CN107229003A - The discrimination method and device of weakness zone temporarily drop in a kind of line voltage - Google Patents
The discrimination method and device of weakness zone temporarily drop in a kind of line voltage Download PDFInfo
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- CN107229003A CN107229003A CN201710581389.7A CN201710581389A CN107229003A CN 107229003 A CN107229003 A CN 107229003A CN 201710581389 A CN201710581389 A CN 201710581389A CN 107229003 A CN107229003 A CN 107229003A
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
- G01R31/081—Locating faults in cables, transmission lines, or networks according to type of conductors
- G01R31/086—Locating faults in cables, transmission lines, or networks according to type of conductors in power transmission or distribution networks, i.e. with interconnected conductors
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/08—Locating faults in cables, transmission lines, or networks
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Abstract
本发明公开了一种电网电压暂降薄弱区域的辨识方法及装置，该方法包括：根据获取的每条故障线路的故障类型，选择对应的电压方程；根据电压方程求解每条故障线路的首端点和尾端点故障引起的敏感性负荷接入点处的跌落幅值，并计算每条故障线路对应的薄弱性指标向量；根据薄弱性指标向量的数值，利用黄金分割法和/或割线迭代法确定每条故障线路对应的薄弱区域；本发明通过选择对应的电压方程，可以计算每条故障线路的上任意一点故障引起的敏感性负荷接入点处的跌落幅值；通过利用黄金分割法和/或割线迭代法确定每条故障线路对应的薄弱区域，可以利用黄金分割法和割线迭代法的混合方法，计算临界点，从而确定电网电压暂降薄弱区域。
The invention discloses a method and device for identifying weak areas of voltage sags in power grids. The method includes: selecting a corresponding voltage equation according to the obtained fault type of each faulty line; and solving the first terminal point of each faulty line according to the voltage equation and the drop amplitude at the sensitive load access point caused by the tail end point fault, and calculate the vulnerability index vector corresponding to each fault line; according to the value of the vulnerability index vector, use the golden section method and/or the secant iteration method Determine the weak area corresponding to each fault line; the present invention can calculate the drop amplitude at the sensitive load access point caused by any point fault on each fault line by selecting the corresponding voltage equation; by using the golden section method and /or the secant iteration method to determine the weak area corresponding to each fault line, the hybrid method of the golden section method and the secant iteration method can be used to calculate the critical point, so as to determine the weak area of the grid voltage sag.
Description
Technical Field
The invention relates to the field of power quality evaluation of power systems, in particular to a method and a device for identifying a weak voltage sag area of a power grid.
Background
With the development of high and new technologies in modern society, sensitive devices in an electric power system are gradually increased, and the voltage sag of a power grid can cause the sensitive devices to trip or misoperation, so that the whole process of a terminal user is influenced, and huge production and economic losses are caused. The voltage sag is defined by Institute of Electrical and Electronics Engineers (IEEE), and refers to a short-time voltage variation phenomenon that the voltage root mean square is reduced to 0.1-0.9 times of rated voltage under the power frequency condition, and the duration is 0.5 cycle (calculated by 50Hz in the power frequency of China, 1 cycle is 20ms) to 1 min. The voltage sag contains two features: the magnitude of the voltage sag and the duration of the voltage sag. Because system failures are unpredictable, voltage sags are random in nature. Therefore, the method has very important practical significance for analyzing and evaluating the voltage sag problem in the power system.
Effective countermeasures and mitigation plans for the voltage sag problem need to be evaluated for the system voltage sag performance. Estimating the expected droop frequency (ESF) on the system line is very effective in understanding the system voltage sag performance. Generally, the ESF estimation can be performed using the concepts of weak Areas (AOVs) and system failure statistics. The AOV may represent a fault range that causes the voltage amplitude at the sensitive load point to drop below a given voltage threshold. The ESF is calculated by multiplying the system fault statistics by the total length of the line and the number of lines contained in the AOV. Therefore, accurately determining the AOV is important for evaluating the voltage sag performance of the system.
