CN113848421B - Voltage sag acquisition method and device considering transformer impedance voltage drop - Google Patents
Voltage sag acquisition method and device considering transformer impedance voltage drop Download PDFInfo
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Abstract
The invention discloses a voltage sag acquisition method and a device considering transformer impedance voltage drop, wherein the method comprises the following steps: acquiring three-phase voltage signals and three-phase current signals in the wave recording data of the voltage sag event at the high voltage side of the distribution transformer; acquiring the amplitude and the phase of three-phase fundamental wave voltage and the amplitude and the phase of three-phase fundamental wave current in the voltage sag event process; calculating a three-sequence component of the A-phase fundamental wave voltage and a three-sequence component of the A-phase fundamental wave current; obtaining the equivalent impedance sequence voltage drop of the transformer; acquiring voltage sequence components actually transmitted to a secondary side of the transformer; synthesizing voltage sequence components actually transmitted to the secondary side of the transformer to obtain three-phase voltage with voltage sag passing through the transformer; the invention has the advantages that: the voltage sag acquisition method considering the impedance voltage sag of the transformer is high in calculation accuracy, is favorable for obtaining the target point sag characteristic according to the existing monitoring point data, and provides data for user access point selection, voltage sag evaluation, positioning and the like.
Description
Technical Field
The invention relates to the technical field of power quality analysis methods, in particular to a voltage sag acquisition method and device considering impedance voltage drop of a transformer.
Background
Due to the influence of natural environment, weather, human factors and other factors, the problem of voltage sag caused by short circuit faults and other factors is unavoidable, which contradicts the current situation that industrial equipment tends to be integrated and refined, high-tech precision equipment with digital and informatization technology as a core is very sensitive to the voltage sag, and the voltage sag is further focused by power users, power grid companies and more research institutions and scholars due to the contradiction between the two.
The propagation of the voltage sag mainly comprises two links, namely propagation through a line and propagation through a transformer, wherein the propagation through the transformer is complex, the propagation is closely related to the type of sag, the connection mode of the transformer and the like, the voltage sag characteristics caused by different short-circuit fault types under the grounding mode of neutral points of different systems are greatly different, and the winding connection modes of different transformers influence the transmission of the voltage sag. The technical school of electrician 9, 22 nd volume 9, discloses the types of voltage sag under different grounding modes of neutral points and the transmission (one) among transformers in the literature, which mainly describes the grounding modes of the neutral points of the system, has great differences between the phase voltage and line voltage sag characteristics of the voltage class caused by short-circuit faults, analyzes the phase voltage and line voltage sag expressions of a neutral point effective grounding system and a non-effective grounding system by taking a single-phase grounding as an example, and the characteristics and types of the phase voltage and line voltage sag caused by two-phase grounding, two-phase short-circuit and three-phase short-circuit faults, and discusses the effectiveness of the characteristic expressions of the voltage sag types when considering the voltage phase jump, so as to further research the transmission rules of the sag types in transformers with different winding connection modes.
The prior expert scholars also analyze the transfer rules of different sag types through the primary transformer and the multi-stage transformer in detail, deduce the voltage sag amplitude values of different fault types transferred through the multi-stage transformers of different types, perform linear fitting on the voltage sag amplitude values, analyze the influence of different transformer winding connection groups on the voltage sag transfer rules, but the method is also limited to theoretical research, and does not perform verification of combination of theory and practice. The above-mentioned transfer rule is based on an ideal transformer, and the effect of the load current is not considered, but the existing literature recognizes that the load current has a certain influence on the voltage sag transfer characteristic, but does not deeply analyze the mechanism of the influence of the load current on the voltage sag transfer characteristic. The current power quality monitoring system monitors the power quality of monitoring points by using power quality monitoring terminals arranged on a power grid side or a user side, however, the power quality monitoring terminals of the power grid in China are limited in installation quantity, and a voltage sag observable area cannot cover the whole network, so that the research is based on the voltage sag transfer characteristic, a calculation method for the voltage sag of the power grid on the secondary side of the transformer is designed, the target point sag characteristic is obtained according to the current monitoring point data, and data is provided for user access point selection, voltage sag evaluation, positioning and the like, so that the foundation significance is great.
