power system is transient unstable or not according to the transient stability criterion of the extended phase trajectory and by combining the transient stability characteristics extracted in real time.
Optionally, the real-time operation parameters include: synchronous power angle deviation of each unit, unbalanced power value of each unit and bus voltage phase difference.
Optionally, the digital filtering process is a smoothing filtering process and a low-pass filtering process.
Optionally, the stability preserving transform is a complementary cluster interpopulation inertia center-relative motion CCCOI-RM transform.
Optionally, determining an extended phase trajectory of the target power system includes:
determining the generalized angular velocity and the generalized angular acceleration of the equivalent SMIB according to the synchronous power angle value of the equivalent SMIB;
and generating an extended phase locus of the target power system by taking the angular velocity as an abscissa and the angular acceleration as an ordinate.
Optionally, the transient stability criterion specifically includes:
when the generalized angular velocity is larger than 0, the generalized angular acceleration is smaller than 0 and the intercept value of the tangent line of the transient stability extended phase trajectory on the angular acceleration axis is smaller than 0 after the target power system fails, the transient stability of the target power system is achieved;
when the generalized angular velocity is larger than 0 and the generalized angular acceleration is smaller than 0 after the target power system fails, the intercept value of the transient stability extended phase trajectory tangent line on the angular acceleration axis is larger than or equal to 0 and meets the auxiliary criterion, or when the generalized angular velocity of the first pendulum is larger than 0 and the generalized angular acceleration is larger than 0 and the intercept value of the transient stability extended phase trajectory tangent line on the angular acceleration axis is smaller than 0 after the target power system fails, the target power system is unstable in transient state.
Optionally, the auxiliary criterion is:
the formula of the auxiliary criterion constructed by the equivalent SMIB set unbalance power delta P is as follows:
(ΔP″(t)·ΔP(t)-ΔP′(t)·ΔP′(t))＜0
wherein, Δ P is the unbalanced power value of WAMS measured unit at the time t, Δ P '(t) is the first derivative of the unbalanced power at the time SMIB after CCCOI-RM conversion, and Δ P' (t) is the second derivative of the unbalanced power at the time SMIB after CCCOI-RM conversion.
The invention also provides a system for identifying transient instability of the power system based on the track characteristics, which comprises the following steps:
the preprocessing module is used for acquiring real-time operation parameters of a target power system synchronously measured by the WAMS and carrying out digital filtering processing on the synchronously measured real-time operation parameters;
the track extraction module is used for enabling the target electric power system to be equivalent to a single-machine infinite system SMIB through stability-preserving transformation, and determining an extended phase track of the target electric power system according to real-time operation parameters of the equivalent SMIB;
the characteristic extraction module is used for acquiring an intercept value of an extended phase trajectory tangent on an angular acceleration axis and extracting transient characteristics of a target power system in real time;
and the judging module is used for determining whether transient characteristics are instable or not according to the transient stability criterion of the extended phase trajectory, and determining the transient instability of the target power system when the transient characteristics are instable.
Optionally, the real-time operation parameters include: the method comprises the steps of synchronous power angle deviation of each unit, unbalanced power value of each unit and bus voltage phase difference.
Optionally, the digital filtering process is a smoothing filtering process and a low-pass filtering process.
Optionally, the stability preserving transform is a complementary cluster interpopulation inertia center-relative motion CCCOI-RM transform.
Optionally, determining an extended phase trajectory of the target power system includes:
determining the generalized angular velocity and the generalized angular acceleration of the equivalent SMIB according to the synchronous power angle value of the equivalent SMIB;
and generating an extended phase locus of the target power system by taking the angular velocity as an abscissa and the angular acceleration as an ordinate.
Optionally, the transient stability criterion specifically includes:
when the generalized angular velocity is larger than 0, the generalized angular acceleration is smaller than 0 and the intercept value of the tangent line of the extended phase trajectory on the angular acceleration axis is smaller than 0 after the target power system fails, the transient state of the target power system is stable;
when the generalized angular velocity is larger than 0 and the generalized angular acceleration is smaller than 0 after the target power system fails, the intercept value of the extended phase trajectory tangent line on the angular acceleration axis is larger than or equal to 0 and meets the auxiliary criterion, or when the generalized angular velocity of the first pendulum is larger than 0 and the generalized angular acceleration is larger than 0 and the intercept value of the extended phase trajectory tangent line on the angular acceleration axis is smaller than 0 after the target power system fails, the target power system is unstable in transient state.