In the prior art, as for identification methods of weak areas, such as a critical distance method and a fault location method, many defects or too much time is often generated in the calculation of critical points and weak areas of a large-scale power system, and in some cases, divergence occurs in the calculation of the critical points, and accurate and rapid identification of weak areas in power grid voltage sag cannot be performed. Therefore, how to provide a method for identifying a weak area of grid voltage sag with less calculation and higher reference reliability so as to analyze the voltage sag problem in the power system is a problem that needs to be solved urgently nowadays.
Disclosure of Invention
The invention aims to provide a method and a device for identifying a weak area of power grid voltage sag, which are used for determining the weak area of power grid voltage sag by using a mixed method of a golden section method and a secant iteration method, and have less calculation and higher reference reliability.
In order to solve the technical problem, the invention provides a method for identifying a weak area of power grid voltage sag, which comprises the following steps:
selecting a corresponding voltage equation according to the acquired fault type of each fault line; the voltage equation is used for calculating the drop amplitude of the sensitive load access point caused by any fault on the corresponding fault line;
solving the drop amplitude at the sensitive load access point caused by the faults of the head end point and the tail end point of each fault line according to the voltage equation, and calculating the corresponding weakness index vector of each fault line; the numerical value of the weakness index vector is the relation between the corresponding fault line and the weak area;
and determining a weak area corresponding to each fault line by using a golden section method and/or a secant iteration method according to the numerical value of the weak index vector.
Optionally, before solving the drop amplitude at the sensitive load access point caused by the fault at the head end point and the tail end point of each fault line according to the voltage equation and calculating the corresponding weakness index vector of each fault line, the method further includes:
calculating the voltage before the fault of each fault line through load flow analysis;
and acquiring a sequence impedance matrix of each fault line by using the sequence admittance matrix.
Optionally, the selecting a corresponding voltage equation according to the obtained fault type of each fault line includes:
if the obtained fault type of the current fault line is an A-phase single-phase earth fault, the selected voltage equation is as follows:andwherein s is a sensitive load access point of the currently faulty line,andphase voltage amplitudes of the A phase, the B phase and the C phase at the s point of the current fault line respectively,the voltage is the voltage before the fault at the point s of the current fault line;for the operation of a complex number, the operation is,the sequence voltage before the fault at the fault position K point of the current fault line is obtained;andrespectively positive, negative and zero sequence mutual impedance between the point s and the point K of the current fault line;andrespectively positive, negative and zero sequence self-impedance at the K point of the current fault line;
if the fault type of the current fault line is a two-phase short-circuit fault of a B phase and a C phase, the selected voltage equation is as follows:and
if the fault type of the current fault line is a two-phase short circuit ground fault of a B phase and a C phase, the selected voltage equation is as follows: and
if the fault type of the current fault line is a three-phase short-circuit fault, selecting a voltage equation as follows:wherein,the phase voltage amplitude at the s point of the current fault line.
Optionally, the solving, according to the voltage equation, the drop amplitude at the sensitive load access point caused by the fault at the head end point and the tail end point of each fault line, and calculating the corresponding weakness index vector of each fault line include:
according to a voltage equation corresponding to the current fault line, solving the drop amplitude at the sensitive load access point caused by the faults of the head end point and the tail end point of the current fault line; if the voltage equation corresponding to the current fault line is the voltage equation of the three-phase short-circuit fault, the drop amplitude | F (F) at the sensitive load access point caused by the fault of the head end point of the current fault linei) And the dip amplitude | f (T) at the sensitive load access point caused by the tail-end fault of the currently faulty linei) I are respectivelyAndif the voltage equation corresponding to the current fault line is not the voltage equation of the three-phase short-circuit fault, then | F (F)i) Is |Andminimum value of, | f (T)i) Is |Andminimum of (1)The value i is the current faulty line, FiIs the head end point, T, of the currently faulted lineiThe tail end point of the current fault line;
respectively subtracting the difference of voltage thresholds from the drop amplitudes at the sensitive load access points caused by the faults of the head end point and the tail end point of the current fault line, and comparing the difference with 0 to determine that the weaknesses index vectors of the head end point and the tail end point of the current fault line are 0 or 1; wherein, the weakness index vector of the head end point of the current fault lineWeakness indicator vector of tail end point of current fault lineVthIs the voltage threshold;