Disclosure of Invention
The technical problem to be solved by the invention is to provide the voltage sag acquisition method considering the impedance voltage drop of the transformer, which has high calculation accuracy, is favorable for obtaining the sag characteristics of the target point according to the data of the existing monitoring point, and provides data for user access point selection, voltage sag evaluation, positioning and the like.
The invention solves the technical problems by the following technical means: a voltage sag acquisition method taking into account a transformer impedance voltage drop, the method comprising:
step one: acquiring three-phase voltage signals and three-phase current signals in the wave recording data of the voltage sag event at the high voltage side of the distribution transformer;
Step two: the collected three-phase voltage signals and three-phase current signals are utilized to obtain the amplitude and the phase of the three-phase fundamental wave voltage and the amplitude and the phase of the three-phase fundamental wave current in the voltage sag event process;
Step three: according to a symmetrical component method, calculating a three-sequence component of the A-phase fundamental wave voltage and a three-sequence component of the A-phase fundamental wave current;
step four: obtaining the equivalent impedance sequence voltage drop of the transformer according to the equivalent impedance of the transformer and the three-sequence component of the A-phase fundamental wave current;
step five: obtaining a voltage sequence component actually transmitted to the secondary side of the transformer according to the three sequence components of the A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer;
step six: according to the symmetrical component method, voltage sequence components actually transmitted to the secondary side of the transformer are synthesized, and three-phase voltage after voltage sag passing through the transformer is obtained.
According to the invention, the transformer transformation ratio (i.e. coefficient matrix) and the transformer equivalent impedance voltage drop correction principle under ideal conditions are considered, so that the three-phase voltage of the voltage sag after passing through the transformer is obtained, the calculation accuracy is higher, the target point sag characteristic is obtained according to the existing monitoring point data, and data is provided for user access point selection, voltage sag evaluation, positioning and the like.
Further, the third step includes:
By the formula Acquiring three-order components of A-phase fundamental voltage, wherein K represents a coefficient matrix and/>Alpha=e j120°, j is a complex symbol,/>Representing the amplitude of the three-phase fundamental voltage,/>Representing the amplitude of the A-phase fundamental voltage,/>Representing the amplitude of the B-phase fundamental voltage,/>Representing the amplitude of the C-phase fundamental voltage;
By the formula Acquiring three-order components of A-phase fundamental current, wherein/>Representing the amplitude of three-phase fundamental current,/>Representing the amplitude of the phase A fundamental current,/>Representing the amplitude of the B-phase fundamental current,/>Representing the amplitude of the C-phase fundamental current.
Still further, the fourth step includes:
according to the three-sequence component of the equivalent impedance of the transformer sequence and the A-phase fundamental wave current, the formula is utilized
And obtaining the equivalent impedance sequence voltage drop of the transformer, wherein [ X T0 XT1 XT2 ] is the equivalent impedance of the transformer sequence.
Still further, the fifth step includes:
According to the three-sequence component of A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer, the formula is utilized
Obtaining a voltage sequence component actually transmitted to the secondary side of the transformer, wherein/>Represents the three-order component of the A-phase fundamental voltage and/>
Still further, the sixth step includes:
according to the symmetrical component method, the formula is utilized And synthesizing voltage sequence components actually transmitted to the secondary side of the transformer to obtain three-phase voltage after the voltage sag passes through the transformer, wherein H is a transmission rule of the voltage sag of the transformer under ideal conditions, and K -1 represents an inverse matrix of the coefficient matrix.
The invention also provides a voltage sag acquisition device considering the impedance voltage drop of the transformer, which comprises:
The first acquisition module is used for acquiring three-phase voltage signals and three-phase current signals in the wave recording data of the voltage sag event at the high voltage side of the distribution transformer;
The second acquisition module is used for obtaining the amplitude and the phase of the three-phase fundamental wave voltage and the amplitude and the phase of the three-phase fundamental wave current in the voltage sag event process by utilizing FFT (fast Fourier transform) on the acquired three-phase voltage signals and three-phase current signals;
The three-sequence component acquisition module is used for calculating the three-sequence component of the A-phase fundamental wave voltage and the three-sequence component of the A-phase fundamental wave current according to a symmetrical component method;
the equivalent impedance sequence voltage drop acquisition module is used for acquiring the equivalent impedance sequence voltage drop of the transformer according to the equivalent impedance of the transformer sequence and the three-sequence component of the A-phase fundamental wave current;
The actual voltage sequence component acquisition module is used for acquiring a voltage sequence component actually transmitted to the secondary side of the transformer according to the three sequence components of the A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer;
and the synthesis module is used for synthesizing voltage sequence components actually transmitted to the secondary side of the transformer according to a symmetrical component method to obtain three-phase voltage after the voltage sag passes through the transformer.