Optionally, the auxiliary criterion is:
the formula of the auxiliary criterion constructed by the equivalent SMIB set unbalanced power delta P is as follows:
(delta P '(t) delta P (t) -delta P' (t)) < 0, wherein delta P is the unbalance power value at the moment t of the WAMS measured unit, delta P '(t) is the first derivative of the unbalance power at the moment t of SMIB after CCCOI-RM conversion, and delta P' (t) is the second derivative of the unbalance power at the moment t of SMIB after CCCOI-RM conversion.
The invention utilizes the expanded phase track constructed by the actually measured wide area response information of the system to correctly identify the transient stability condition of the system, and for the system losing the transient stability after disturbance, the criterion can judge the transient instability of the system before the track crosses the DSP, and the judgment time is obviously earlier than the moment when the system slips, so that the invention has better predictability and provides time margin for implementing the stability control measure.
Drawings
FIG. 1 is a flow chart of a method for identifying transient instability of an electrical power system based on trajectory characteristics according to the present invention;
FIG. 2 is an expanded item trajectory of a stabilization system according to an embodiment of the method for identifying transient instability of an electric power system based on trajectory features of the present invention;
FIG. 3 is an expansion item trajectory of instability of an embodiment of a method for identifying transient instability of an electric power system based on trajectory features of the present invention under large disturbance of the system;
FIG. 4 is an expanded item trajectory of a power system transient instability system under small disturbance according to an embodiment of a method for identifying transient instability of a power system based on trajectory features of the present invention;
FIG. 5 is a flow chart of the method for identifying transient instability of an electric power system based on trajectory features to determine system instability according to the present invention;
fig. 6 is a system structure diagram for identifying transient instability of the power system based on the trajectory features according to the present invention.
Detailed Description
The exemplary embodiments of the present invention will now be described with reference to the accompanying drawings, however, the present invention may be embodied in many different forms and is not limited to the embodiments described herein, which are provided for complete and complete disclosure of the present invention and to fully convey the scope of the present invention to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the accompanying drawings is not intended to be limiting of the invention. In the drawings, the same unit/element is denoted by the same reference numeral.
Unless otherwise defined, terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Further, it will be understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense.
The invention provides a method for identifying transient instability of a power system based on track characteristics, which comprises the following steps of:
acquiring real-time operation parameters of a target power system synchronously measured by a Wide Area Measurement System (WAMS), and performing digital filtering processing on the synchronously measured real-time operation parameters;
the target power system is equivalent to a single-machine infinite system SMIB through stability-preserving transformation, and the extended phase trajectory of the target power system is determined according to the real-time operation parameters of the equivalent SMIB;
acquiring an intercept value of an extended phase trajectory tangent on an angular acceleration axis, and extracting transient characteristics of a target power system in real time;
and determining whether the target power system is transient unstable or not according to the transient stability criterion of the extended phase trajectory and by combining the transient stability characteristics extracted in real time.
Wherein, the real-time operation parameters include: the method comprises the steps of synchronous power angle deviation of each unit, unbalanced power value of each unit and bus voltage phase difference.
The digital filtering process is a smoothing filtering process and a low-pass filtering process.
The stability preserving transform is a complementary group interpopular inertia center-relative motion CCCOI-RM transform.
Determining an extended phase trajectory for a target power system, comprising:
determining the generalized angular velocity and the generalized angular acceleration of the equivalent SMIB according to the synchronous power angle value of the equivalent SMIB;
and generating an extended phase locus of the target power system by taking the angular velocity as an abscissa and the angular acceleration as an ordinate.
Optionally, the transient stability criterion specifically includes:
when the generalized angular velocity is larger than 0, the generalized angular acceleration is smaller than 0 and the intercept value of the tangent line of the extended phase trajectory on the angular acceleration axis is smaller than 0 after the target power system fails, the transient state of the target power system is stable;
when the generalized angular velocity is larger than 0 and the generalized angular acceleration is smaller than 0 after the target power system fails, the intercept value of the extended phase trajectory tangent line on the angular acceleration axis is larger than or equal to 0 and meets the auxiliary criterion, or when the generalized angular velocity of the first pendulum is larger than 0 and the generalized angular acceleration is larger than 0 and the intercept value of the extended phase trajectory tangent line on the angular acceleration axis is smaller than 0 after the target power system fails, the target power system is unstable in transient state.