adding the weakness index vectors of the head point and the tail point of the current fault line to determine the weakness index vector of the current fault line; wherein the weakness index vector of the current fault line
Optionally, the determining, according to the value of the vulnerability indicator vector, the weak area corresponding to each faulty line by using a golden section method and/or a secant iteration method includes:
if the value of the weakness index vector of the current fault line is 0, the current fault line does not contain the weakness area;
if the value of the weakness index vector of the current fault line is 1, constructing a first quadratic interpolation equation by using the falling amplitudes of the head point and the tail point of the current fault line and the falling amplitude of the middle point of the current fault line, calculating a first critical point by using the secant iteration method according to the root of the first quadratic interpolation equation, and determining the weak area contained in the current fault line; the number of roots of the first quadratic interpolation equation is 1, and the number of the first critical points is 1;
if the value of the weakness index vector of the current fault line is 1, solving a voltage equation corresponding to the current fault line by using the golden section method, acquiring a maximum drop amplitude value at a sensitive load access point corresponding to the current fault line, and judging whether the maximum drop amplitude value is greater than the voltage threshold value or not;
if so, the current fault line is the weak area;
if not, constructing a second quadratic interpolation equation by using the falling amplitudes of the head end point and the tail end point of the current fault line and the maximum falling amplitude, calculating a second critical point by using the secant iteration method according to the root of the second quadratic interpolation equation, and determining the weak area contained in the current fault line; the number of roots of the second quadratic interpolation equation is 2, and the number of the second critical points is 2.
Optionally, the solving, by using the golden section method, a voltage equation corresponding to the current faulty line to obtain a maximum drop amplitude at a sensitive load access point corresponding to the current faulty line includes:
determining a first preset point and a second preset point of the current fault line according to a golden ratio formula; wherein the formula of the golden ratio isThe first preset point isThe second preset point is Is the third preset point of the current faulty line,a fourth preset point of the current fault line;
calculating the dropping amplitude of the sensitive load access point caused by the faults of the first preset point and the second preset point according to a voltage equation corresponding to the current fault line; if the voltage equation corresponding to the current fault line is the voltage equation of the three-phase short-circuit fault, the drop amplitude at the sensitive load access point caused by the fault of the first preset pointAnd the drop amplitude at the sensitive load access point caused by the second preset point faultAre respectively asAndif the voltage equation corresponding to the current fault line is not the voltage equation of the three-phase short-circuit fault, thenIs composed of Andthe minimum value of (a) to (b),is composed ofAndminimum value of (1);
judging whether the drop amplitude of the sensitive load access point caused by the fault of the first preset point is larger than the drop amplitude of the sensitive load access point caused by the fault of the second preset point or not;
if the drop amplitude of the sensitive load access point caused by the fault of the first preset point is larger than the drop amplitude of the sensitive load access point caused by the fault of the second preset point, enabling the fault detection system to control the fault detection system to work in the fault detection systemAnd
if the drop amplitude of the sensitive load access point caused by the fault of the first preset point is not greater than the drop amplitude of the sensitive load access point caused by the fault of the second preset point, enabling the fault condition to be metAnd
judging whether the absolute value of the difference between the fourth preset point and the third preset point is smaller than a preset tolerance or not;
if the third preset point is subtracted from the fourth preset pointIf the absolute value of the difference of the preset points is smaller than the preset tolerance, the iteration is terminated, and the maximum drop amplitude at the sensitive load access point corresponding to the current fault line is obtained; wherein the maximum drop amplitude at the sensitive load access point corresponding to the current fault line is
And if the absolute value of the difference between the fourth preset point and the third preset point is not less than a preset tolerance, executing the voltage equation corresponding to the current fault line, and calculating the falling amplitude of the first preset point and the second preset point.
