CN111856321A - Three-phase transformer short-circuit parameter online monitoring method based on fundamental wave positive sequence component - Google Patents

Abstract

The invention discloses a three-phase transformer short-circuit parameter online monitoring method based on fundamental wave positive sequence components, which comprises the following steps: firstly, constructing a monitoring model for extracting fundamental wave sequence components of each input signal; secondly, the constructed monitoring model is placed in a power grid circuit of the three-phase transformer, so that the power grid voltage of the three-phase transformer firstly passes through the monitoring model; then, the fundamental component and the fundamental orthogonal component of the power grid voltage of the three-phase transformer passing through the monitoring model are extracted firstly, and then the fundamental sequence component can be extracted through the transformation matrix. According to the invention, the short-circuit impedance value of the three-phase transformer can be accurately monitored on line, the traditional off-line monitoring method cannot realize real-time monitoring, the accurate detection of the short-circuit impedance value can enable the operation analysis of the three-phase transformer to be more accurate and reliable, and the accurate short-circuit impedance value is beneficial to timely finding out the three-phase transformer with deformed windings and carrying out predictive maintenance on the three-phase transformer.

Description

Three-phase transformer short-circuit parameter online monitoring method based on fundamental wave positive sequence component

Technical Field

The invention relates to the technical field of on-line monitoring of three-phase transformers, in particular to a three-phase transformer short-circuit parameter on-line monitoring method based on fundamental wave positive sequence components.

Background

The transformer plays an important role in a power system, bears the task of mutual exchange between electric energy of different voltage grades, can directly influence the reliability and stability of power supply by normal work, and is difficult to avoid faults and accidents of the transformer which runs for a long time in a network connection mode, so that the transformer has important significance for real-time detection of the running state and the health condition of the transformer.

Among various faults of the transformer, winding faults of the transformer are more common and become one of the faults with the highest occurrence frequency of the transformer. However, the diagnosis of the transformer winding is mainly performed by an offline method such as a frequency response method, an impedance analysis method and a low-voltage pulse method, so that the winding fault of the transformer cannot be found in time, and the real-time monitoring of the short-circuit parameter cannot be realized.

Disclosure of Invention

The invention aims to provide an online monitoring method for a short-circuit parameter of a three-phase transformer based on a fundamental positive sequence component, so as to solve the problems in the background technology.

In order to achieve the purpose, the invention provides the following technical scheme:

the three-phase transformer short-circuit parameter on-line monitoring method based on the fundamental wave positive sequence component comprises the following steps:

firstly, constructing a monitoring model for extracting fundamental wave sequence components of each input signal;

secondly, the constructed monitoring model is placed in a power grid circuit of the three-phase transformer, so that the power grid voltage of the three-phase transformer firstly passes through the monitoring model;

then, the fundamental component and the fundamental orthogonal component of the power grid voltage of the three-phase transformer passing through the monitoring model are extracted firstly, and then the fundamental sequence component can be extracted through a transformation matrix;

and finally, obtaining a short-circuit impedance value of the three-phase transformer according to the extracted fundamental sequence component, and comparing the obtained short-circuit impedance value with a standard impedance value to judge whether the winding of the three-phase transformer is deformed.

Further, the monitoring model is a multiple second-order generalized integrator-frequency locking loop.

Compared with the prior art, the invention has the beneficial effects that:

1. the method can accurately monitor the short-circuit impedance value of the three-phase transformer on line, and the traditional off-line monitoring method cannot realize real-time monitoring.

2. The accurate detection of the short-circuit impedance value can make the operation analysis of the three-phase transformer more accurate and reliable.

3. The accurate short-circuit impedance value is helpful for timely finding out the three-phase transformer with deformed windings and carrying out predictive maintenance on the three-phase transformer.

Drawings

FIG. 1 is a fundamental sequence component extraction schematic block diagram in a fundamental positive sequence component-based three-phase transformer short-circuit parameter online monitoring method;

FIG. 2 is a transformer winding model in the online monitoring method for the short-circuit parameters of the three-phase transformer based on the fundamental positive sequence component;

FIG. 3 is a positive sequence equivalent circuit diagram of a transformer in the three-phase transformer short-circuit parameter on-line monitoring method based on the fundamental positive sequence component;

FIG. 4 is a schematic diagram of the orientation of the phasor of the primary voltage of the d-axis in the online monitoring method of the short-circuit parameter of the three-phase transformer based on the fundamental positive sequence component;

fig. 5 is a phasor diagram of the d-axis primary voltage orientation in the three-phase transformer short-circuit parameter online monitoring method based on the fundamental positive sequence component.

Detailed Description

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 only a part of the embodiments of the present invention, and not all of the embodiments. 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. 1-5, the present invention provides a technical solution:

the three-phase transformer short-circuit parameter on-line monitoring method based on the fundamental wave positive sequence component comprises the following steps:

step S101, firstly, constructing a monitoring model for extracting fundamental wave sequence components of each input signal;

step S103, secondly, placing the constructed monitoring model in a power grid circuit of the three-phase transformer, so that the power grid voltage of the three-phase transformer firstly passes through the monitoring model;

and step S105, firstly, extracting fundamental wave components and fundamental wave orthogonal components of the grid voltage of the three-phase transformer passing through the monitoring model, and then, extracting fundamental wave sequence components through a transformation matrix.