Further, the three-sequence component acquisition module is further configured to:
By the formula Acquiring three-order components of A-phase fundamental voltage, wherein K represents a coefficient matrix and/>Alpha=e j120°, j is a complex symbol,/>Representing the amplitude of the three-phase fundamental voltage,/>Representing the amplitude of the A-phase fundamental voltage,/>Representing the amplitude of the B-phase fundamental voltage,/>Representing the amplitude of the C-phase fundamental voltage;
By the formula Acquiring three-order components of A-phase fundamental current, wherein/>Representing the amplitude of three-phase fundamental current,/>Representing the amplitude of the phase A fundamental current,/>Representing the amplitude of the B-phase fundamental current,/>Representing the amplitude of the C-phase fundamental current.
Still further, the equivalent impedance sequence voltage drop acquisition module is further configured to:
according to the three-sequence component of the equivalent impedance of the transformer sequence and the A-phase fundamental wave current, the formula is utilized
And obtaining the equivalent impedance sequence voltage drop of the transformer, wherein [ X T0 XT1 XT2 ] is the equivalent impedance of the transformer sequence.
Still further, the actual voltage sequence component acquisition module is further configured to:
According to the three-sequence component of A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer, the formula is utilized
Obtaining a voltage sequence component actually transmitted to the secondary side of the transformer, wherein/>Represents the three-order component of the A-phase fundamental voltage and/>
Still further, the synthesis module is further configured to:
according to the symmetrical component method, the formula is utilized And synthesizing voltage sequence components actually transmitted to the secondary side of the transformer to obtain three-phase voltage after the voltage sag passes through the transformer, wherein H is a transmission rule of the voltage sag of the transformer under ideal conditions, and K -1 represents an inverse matrix of the coefficient matrix.
The invention has the advantages that: according to the invention, the transformer transformation ratio (i.e. coefficient matrix) and the transformer equivalent impedance voltage drop correction principle under ideal conditions are considered, so that the three-phase voltage of the voltage sag after passing through the transformer is obtained, the calculation accuracy is higher, the target point sag characteristic is obtained according to the existing monitoring point data, and data is provided for user access point selection, voltage sag evaluation, positioning and the like.
Drawings
Fig. 1 is a flowchart of a voltage sag obtaining method according to an embodiment of the present invention, which considers a transformer impedance voltage drop;
Fig. 2 is a schematic diagram of three-sequence components of a phase a fundamental voltage in a voltage sag process of a voltage sag obtaining method considering impedance voltage sag of a transformer according to an embodiment of the present invention;
fig. 3 is a schematic diagram of three-sequence components of a phase a fundamental current in a voltage sag process of a voltage sag obtaining method considering impedance voltage sag of a transformer according to an embodiment of the present invention;
Fig. 4 is a schematic diagram of equivalent impedance sequence voltage drop of a transformer in a voltage sag process of a voltage sag acquisition method considering impedance voltage drop of the transformer according to an embodiment of the present invention;
fig. 5 is a schematic diagram of voltage sequence components actually transmitted to a secondary side of a transformer in a voltage sag obtaining method considering impedance voltage drop of the transformer according to an embodiment of the present invention;
Fig. 6 is a schematic diagram of a trend of an effective value of a phase a voltage on a high-voltage side and a low-voltage side of a transformer in a voltage sag obtaining method considering impedance voltage drop of the transformer according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions in the embodiments of the present invention will be clearly and completely described in the following in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
As shown in fig. 1, a voltage sag acquisition method considering a transformer impedance voltage drop, the method comprising:
S1: acquiring three-phase voltage signals { u A(n);uB(n);uC (n) } and three-phase current signals { i A(n);iB(n);iC (n) } in the high-voltage side voltage sag event wave-recording data of the distribution transformer by an online monitoring device; in this embodiment, A single-phase ground fault occurs in A high-voltage side A phase of the transformer, the type of the transformer is I-class, the connection mode Ynyn of the transformer, and the sequence impedance of the transformer is [35.49 35.49 28.39] Ω.