Optionally, the calculating a first critical point by using the cut-line iteration method according to the root of the first quadratic interpolation equation includes:
determining a first initial point and a second initial point according to the root of the first quadratic interpolation equation; the first initial point and the second initial point are respectively different points on the current fault line, and the distance between the first initial point and the root of the first quadratic interpolation equation is smaller than a distance threshold value;
by passingDetermining an estimation point of the current fault line; wherein,in order to be able to estimate the point,andrespectively the first initiation point and the second initiation point,andthe drop amplitudes at the sensitive load access point caused by the fault of the first initial point and the second initial point are respectively;
judging whether the difference obtained by subtracting the voltage threshold from the drop amplitude at the sensitive load access point caused by the fault of the estimation point is smaller than a preset tolerance or not;
if not, orderPerforming the passingDetermining an evaluation point;
if yes, the estimation point is the first critical point.
Optionally, before determining the weak area corresponding to each faulty line by using a golden section method and/or a secant iteration method according to the value of the vulnerability indicator vector, the method further includes:
and storing the corresponding relation between each fault line and the corresponding voltage equation and the drop amplitude at the sensitive load access point caused by the faults of the head end point and the tail end point of each fault line.
In addition, the invention also provides a device for identifying the weak area of the voltage sag of the power grid, which comprises the following components:
the selection module is used for selecting a corresponding voltage equation according to the acquired fault type of each fault line; the voltage equation is used for calculating the drop amplitude of the sensitive load access point caused by any fault on the corresponding fault line;
the calculation module is used for solving the dropping amplitude of the sensitive load access point caused by the faults of the head end point and the tail end point of each fault line according to the voltage equation and calculating the corresponding weakness index vector of each fault line; the numerical value of the weakness index vector is the relation between the corresponding fault line and the weak area;
and the determining module is used for determining the weak area corresponding to each fault line by utilizing a golden section method and/or a secant iteration method according to the numerical value of the weak index vector.
Optionally, the apparatus further comprises:
the power flow analysis module is used for calculating the voltage before the fault of each fault line through power flow analysis;
and the acquisition module is used for acquiring the sequence impedance matrix of each fault line by using the sequence admittance matrix.
The invention provides a method for identifying a weak area of power grid voltage sag, which comprises the following steps: selecting a corresponding voltage equation according to the acquired fault type of each fault line; the voltage equation is used for calculating the drop amplitude of the sensitive load access point caused by any fault on the corresponding fault line; solving the drop amplitude at the sensitive load access point caused by the faults of the head end point and the tail end point of each fault line according to a voltage equation, and calculating the corresponding weakness index vector of each fault line; the numerical value of the weak index vector is the relation between the corresponding fault line and the weak area; determining a weak area corresponding to each fault line by using a golden section method and/or a secant iteration method according to the numerical value of the weak index vector;
therefore, the method can calculate the dropping amplitude of the sensitive load access point caused by the fault of any point on each fault line by selecting the corresponding voltage equation according to the acquired fault type of each fault line; the number of critical points of each fault line can be obtained by calculating the corresponding weakness index vector of each fault line; the weak area corresponding to each fault line is determined by using the golden section method and/or the secant iteration method, and the critical point can be calculated by using a mixed method of the golden section method and the secant iteration method, so that the weak area of the power grid voltage sag is determined, the operation is less, the reference reliability is higher, the method can be effectively used for evaluating and analyzing the voltage sag performance of the power system, and the method has important significance for the high-quality production and operation of power customers. In addition, the invention also provides an identification device for the weak voltage sag area of the power grid, and the identification device has the beneficial effects.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
Fig. 1 is a flowchart of a method for identifying a weak area of a power grid voltage sag according to an embodiment of the present invention;
fig. 2 is a structural diagram of an identification apparatus for a weak area of grid voltage sag according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, fig. 1 is a flowchart illustrating a method for identifying a weak area of a grid voltage sag according to an embodiment of the present invention. The method can comprise the following steps:
step 101: selecting a corresponding voltage equation according to the acquired fault type of each fault line; the voltage equation is used for calculating the drop amplitude of the sensitive load access point caused by any fault on the corresponding fault line.