The auxiliary criterion is as follows:
the formula of the auxiliary criterion constructed by the equivalent SMIB set unbalance power delta P is as follows:
(ΔP″(t)·ΔP(t)-ΔP′(t)·ΔP′(t))＜0
and delta P is an unbalanced power value at t moment of the WAMS actual measurement unit, delta P '(t) is a first derivative of unbalanced power at SMIB t moment after CCCOI-RM conversion, and delta P' (t) is a second derivative of unbalanced power at SMIB t moment after CCCOI-RM conversion.
The present invention will be further illustrated with reference to the following examples;
the instability process of the power system after the fault does not depend on the transient energy of the whole system, but is dominated by the transient energy of a single machine or a part of machine groups which tend to be separated from the system, the equivalence of the multi-machine system in a two-group instability mode can be transformed into a Single Machine Infinite Bus (SMIB) system through CCCOI-RM transformation, the stability of the system is not changed, and the stability or instability trend of the system can be represented by the slope of a track tangent line in a 2 nd quadrant and the intercept of an angular acceleration gamma axis:
stabilizing the extended phase trajectory of the system after a fault;
for a stable system, after the fault is removed, the trajectory enters the second quadrant and passes through the gamma axis to enter the third quadrant, as shown in fig. 2, the main process of the tangent slope change in the 2 nd quadrant of the extended phase trajectory is as follows: after the minimum point of the track is crossed, the tangent slope value is gradually reduced, and the intercept value on the gamma axis is gradually increased; when the track runs to the point N2, the slope of the tangent reaches the minimum value, and the intercept value of the point M2 intersected with the gamma axis reaches the maximum value; after the track crosses the N2 point, the tangent slope value is gradually increased, and the intercept value on the gamma axis is gradually reduced. Therefore, the intercept value of the tangent to the stationary extended phase trajectory in quadrant 2 on the γ axis remains negative at all times.
An extended phase trajectory of the post-fault instability system;
for a system that loses stability, there are two cases of extending the phase trajectory after a fault: when the system is in transient desynchronization under a serious fault, the system starts an acceleration process without deceleration after the fault, and rapidly loses synchronization, as shown in fig. 3, the track does not enter a 2 nd quadrant on a phase track, the slope of a track tangent line is positive in the 1 st quadrant, and the intercept value on a gamma axis is negative.
When the system is subjected to transient instability after relatively small disturbance, the fault-removed track enters the second quadrant and passes through the omega axis to return to the third quadrant, as shown in fig. 4, compared with a stable system, after the extended phase track of the instability system passes over the lowest point of the track, the tangent slope value always keeps a decreasing trend and finally tends to- ∞; the intercept value on the gamma axis keeps increasing, changes from negative to positive and finally tends to + ∞, and the tangent line of the track changes from M1-N1 to M2-N2 and then to M3-N3; the corresponding intercept values range from a negative value at point M1, to 0 at point M2, and to a positive value at point M3.
The WAMS can synchronously measure the real-time operation parameters of a wide area power grid with high precision, provides conditions for utilizing the stability condition of an extended phase trajectory characteristic analysis system, and synchronously measures the power angle value delta of each unit in real time i (t) carrying out CCCIO-RM transformation to obtain the value of the synchronization power angle of the equivalent SMIB system, wherein the formula is as follows:
wherein, delta i (T) represents the real-time power angle of the ith unit at the time T, T ji The moment of inertia of the unit i is shown, S is the leading cluster set, and A is the lagging cluster set.
The differential expression of the generalized angular velocity ω (t) and the angular acceleration γ (t) of the equivalent SMIB system at time t is as follows:
wherein, Δ t is the system real-time sampling interval duration, therefore, the tangent expression on the extended phase trajectory is:
the intercept value of the tangent on the gamma axis can be derived as:
the influence of two factors needs to be considered in the practical application of the criterion:
interference and errors exist in the acquisition, transmission and processing processes of phasor data by the WAMS;
automatic adjustment device action, grid topology changes, etc. may cause abrupt changes in the amount of angular velocity, the amount of angular acceleration.
Aiming at the influence factors, on one hand, an extended phase track is established by using the relative power angle difference between the inertia centers of the polymerization cluster after CCCOI-RM transformation, and the track is insensitive to the change of a topological structure;
on the other hand, in the application of the criterion, a proper digital filter such as smooth filtering, low-pass filtering and the like can be selected according to the actual situation to process the acquired phasor data, and in addition, in order to further improve the reliability of the criterion, the instability of the system can be judged when a plurality of continuous sampling points on the track simultaneously meet the instability criterion in the actual application.