And S107, finally, obtaining the short-circuit impedance value of the three-phase transformer according to the extracted fundamental sequence component, and comparing the obtained short-circuit impedance value with a standard impedance value to judge whether the winding of the three-phase transformer is deformed.

The fundamental sequence component extraction method based on the monitoring model (MSOGI-FLL) can accurately and quickly realize the extraction of the fundamental sequence component under the condition of unbalanced power grid or harmonic interference, and the structure is relatively simple and is easy to realize in engineering practice, so that the monitoring model is preferably a multiple second-order generalized integrator-frequency locked loop in the embodiment.

The principle of the transformation matrix in this embodiment is:

in the formula, the positive sequence component is represented by a "+" superscript, the negative sequence component is represented by a "-" superscript, and the zero sequence component is represented by a "0" superscript.

For convenience of explanation, the following three-phase transformer using the delta/YN connection is exemplified:

the winding model is as follows, and the phasor equation expression of the primary winding and the secondary winding can be obtained according to the mathematical model:

in the formula

The phase voltage of each winding on the triangle side of the primary side of the transformer,

the values of the voltages of the windings on the star side of the secondary side are integrated,

the phase currents of the windings of each phase on the triangle side of the primary side,

the values of the phase currents of the windings on the star side of the secondary side are calculated,

and

respectively, the electromotive forces generated in the primary and secondary windings by the main flux.

Since the phase current of the primary side triangular side winding cannot be directly measured, it needs to be represented by using the relationship between the line and the phase current, and according to the transformer winding model in example (2), the relationship can be obtained by using kirchhoff's current law:

the formula (4) is arranged and the internal circulating current of the triangular side winding is considered

The expression of the triangle side phase current can be obtained:

the formula (5) is substituted into the formula (2) to finally obtain a primary phasor equation expression as shown in the formula (6):

The MSOGI-FLL can be used for respectively obtaining fundamental positive sequence components of primary phase voltage and phase current of the transformer

Fundamental positive sequence component of secondary side phase voltage and phase current

The T-type equivalent circuit for analyzing the symmetric operation of the transformer is also applicable to the positive sequence system of the transformer, and the positive sequence equivalent circuit of the transformer is shown in fig. 3. And (3) arranging according to the positive sequence equivalent circuit of the transformer to obtain a phasor equation of the positive sequence component:

the primary and secondary side voltages and current phasors of the three-phase transformer can be converted into a synchronous rotating coordinate system with directional d-axis primary side voltage phasors by utilizing alpha beta/dq conversion, as shown in fig. 4. After the primary voltage phasor of the d axis is oriented, the primary and secondary voltage phasors and the current phasor of the transformer can obtain corresponding quantities under a dq rotating coordinate system through alpha beta/dq transformation:

wherein, the sine and cosine values of the included angle between the d axis and the alpha axis are as follows:

converting the formula (7) into a form under a dq rotating coordinate system, and obtaining the relation between each positive sequence component of the primary side and the secondary side of the transformer and the short-circuit parameter of the transformer:

the transformer phasor diagram for the d-axis primary voltage orientation obtained from equation (10) is shown in fig. 5. The matrix expression for rewriting the equation (10) to the transformer short-circuit parameter is shown in equation (11), where the primary resistance and the leakage inductance of the transformer are considered to be equal to the reduced values of the secondary resistance and the leakage inductance:

A series of matrix operations are performed on the formula (11), and finally, the short-circuit parameter expression can be obtained:

and comparing the obtained short circuit impedance value with an industry standard impedance value to judge the deformation condition of the winding.

It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.

Claims (2)

1. The three-phase transformer short-circuit parameter on-line monitoring method based on the fundamental wave positive sequence component is characterized by comprising the following steps of:

firstly, constructing a monitoring model for extracting fundamental wave sequence components of each input signal;

secondly, the constructed monitoring model is placed in a power grid circuit of the three-phase transformer, so that the power grid voltage of the three-phase transformer firstly passes through the monitoring model;

then, the fundamental component and the fundamental orthogonal component of the power grid voltage of the three-phase transformer passing through the monitoring model are extracted firstly, and then the fundamental sequence component can be extracted through a transformation matrix;

and finally, obtaining a short-circuit impedance value of the three-phase transformer according to the extracted fundamental sequence component, and comparing the obtained short-circuit impedance value with a standard impedance value to judge whether the winding of the three-phase transformer is deformed.

2. The on-line monitoring method for the short-circuit parameter of the three-phase transformer based on the fundamental positive sequence component of claim 1 is characterized in that: the monitoring model is a multiple second-order generalized integrator-frequency locking ring.

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