The faulty line in this step may be a line with a fault of a corresponding fault type, and the faulty line may be a line with a fault in the actual use process, and after the fault occurs in the actual use process of the line, the line is determined as the faulty line according to the method provided in the embodiment; the method provided by the embodiment may also be configured to set a line with a fault in the process of identifying the weak area of the voltage sag of the power grid, and the method provided by the embodiment further includes a step of setting a fault of a corresponding fault type for each line, so that each line becomes a corresponding fault line.
It can be understood that the purpose of this step may be to obtain a voltage equation for calculating the drop amplitude at the sensitive load access point caused by a fault at any point on the corresponding faulty line, through the fault type of each faulty line. The setting of the fault type and the voltage equation can be set by a designer, and the embodiment is not limited to any limitation as long as the drop amplitude at the sensitive load access point caused by any fault at any point on the fault line of the corresponding fault type, that is, the phase voltage amplitude at the sensitive load access point after the fault, can be calculated.
Specifically, a positive sequence impedance (Z) may be used1) Negative sequence impedance (Z)2) And zero sequence impedance (Z)0) The drop amplitude at the sensitive load access point caused by any fault on the fault line is calculated by the system impedance model of the three symmetrical components, and the step can be as follows: if the obtained fault class of the current fault lineIf the type is a phase-A single-phase earth fault, the selected voltage equation is as follows:andwherein s is a sensitive load access point of the current fault line,andphase voltage amplitudes of the A phase, the B phase and the C phase at the s point of the current fault line respectively,the voltage is the voltage before the fault at the s point of the current fault line;for the operation of a complex number, the operation is,the sequence voltage before the fault at the fault position K point of the current fault line is obtained;andrespectively positive, negative and zero sequence mutual impedance between the point s and the point K of the current fault line;andrespectively positive, negative and at the K point of the current fault lineZero sequence self-impedance;
if the fault type of the current fault line is a two-phase short-circuit fault of a B phase and a C phase, the selected voltage equation is as follows:and
if the fault type of the current fault line is a two-phase short circuit ground fault of a B phase and a C phase, the selected voltage equation is as follows: and
if the fault type of the current fault line is a three-phase short-circuit fault, the selected voltage equation is as follows:wherein,is the phase voltage amplitude at the s-point of the currently faulted line.
The current faulty line may be any faulty line among all faulty lines in this step.
It can be understood that, according to four fault types, namely, single-phase earth fault, two-phase short-circuit earth fault and three-phase short-circuit fault, the corresponding voltage equation can be selected to solve the fault line corresponding to the fault typeThe phase voltage magnitude at any point. If the fault type is three-phase short-circuit fault, the drop amplitude of any point on the fault line is phase voltage amplitudeIf the fault type is not three-phase short-circuit fault, the drop amplitude at the sensitive load access point caused by fault at any point (K) on the fault line is three-phase voltage amplitudeAndminimum value of (1).
It should be noted that for the above voltage equationAndcan be prepared by Andthese three equations are correspondingly derived. Wherein,is the driving point sequence impedance at the fault position K point,andrespectively the driving point sequence impedances of the head end point F and the tail end point T of the faulty line,is the transmission sequence impedance between the head end point F and the tail end point T of the faulty line,is the line sequence impedance between the head end point F and the tail end point T of the faulty line,is the transmission sequence impedance between any point s of the faulty line and the fault location K,is the transmission sequence impedance between the sensitive load access point s and the head end point F of the faulty line,is the transmission sequence impedance between the sensitive load access point s and the tail end point T of the faulty line,is the sequence voltage before failure at the failure location K,andthe sequence voltage before the fault of the head end point F and the tail end point T of the fault line is respectively, and p is the proportional length of the fault position K and the whole length of the fault line F-T (p is more than or equal to 0 and less than or equal to 1).
Correspondingly, in order to solve the above three formulas to obtain the voltage equation Andbefore using the corresponding voltage equation, that is, before step 102, calculating the voltage before fault of each fault line through power flow analysis may be further included; obtaining a sequence impedance matrix Z of each fault line by using a sequence admittance matrix012To obtain a pre-fault voltage and sequence impedance matrix Z of any point of each fault line012。
Step 102: solving the drop amplitude at the sensitive load access point caused by the faults of the head end point and the tail end point of each fault line according to a voltage equation, and calculating the corresponding weakness index vector of each fault line; and the numerical value of the weak index vector is the relation between the corresponding fault line and the weak area.