In conjunction with the above analysis of the extended phase trajectory stability trend, a transient stability criterion based on the extended phase trajectory may be formed:
and (3) transient stability of the system: when the extended phase trajectory satisfies omega > 0 and gamma < 0, the gamma-axis intercept value D γ < 0 is always true.
Transient instability of the system and expansion phase trajectory have two conditions:
when the first pendulum omega is more than 0 and gamma is less than 0 after the fault, the intercept value D of the gamma axis γ Not less than 0, and meets the auxiliary criterion;
when the system suffers serious failure, omega is more than 0, and gamma is more than 0, the gamma-axis intercept value D γ ＜0。
Considering the influence of nonlinear factors in the system on the criterion, in order to enhance the reliability of the criterion, constructing an auxiliary criterion by using the unbalanced power value delta P and the derivative thereof of the WAMS actual measurement unit at the time t:
(ΔP″(t)·ΔP(t)-ΔP′(t)·ΔP′(t))＜0(6)
wherein, Δ P' (t) represents the first derivative of the unbalanced power at the moment t of the SMIB system after CCCOI-RM transformation, and Δ P "(t) represents the second derivative of the unbalanced power at the moment t of the SMIB system after CCCOI-RM transformation.
And when the WAMS acquires the extended phase track constructed by the wide area measurement information in n continuous sampling periods and simultaneously satisfies the expression (6), judging the transient instability of the system by the criterion.
In expression (6):
wherein, Δ P i (T) represents the unbalanced power of the i-th unit at time T, T ji The moment of inertia of the unit i is shown, S is the leading cluster set, and A is the lagging cluster set.
The first and second derivative difference form of the unbalanced power Δ P is:
the process of determining system instability according to the stabilization criterion, as shown in fig. 5, includes:
step 1: and setting basic parameters of the criterion. The parameters include: judging the continuous sampling period number n of the transient instability of the system, the band-pass frequency of a digital filter, an attenuation coefficient and the like; the initialization continuous instability count =0.
And 2, step: input WAMS collected actually-measured unit power angle deviation value delta i (t) unbalanced power value delta P of unit i And (t) processing the actually measured data through a digital filter to eliminate errors and interference in the data.
And step 3: and respectively carrying out CCCII-RM transformation on the filtered measured data according to the expression (1) and the expression (7), and calculating the angular speed omega (t) and the angular acceleration gamma (t) of the equivalent SMIB system after transformation according to the expression (2) and the expression (3).
And 4, step 4: calculating the gamma-axis intercept value D of the extended phase trajectory at the current moment according to the expression (5) γ 。
And 5: if omega (t) > 0 and gamma (t) > 0, entering the step 6; otherwise, go to step 8.
Step 6: if the 1 st pendulum after the current system fault, entering the step 7; otherwise, step 12 is entered.
And 7: if the intercept value D of the gamma axis of the phase trajectory is expanded γ If the temperature is less than or equal to 0, entering step 13; otherwise, step 12 is entered.
And step 8: if omega (t) > 0 and gamma (t) < 0, entering step 9; otherwise, step 12 is entered.
And step 9: if D is γ If the value is more than or equal to 0, entering the step 10; otherwise, go to step 12.
Step 10: the first derivative Δ P' (t), the second derivative Δ P ″ (t) of the imbalance power Δ P (t) is calculated.
Step 11: if (Δ P ' (t) · Δ P (t) - Δ P ' (t) · Δ P ('t)) < 0, proceed to step 13; otherwise, step 12 is entered.
Step 12: and (4) the transient state of the system is stable, the continuous instability count is cleared to zero =0, the step 2 is returned, and the next sampling period is started for judgment.
Step 13: the continuous instability count = count +1, whether the count reaches a preset continuous sampling cycle number count for judging transient instability of the system, which is not less than n, is judged, and if yes, the step 15 is executed; otherwise, step 14 is entered.
Step 14: and (5) the system has a transient instability trend, returns to the step 2, and enters the next sampling period for judgment.
Step 15: and judging the transient instability of the system, and ending.