S2: the acquired three-phase voltage signal { U A(n);uB(n);uC (n) } and three-phase current signal { I A(n);iB(n);iC (n) } are utilized to obtain the amplitude { U A;UB;UC } and the phase { P UA;PUB;PUC } of the three-phase fundamental wave voltage, and the amplitude { I A;IB;IC } and the phase { P IA;PIB;PIC } of the three-phase fundamental wave current in the voltage sag event process by utilizing fast Fourier transform FFT;
s3: according to a symmetrical component method, calculating a three-sequence component of the A-phase fundamental wave voltage and a three-sequence component of the A-phase fundamental wave current; the specific process is as follows:
By the formula Acquiring three-order components of A-phase fundamental voltage, wherein K represents a coefficient matrix and/>Alpha=e j120°, j is a complex symbol,/>Representing the amplitude of the three-phase fundamental voltage,/>Representing the amplitude of the A-phase fundamental voltage,/>Representing the amplitude of the B-phase fundamental voltage,/>Representing the amplitude of the C-phase fundamental voltage;
By the formula Acquiring three-order components of A-phase fundamental current, wherein/>Representing the amplitude of three-phase fundamental current,/>Representing the amplitude of the phase A fundamental current,/>Representing the amplitude of the B-phase fundamental current,/>Representing the amplitude of the C-phase fundamental current. As shown in fig. 2, the three-sequence component of the a-phase fundamental voltage during the voltage sag refers to positive sequence, negative sequence and zero sequence, and as shown in fig. 3, the three-sequence component of the a-phase fundamental current during the voltage sag is shown in per unit value.
S4: obtaining the equivalent impedance sequence voltage drop of the transformer according to the equivalent impedance of the transformer and the three-sequence component of the A-phase fundamental wave current; the specific process is as follows:
according to the three-sequence component of the equivalent impedance of the transformer sequence and the A-phase fundamental wave current, the formula is utilized
And obtaining the equivalent impedance sequence voltage drop of the transformer, wherein [ X T0 XT1 XT2 ] is the equivalent impedance of the transformer sequence. Fig. 4 is a schematic diagram of the equivalent impedance sequence voltage drop of the transformer in the voltage sag process.
S5: obtaining a voltage sequence component actually transmitted to the secondary side of the transformer according to the three sequence components of the A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer; the specific process is as follows:
According to the three-sequence component of A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer, the formula is utilized
Obtaining a voltage sequence component actually transmitted to the secondary side of the transformer, wherein/>Represents the three-order component of the A-phase fundamental voltage and/>Fig. 5 is a schematic diagram of the voltage sequence component actually transmitted to the secondary side of the transformer.
S6: according to the symmetrical component method, voltage sequence components actually transmitted to the secondary side of the transformer are synthesized to obtain three-phase voltage after voltage sag passing through the transformer, and the specific process is as follows:
according to the symmetrical component method, the formula is utilized And synthesizing voltage sequence components actually transmitted to the secondary side of the transformer to obtain three-phase voltage after the voltage sag passes through the transformer, wherein H is a transmission rule of the voltage sag of the transformer under ideal conditions, and K -1 represents an inverse matrix of the coefficient matrix. As shown in fig. 6, the trend of the voltage of the phase a on the high and low voltage sides of the transformer is shown, and the trend of the voltage of the phase B and the voltage of the phase C are not shown.
According to the technical scheme, the transformer voltage sag transmission rule under ideal conditions of transformer transformation ratio (namely coefficient matrix) and transformer equivalent impedance voltage drop correction is considered, the three-phase voltage after the voltage sag passes through the transformer is obtained, calculation accuracy is higher, the target point sag characteristic is obtained according to the existing monitoring point data, and data are provided for user access point selection, voltage sag evaluation, positioning and the like.