It can be understood that the value of the weakness indicator vector corresponding to each faulty line may be the number of critical points in the corresponding faulty line, that is, the relationship between the corresponding faulty line and the weak area. If the critical point does not exist in the fault line, the fault line does not contain the weak area; if a critical point exists in the fault line, the fault line comprises a weak area, namely one end of the fault line is in the weak area; if two critical points exist in the fault line, the fault line comprises two weak areas or is in the weak area, namely, two ends of the fault line are in the weak areas.
Specifically, the steps may be: according to a voltage equation corresponding to the current fault line, solving the drop amplitude at the sensitive load access point caused by the faults of the head end point and the tail end point of the current fault line; if the voltage equation corresponding to the current fault line is the voltage equation of the three-phase short-circuit fault, the head end point fault of the current fault line is introducedFall amplitude | F (F) at sensitive load access pointi) And the dip amplitude | f (T) at the sensitive load access point caused by tail-end fault of the currently faulty linei) I are respectivelyAndif the voltage equation corresponding to the current fault line is not the voltage equation of the three-phase short-circuit fault, then | F (F)i) Is |Andminimum value of, | f (T)i) Is |Andminimum value of, i is the current faulty line, FiFor the head end of the currently faulty line, TiThe tail end point of the current fault line;
respectively subtracting the difference of voltage thresholds from the drop amplitudes at the sensitive load access points caused by the faults of the head end point and the tail end point of the current fault line, and comparing the difference with 0 to determine that the weaknesses index vectors of the head end point and the tail end point of the current fault line are 0 or 1; wherein, the weakness index vector of the head end point of the current fault lineWeakness indicator vector for tail end point of current fault lineVthIs a voltageA threshold value;
adding the weakness index vectors of the head point and the tail point of the current fault line to determine the weakness index vector of the current fault line; wherein, the current fault line weakness index vector
It can be understood that, since the roll-off amplitudes at the sensitive load access points caused by the head end point and tail end point faults of each faulty line also need to be used in step 103, the roll-off amplitudes at the sensitive load access points caused by the head end point and tail end point faults of each faulty line obtained by the solution can be stored, and for the convenience of storing the roll-off amplitudes at the sensitive load access points caused by the head end point and tail end point faults of each faulty line and the calculation process in this step, the roll-off amplitudes at the head end point and tail end point of each faulty line in the form of a matrix can be obtained through the corresponding two roll-off amplitude vectors, for example,
two fall amplitudes ofAndwherein, Vmag,FDrop amplitude vector, V, at sensitive load access point caused by head end fault of each faulty linemag,TAnd (3) a dropping amplitude vector at a sensitive load access point caused by the fault of the tail end point of each fault line, wherein n is the number corresponding to all fault lines, and i represents that the current fault line is a positive integer which is greater than or equal to 1 and less than or equal to n.
Correspondingly, the weakness index vector of the head end point, the weakness index vector of the tail end point and the weakness index vector of each fault line are respectively Andwherein,
it should be noted that the weakness indicator vectors of the head end point and the tail end point of the current faulty line solved in the above mannerAndand may be 1 or 0, respectively. Corresponding weakness indicator vector LVI for currently faulty lineiWhich may be 0, 1 or 2, represents the number of critical points in the currently faulted line.
Step 103: and determining a weak area corresponding to each fault line by using a golden section method and/or a secant iteration method according to the numerical value of the weak index vector.