The present invention further provides a system 200 for identifying transient instability of an electrical power system based on trajectory features, as shown in fig. 6, including:
the preprocessing module 201 is used for acquiring real-time operation parameters of a target power system synchronously measured by the wide area measurement system WAMS and performing digital filtering processing on the synchronously measured real-time operation parameters;
the trajectory extraction module 202 is used for enabling the target electric power system to be equivalent to a single-machine infinite system SMIB through stability-preserving transformation, and determining an extended phase trajectory of the target electric power system according to real-time operation parameters of the equivalent SMIB;
the feature extraction module 203 is used for acquiring an intercept value of an extended phase trajectory tangent on an angular acceleration axis and extracting transient features of the target power system in real time;
the determining module 204 determines whether transient characteristics are unstable according to a transient stability criterion of the extended phase trajectory, and determines transient instability of the target power system when the transient characteristics are unstable.
Wherein, the real-time operation parameters include: the method comprises the steps of synchronous power angle deviation of each unit, unbalanced power value of each unit and bus voltage phase difference.
The digital filtering process is a smoothing filtering process and a low-pass filtering process.
The stability preserving transform is a complementary group interpopular inertia center-relative motion CCCOI-RM transform.
Determining an extended phase trajectory for a target power system, comprising:
determining the generalized angular velocity and the generalized angular acceleration of the equivalent SMIB according to the synchronous power angle value of the equivalent SMIB;
and generating an extended phase locus of the target power system by taking the angular velocity as an abscissa and the angular acceleration as an ordinate.
The transient stability criterion is specifically as follows:
when the generalized angular velocity is larger than 0, the generalized angular acceleration is smaller than 0 and the intercept value of the tangent line of the extended phase trajectory on the angular acceleration axis is smaller than 0 after the target power system fails, the transient state of the target power system is stable;
when the generalized angular velocity is larger than 0 and the generalized angular acceleration is smaller than 0 after the target power system fails, the intercept value of the extended phase trajectory tangent on the angular acceleration axis is larger than or equal to 0 and meets the auxiliary criterion, or when the generalized angular velocity of the first pendulum is larger than 0 and the generalized angular acceleration is larger than 0 and the intercept value of the transient stability extended phase trajectory tangent on the angular acceleration axis is smaller than 0 after the target power system fails, the target power system is unstable in transient state.
The auxiliary criterion is:
the formula of the auxiliary criterion constructed by the equivalent SMIB set unbalanced power delta P is as follows:
(Δ P '(t). Δ P (t) - Δ P' (t). Δ P '(t)) < 0, where Δ P is the value of the imbalance power at time t of the WAMS measured train, Δ P' (t) is the first derivative of the imbalance power at time SMIB t after CCCOI-RM transformation, and Δ P "(t) is the second derivative of the imbalance power at time SMIB t after CCCOI-RM transformation.
The invention utilizes the extended phase track constructed by the actually measured wide area response information of the system to correctly identify the transient stability condition of the system, and for the system losing the transient stability after disturbance, the criterion can judge the transient instability of the system before the track passes over the DSP, and the judgment time is obviously earlier than the moment when the system slips, so that the invention has better predictability and provides time margin for the implementation of the stability control measure.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and so forth) having computer-usable program code embodied therein. The scheme in the embodiment of the application can be implemented by adopting various computer languages, such as object-oriented programming language Java and transliterated scripting language JavaScript.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While the preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the present application.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Claims (8)
1. A method of identifying power system transient instability based on trajectory characteristics, the method comprising:
acquiring real-time operation parameters of a target power system synchronously measured by a Wide Area Measurement System (WAMS), and performing digital filtering processing on the synchronously measured real-time operation parameters;
the target power system is equivalent to a single-machine infinite system SMIB through stability-preserving transformation, and the extended phase trajectory of the target power system is determined according to the real-time operation parameters of the equivalent SMIB;
the determining of the extended phase trajectory of the target power system includes:
determining the generalized angular velocity and the generalized angular acceleration of the equivalent SMIB according to the synchronous power angle value of the equivalent SMIB;
generating an extended phase trajectory of the target power system by taking the angular velocity as an abscissa and the angular acceleration as an ordinate;
acquiring an intercept value of an extended phase trajectory tangent on an angular acceleration axis, and extracting transient stability characteristics of a target power system in real time;
determining whether transient instability occurs in a target power system or not according to transient stability criteria of the extended phase trajectory and by combining transient stability characteristics extracted in real time;
the transient stability criterion is specifically as follows:
when the target power system has a fault, the generalized angular velocity is greater than 0, the generalized angular acceleration is less than 0, and the intercept value of the tangent of the extended phase trajectory on the angular acceleration axis is less than 0, the target power system is stable in transient state;
when the generalized angular velocity of the target power system is greater than 0 after the fault, the generalized angular acceleration is less than 0, the intercept value of the extended phase trajectory tangent on the angular acceleration axis is greater than or equal to 0 and meets the auxiliary criterion, or the generalized angular velocity of the first pendulum is greater than 0 after the fault of the target power system, the generalized angular acceleration is greater than 0, and the intercept value of the extended phase trajectory tangent on the angular acceleration axis is less than 0, the target power system is instable in transient state;
the auxiliary criterion is:
the formula of the auxiliary criterion constructed by the equivalent SMIB set unbalanced power delta P is as follows:
(ΔP″(t)·ΔP(t)-ΔP′(t)·ΔP′(t))＜0
wherein, Δ P is the unbalanced power value at t moment of WAMS actual measurement unit, Δ P '(t) is the first derivative of the unbalanced power at SMIB t moment after CCCOI-RM conversion, and Δ P' (t) is the second derivative of the unbalanced power at SMIB t moment after CCCOI-RM conversion.