Example 2
Based on embodiment 1 of the present invention, embodiment 2 of the present invention further provides a voltage sag obtaining device considering impedance voltage drop of a transformer, the device comprising:
The first acquisition module is used for acquiring three-phase voltage signals and three-phase current signals in the wave recording data of the voltage sag event at the high voltage side of the distribution transformer;
The second acquisition module is used for obtaining the amplitude and the phase of the three-phase fundamental wave voltage and the amplitude and the phase of the three-phase fundamental wave current in the voltage sag event process by utilizing FFT (fast Fourier transform) on the acquired three-phase voltage signals and three-phase current signals;
The three-sequence component acquisition module is used for calculating the three-sequence component of the A-phase fundamental wave voltage and the three-sequence component of the A-phase fundamental wave current according to a symmetrical component method;
the equivalent impedance sequence voltage drop acquisition module is used for acquiring the equivalent impedance sequence voltage drop of the transformer according to the equivalent impedance of the transformer sequence and the three-sequence component of the A-phase fundamental wave current;
The actual voltage sequence component acquisition module is used for acquiring a voltage sequence component actually transmitted to the secondary side of the transformer according to the three sequence components of the A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer;
and the synthesis module is used for synthesizing voltage sequence components actually transmitted to the secondary side of the transformer according to a symmetrical component method to obtain three-phase voltage after the voltage sag passes through the transformer.
Specifically, the three-sequence component acquisition module is further configured to:
By the formula Acquiring three-order components of A-phase fundamental voltage, wherein K represents a coefficient matrix and/>Alpha=e j120°, j is a complex symbol,/>Representing the amplitude of the three-phase fundamental voltage,/>Representing the amplitude of the A-phase fundamental voltage,/>Representing the amplitude of the B-phase fundamental voltage,/>Representing the amplitude of the C-phase fundamental voltage;
By the formula Acquiring three-order components of A-phase fundamental current, wherein/>Representing the amplitude of three-phase fundamental current,/>Representing the amplitude of the phase A fundamental current,/>Representing the amplitude of the B-phase fundamental current,/>Representing the amplitude of the C-phase fundamental current.
More specifically, the equivalent impedance sequence voltage drop acquisition module is further configured to:
according to the three-sequence component of the equivalent impedance of the transformer sequence and the A-phase fundamental wave current, the formula is utilized
And obtaining the equivalent impedance sequence voltage drop of the transformer, wherein [ X T0 XT1 XT2 ] is the equivalent impedance of the transformer sequence.
More specifically, the actual voltage sequence component acquisition module is further configured to:
According to the three-sequence component of A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer, the formula is utilized
Obtaining a voltage sequence component actually transmitted to the secondary side of the transformer, wherein/>Represents the three-order component of the A-phase fundamental voltage and/>
More specifically, the synthesis module is further configured to:
according to the symmetrical component method, the formula is utilized And synthesizing voltage sequence components actually transmitted to the secondary side of the transformer to obtain three-phase voltage after the voltage sag passes through the transformer, wherein H is a transmission rule of the voltage sag of the transformer under ideal conditions, and K -1 represents an inverse matrix of the coefficient matrix.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (4)
1. A voltage sag acquisition method taking into account a transformer impedance voltage drop, the method comprising:
step one: acquiring three-phase voltage signals and three-phase current signals in the wave recording data of the voltage sag event at the high voltage side of the distribution transformer;
Step two: the collected three-phase voltage signals and three-phase current signals are utilized to obtain the amplitude and the phase of the three-phase fundamental wave voltage and the amplitude and the phase of the three-phase fundamental wave current in the voltage sag event process;
Step three: according to a symmetrical component method, calculating a three-sequence component of the A-phase fundamental wave voltage and a three-sequence component of the A-phase fundamental wave current;
Step four: obtaining the equivalent impedance sequence voltage drop of the transformer according to the equivalent impedance of the transformer and the three-sequence component of the A-phase fundamental wave current; according to the three-sequence component of the equivalent impedance of the transformer sequence and the A-phase fundamental wave current, the formula is utilized
Obtaining the equivalent impedance sequence voltage drop of the transformer, wherein [ X T0 XT1 XT2 ] is the equivalent impedance of the transformer sequence;
Step five: obtaining a voltage sequence component actually transmitted to the secondary side of the transformer according to the three sequence components of the A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer; according to the three-sequence component of A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer, the formula is utilized
Obtaining a voltage sequence component actually transmitted to the secondary side of the transformer, wherein/>Represents the three-order component of the A-phase fundamental voltage and/>
Step six: according to a symmetrical component method, synthesizing voltage sequence components actually transmitted to the secondary side of the transformer to obtain three-phase voltage after voltage sag passing through the transformer; the specific process is as follows: according to the symmetrical component method, the formula is utilizedAnd synthesizing voltage sequence components actually transmitted to the secondary side of the transformer to obtain three-phase voltage after the voltage sag passes through the transformer, wherein H is a transmission rule of the voltage sag of the transformer under ideal conditions, and K -1 represents an inverse matrix of the coefficient matrix.