Specifically, in this step, if the value of the weakness index vector of the current faulty line is 0, the current faulty line does not include a weak area;
if the value of the weakness index vector of the current fault line is 1, constructing a first quadratic interpolation equation by using the falling amplitudes of the head point and the tail point of the current fault line and the falling amplitude of the middle point of the current fault line, calculating a first critical point by using a secant iteration method according to the root of the first quadratic interpolation equation, and determining a weak area contained in the current fault line; the number of roots of the first quadratic interpolation equation is 1, and the number of the first critical points is 1;
if the value of the weakness index vector of the current fault line is 1, solving a voltage equation corresponding to the current fault line by using a golden section method, acquiring a maximum drop amplitude value at a sensitive load access point corresponding to the current fault line, and judging whether the maximum drop amplitude value is greater than a voltage threshold value or not;
if yes, the current fault line is a weak area;
if not, constructing a second quadratic interpolation equation by using the falling amplitudes and the maximum falling amplitudes of the head point and the tail point of the current fault line, calculating a second critical point by using a secant iteration method according to the root of the second quadratic interpolation equation, and determining a weak area contained in the current fault line; the number of roots of the second quadratic interpolation equation is 2, and the number of the second critical points is 2.
The step of solving a voltage equation corresponding to the current faulty line by using a golden section method to obtain the maximum drop amplitude at the sensitive load access point corresponding to the current faulty line may include: determining a first preset point and a second preset point of the current fault line according to a golden ratio formula; wherein the formula of the golden ratio isThe first preset point isThe second preset point is Is the third preset point of the current faulty line,a fourth preset point of the current fault line;
calculating the dropping amplitude of the sensitive load access point caused by the faults of the first preset point and the second preset point according to a voltage equation corresponding to the current fault line; if the voltage equation corresponding to the current fault line is the voltage equation of the three-phase short-circuit fault, the drop amplitude at the sensitive load access point caused by the fault of the first preset pointAnd the drop amplitude at the sensitive load access point caused by the second preset point faultAre respectively asAndif the voltage equation corresponding to the current fault line is not the voltage equation of the three-phase short-circuit fault, thenIs composed of Andthe minimum value of (a) to (b),is composed ofAndminimum value of (1);
judging whether the drop amplitude of the sensitive load access point caused by the fault of the first preset point is larger than the drop amplitude of the sensitive load access point caused by the fault of the second preset point or not;
if the drop amplitude of the sensitive load access point caused by the fault of the first preset point is larger than the drop amplitude of the sensitive load access point caused by the fault of the second preset point, enabling the fault detection system to control the fault detection system to work in the fault detection systemAnd
if the drop amplitude of the sensitive load access point caused by the fault of the first preset point is not greater than the drop amplitude of the sensitive load access point caused by the fault of the second preset point, enabling the fault condition to be metAnd
judging whether the absolute value of the difference between the fourth preset point and the third preset point is smaller than a preset tolerance or not;
if the absolute value of the difference between the fourth preset point and the third preset point is smaller than a preset tolerance, terminating iteration and obtaining the maximum drop amplitude value of the sensitive load access point corresponding to the current fault line; wherein the maximum drop amplitude at the sensitive load access point corresponding to the current fault line is
And if the absolute value of the difference between the fourth preset point and the third preset point is not less than a preset tolerance, executing the voltage equation corresponding to the current fault line, and calculating the falling amplitude of the first preset point and the second preset point.
The step of calculating the first critical point by using a secant iteration method according to the root of the first quadratic interpolation equation may include:
determining a first initial point and a second initial point according to the root of the first quadratic interpolation equation; the first initial point and the second initial point are respectively different points on the current fault line, and the distance between the first initial point and the root of the first quadratic interpolation equation is smaller than a distance threshold value;
by passingDetermining an estimation point of a current fault line; wherein,in order to estimate the point(s),anda first initiation point and a second initiation point respectively,andrespectively are the falling amplitude values at the sensitive load access point caused by the faults of the first initial point and the second initial point;
judging whether the difference of the drop amplitude value at the sensitive load access point caused by the fault of the estimation point and the voltage threshold value is smaller than a preset tolerance or not;
if not, orderExecute throughDetermining an evaluation point;
if so, the estimated point is the first critical point.
It can be understood that, for the specific construction process and solution process of the first quadratic interpolation equation constructed by the dip amplitude at the sensitive load access point caused by the fault of the head end point and tail end point of the current fault line and the dip amplitude (| f (0.5) |) at the sensitive load access point caused by the fault of the middle point of the current fault line, and the second quadratic interpolation equation constructed by the dip amplitude and maximum dip amplitude at the sensitive load access point caused by the fault of the head end point and tail end point of the current fault line, a similar manner to the prior art can be adopted, and the embodiment is not limited in any way.