2. The method of claim 1, the real-time operating parameters comprising: synchronous power angle deviation of each unit, unbalanced power value of each unit and bus voltage phase difference.
3. The method of claim 1, the digital filtering process being a smoothing filtering process and a low-pass filtering process.
4. The method of claim 1, wherein the stationary transform is a complementary group interpopular inertia center-relative motion CCCOI-RM transform.
5. A system for identifying transient instability of a power system based on trajectory characteristics, the system comprising:
the preprocessing module is used for acquiring real-time operation parameters of a target power system synchronously measured by the WAMS of the wide area measurement system and carrying out digital filtering processing on the synchronously measured real-time operation parameters;
the track extraction module is used for enabling the target electric power system to be equivalent to a single-machine infinite system SMIB through stability-preserving transformation, and determining an extended phase track of the target electric power system according to real-time operation parameters of the equivalent SMIB;
the determining of the extended phase trajectory of the target power system includes:
determining the generalized angular velocity and the generalized angular acceleration of the equivalent SMIB according to the synchronous power angle value of the equivalent SMIB;
generating an extended phase trajectory of the target power system by taking the angular velocity as an abscissa and the angular acceleration as an ordinate;
the characteristic extraction module is used for acquiring an intercept value of an extended phase trajectory tangent on an angular acceleration axis and extracting transient stability characteristics of a target power system in real time;
the judging module is used for determining whether the target power system has transient instability or not according to transient stability criteria of the extended phase trajectory and by combining transient stability characteristics extracted in real time;
the transient stability criterion is specifically as follows:
when the target power system has a fault, the generalized angular velocity is greater than 0, the generalized angular acceleration is less than 0, and the intercept value of the tangent of the extended phase trajectory on the angular acceleration axis is less than 0, the target power system is stable in transient state;
when the generalized angular velocity of the target power system is greater than 0 after the fault, the generalized angular acceleration is less than 0, the intercept value of the extended phase track tangent line on the angular acceleration axis is greater than or equal to 0 and meets the auxiliary criterion, or the generalized angular velocity of the first pendulum is greater than 0 after the fault of the target power system, the generalized angular acceleration is greater than 0, and the intercept value of the extended phase track tangent line on the angular acceleration axis is less than 0, the target power system is unstable in transient state;
the auxiliary criterion is as follows:
the formula of the auxiliary criterion constructed by the equivalent SMIB set unbalanced power delta P is as follows:
(ΔP″(t)·ΔP(t)-ΔP′(t)·ΔP′(t))＜0
wherein, Δ P is the unbalanced power value at t moment of WAMS actual measurement unit, Δ P '(t) is the first derivative of the unbalanced power at SMIB t moment after CCCOI-RM conversion, and Δ P' (t) is the second derivative of the unbalanced power at SMIB t moment after CCCOI-RM conversion.
6. The system of claim 5, the real-time operating parameters comprising: the method comprises the steps of synchronous power angle deviation of each unit, unbalanced power value of each unit and bus voltage phase difference.
7. The system of claim 5, the digital filtering process being a smoothing filtering process and a low pass filtering process.
8. The system of claim 5, the stuck-at transform being a complementary group interpopular inertia center-relative motion CCCOI-RM transform.
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