2. The method for obtaining a voltage sag taking into account a voltage drop across a transformer impedance of claim 1, wherein said step three comprises:
By the formula Acquiring three-order components of A-phase fundamental voltage, wherein K represents a coefficient matrix and/>Alpha=e j120°, j is a complex symbol,/>Representing the amplitude of the three-phase fundamental voltage,/>Representing the amplitude of the A-phase fundamental voltage,/>Representing the amplitude of the B-phase fundamental voltage,/>Representing the amplitude of the C-phase fundamental voltage;
By the formula Three-sequence components of a-phase fundamental current are acquired, wherein,Representing the amplitude of three-phase fundamental current,/>Representing the amplitude of the phase A fundamental current,/>Representing the amplitude of the B-phase fundamental current,Representing the amplitude of the C-phase fundamental current.
3. A voltage sag acquisition device that accounts for a transformer impedance voltage drop, the device comprising:
The first acquisition module is used for acquiring three-phase voltage signals and three-phase current signals in the wave recording data of the voltage sag event at the high voltage side of the distribution transformer;
The second acquisition module is used for obtaining the amplitude and the phase of the three-phase fundamental wave voltage and the amplitude and the phase of the three-phase fundamental wave current in the voltage sag event process by utilizing FFT (fast Fourier transform) on the acquired three-phase voltage signals and three-phase current signals;
The three-sequence component acquisition module is used for calculating the three-sequence component of the A-phase fundamental wave voltage and the three-sequence component of the A-phase fundamental wave current according to a symmetrical component method;
the equivalent impedance sequence voltage drop acquisition module is used for acquiring the equivalent impedance sequence voltage drop of the transformer according to the equivalent impedance of the transformer sequence and the three-sequence component of the A-phase fundamental wave current; the equivalent impedance sequence voltage drop acquisition module is also used for:
according to the three-sequence component of the equivalent impedance of the transformer sequence and the A-phase fundamental wave current, the formula is utilized
Obtaining the equivalent impedance sequence voltage drop of the transformer, wherein [ X T0 XT1 XT2 ] is the equivalent impedance of the transformer sequence;
The actual voltage sequence component acquisition module is used for acquiring a voltage sequence component actually transmitted to the secondary side of the transformer according to the three sequence components of the A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer; the actual voltage sequence component acquisition module is further configured to:
According to the three-sequence component of A-phase fundamental wave voltage and the equivalent impedance sequence voltage drop of the transformer, the formula is utilized
Obtaining a voltage sequence component actually transmitted to the secondary side of the transformer, wherein/>Represents the three-order component of the A-phase fundamental voltage and/>
The synthesis module is used for synthesizing voltage sequence components actually transmitted to the secondary side of the transformer according to a symmetrical component method to obtain three-phase voltage after the voltage sag passes through the transformer, and is also used for:
according to the symmetrical component method, the formula is utilized And synthesizing voltage sequence components actually transmitted to the secondary side of the transformer to obtain three-phase voltage after the voltage sag passes through the transformer, wherein H is a transmission rule of the voltage sag of the transformer under ideal conditions, and K -1 represents an inverse matrix of the coefficient matrix.
4. A voltage sag acquisition device according to claim 3, wherein the three-sequence component acquisition module is further configured to:
By the formula Acquiring three-order components of A-phase fundamental voltage, wherein K represents a coefficient matrix and/>Alpha=e j120°, j is a complex symbol,/>Representing the amplitude of the three-phase fundamental voltage,/>Representing the amplitude of the A-phase fundamental voltage,/>Representing the amplitude of the B-phase fundamental voltage,/>Representing the amplitude of the C-phase fundamental voltage;
By the formula Three-sequence components of a-phase fundamental current are acquired, wherein,Representing the amplitude of three-phase fundamental current,/>Representing the amplitude of the phase A fundamental current,/>Representing the amplitude of the B-phase fundamental current,/>Representing the amplitude of the C-phase fundamental current.
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