It should be noted that, for the process of calculating the second critical point by using the cut-line iteration method according to the root of the second quadratic interpolation equation, two points corresponding to the second critical point may be obtained in a manner similar to the step of calculating the first critical point by using the cut-line iteration method according to the root of the first quadratic interpolation equation.
It should be noted that, the purpose of this embodiment is to obtain the weak area corresponding to each faulty line, and for the current faulty line, after the weak area corresponding to the current faulty line is determined, the step of determining whether the weak areas corresponding to all faulty lines have been determined may be performed to ensure that the purpose of this embodiment can be achieved. Correspondingly, if the weak areas corresponding to all the fault lines are not determined, the next fault line is selected as the current fault line, and the weak area corresponding to the current fault line is determined. The present embodiment does not set any limit to this.
In the embodiment, the drop amplitude at the sensitive load access point caused by any fault point on each fault line can be calculated by selecting the corresponding voltage equation according to the acquired fault type of each fault line; the number of critical points of each fault line can be obtained by calculating the corresponding weakness index vector of each fault line; the weak area corresponding to each fault line is determined by using the golden section method and/or the secant iteration method, and the critical point can be calculated by using a mixed method of the golden section method and the secant iteration method, so that the weak area of the power grid voltage sag is determined, the operation is less, the reference reliability is higher, the method can be effectively used for evaluating and analyzing the voltage sag performance of the power system, and the method has important significance for the high-quality production and operation of power customers.
Referring to fig. 2, fig. 2 is a structural diagram of an identification apparatus for a weak area of grid voltage sag according to an embodiment of the present invention. The apparatus may include:
the selection module 100 is configured to select a corresponding voltage equation according to the acquired fault type of each fault line; the voltage equation is used for calculating the drop amplitude of the sensitive load access point caused by any fault on the corresponding fault line;
the calculating module 200 is configured to solve drop amplitudes at sensitive load access points caused by faults at the head end and the tail end of each faulty line according to the voltage equation, and calculate a corresponding weakness index vector of each faulty line; the numerical value of the weakness index vector is the relation between the corresponding fault line and the weak area;
the determining module 300 is configured to determine, according to the value of the weakness index vector, a weak region corresponding to each faulty line by using a golden section method and/or a secant iteration method.
Optionally, the apparatus may further include:
the power flow analysis module is used for calculating the voltage before the fault of each fault line through power flow analysis;
and the acquisition module is used for acquiring the sequence impedance matrix of each fault line by using the sequence admittance matrix.
In this embodiment, according to the acquired fault type of each fault line, the selection module 100 selects a corresponding voltage equation, and can calculate a drop amplitude at a sensitive load access point caused by a fault at any point on each fault line; the calculation module 200 calculates the weakness index vector corresponding to each fault line, so as to obtain the number of critical points of each fault line; the weak area corresponding to each fault line is determined by the determining module 300 by using a golden section method and/or a secant iteration method, and a critical point can be calculated by using a mixed method of the golden section method and the secant iteration method, so that the weak area of the power grid voltage sag is determined, the operation is less, the reference reliability is higher, the method can be effectively used for evaluating and analyzing the voltage sag performance of the power system, and the method has important significance for the high-quality production and operation of power customers.
The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. The device disclosed by the embodiment corresponds to the method disclosed by the embodiment, so that the description is simple, and the relevant points can be referred to the method part for description.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative components and steps have been described above generally in terms of their functionality in order to clearly illustrate this interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. A software module may reside in Random Access Memory (RAM), memory, Read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The method and the device for identifying the weak area of the voltage sag of the power grid provided by the invention are described in detail above. The principles and embodiments of the present invention are explained herein using specific examples, which are presented only to assist in understanding the method and its core concepts. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
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| CN119419792A (en) * | 2025-01-03 | 2025-02-11 | 国网吉林省电力有限公司吉林供电公司 | Power distribution system optimization operation method and system based on sensitive equipment loss |
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