阅读说明：本技术 一种自适应变压器涌流抑制方法 (Adaptive transformer inrush current suppression method ) 是由 马迎东 韩宝军 焦立波 高利平 于 2020-11-25 设计创作，主要内容包括：本申请公开了一种自适应变压器涌流抑制方法,旨在通过控制变压器合闸角度来抑制励磁涌流,降低因涌流过大对变压器本体造成损坏的目的。本发明首先通过采集变压器断路器分闸时刻角度,获取变压器各相剩磁幅值、极性关系,然后将各相剩磁与电源侧各相磁通组成数学模型,以寻求变压器最佳合闸角度,最后,根据实际合闸角和最佳合闸角偏差,调整剩磁峰值系数,优化变压器分闸后各相剩磁,以保证变压器在最佳合闸角合闸时涌流抑制效果最佳。本发明利用图形分析法,可直观明了找到最佳合闸相位规律,具有普遍适应性,可以实现变压器合闸时各相涌流最优,避免涌流分布不均情况,同时可以实现自适应剩磁优化,任意相快速合闸。(The application discloses a method for suppressing inrush current of a self-adaptive transformer, which aims to suppress excitation inrush current by controlling the switching-on angle of the transformer and reduce the damage to a transformer body caused by excessive inrush current. According to the method, the relation between the amplitude and the polarity of each phase of residual magnetism of the transformer is obtained by collecting the opening moment angle of the breaker of the transformer, then the residual magnetism of each phase and the magnetic flux of each phase at the power supply side form a mathematical model to seek the optimal closing angle of the transformer, and finally, the residual magnetism peak value coefficient of each phase after the opening of the transformer is adjusted according to the deviation of the actual closing angle and the optimal closing angle, so that the inrush current suppression effect of the transformer is optimal when the transformer is closed at the optimal closing angle. The method can intuitively and clearly find the optimal switching-on phase rule by utilizing a graphic analysis method, has general adaptability, can realize the optimal inrush current of each phase when the transformer is switched on, avoids the condition of uneven distribution of the inrush current, and can realize self-adaptive remanence optimization and rapid switching-on of any phase.)

1. An adaptive transformer inrush current suppression method is characterized by comprising the following steps:

s1, acquiring the opening time angle of the transformer breaker;

s2, calculating the relation between the residual magnetic amplitude and the polarity of each phase of the transformer according to the opening angle of each phase;

s3, forming a mathematical model by the residual magnetism of each phase and the three-phase magnetic flux on the power supply side;

s4, seeking the optimal closing angle of the transformer and performing closing operation;

and S5, according to the deviation between the optimal closing angle and the actual closing angle, optimizing the remanence peak coefficient to prepare for the next closing.

2. The adaptive transformer inrush current suppression method of claim 1, wherein: in S1, the transformer is at t_opnAnd (3) switching off at the moment, wherein the phase of the corresponding A-phase voltage is alpha, and then the three-phase residual magnetism of the transformer corresponding to the switching off at the moment can be obtained by using a voltage integration method, wherein the three-phase residual magnetism respectively comprises the following steps:

wherein phi_Ar、Φ_Br、Φ_CrAre respectively a transformer t_opnAt the moment A, B, C, the three-phase remanence, K value is the peak coefficient of single-phase remanence, and phi is taken when the switch is first switched on_m(iron core magnetic flux amplitude when the transformer operates stably), the value can be optimized gradually through actual phase angle deviation after multiple switchovers in the scheme, and the value is constant before each switchon.

3. The adaptive transformer inrush current suppression method of claim 2, wherein: three-phase remanence needs to meet the following requirements: phi_Ar+Φ_Br+Φ_Cr＝0。

4. The adaptive transformer inrush current suppression method of claim 1, wherein: the S3 is a mathematical model of the resulting data in S2 and the expected flux of the system.

5. The adaptive transformer inrush current suppression method of claim 4, wherein: setting: the power supply side A phase voltage is U_A(t)＝U_msin (ω t), because the expected flux lags the corresponding phase voltage by 90,

then there is

Wherein phi_A(t)、Φ_B(t)、Φ_C(t)Respectively three-phase expected flux of power supply side_mFor the core flux amplitude when the transformer is in stable operation, the dynamic flux of a certain phase (taking phase a as an example) of the transformer can be expressed as:

wherein phi_mSaturated magnetic flux,The initial phase angle and the decay time constant of tau of the primary side A phase voltage are obtained, R, L the total resistance and total inductance tau of the single-phase loop of the transformer are equal to L/R, whenDuring the process, the transient magnetic flux in the transformer core can be eliminated and directly enters a steady state, at the moment, the excitation inrush current cannot be generated, the sine wave with the difference of three-phase voltage angles of A, B, C degrees is arranged on the actual power supply side, the transient magnetic flux of each phase is balanced, and according to the formula (4), when the expected magnetic flux is closer to the residual magnetism, the smaller the transient magnetic flux is, one transient magnetic flux is required to beThe value is such that in the following three formulae Δ Φ_A、ΔΦ_C、ΔΦ_CSimultaneously, the requirements of minimum and three-phase numerical balance are met:

the above-described absolute value mathematical model can be converted into a problem of the expected flux to corresponding phase remanence distance.

6. The adaptive transformer inrush current suppression method of claim 5, wherein: the graphic analysis method comprises the following steps:

(1) establishing X/Y axis with (0.0) point as center and phi_mDrawing a circle by radius, marking three residual magnetizations phi with the ordinate of three phases on the circle_Ar、Φ_Br、Φ_CrIs assumed to have a value of |. phi_Ar|>|Φ_Br|>|Φ_Cr|。

(2) Since the equation of the circle can be combined and_Ar|>|Φ_Br|>|Φ_Cri, then remanence Φ_Ar、Φ_BrThe coordinates on the circle can be found: a1 and B1 are connected with each other, the C1 point where the perpendicular bisector intersects with the circle is used as a C-phase initial closing angle, and at the moment, the A, B-phase initial phase angle can also be known;

(3) when C1 goes to phi_CrIs less than or equal to B1 to phi_BrSwitching on according to the initial phase angle; when C1 goes to phi_CrIs greater than B1 to phi_BrIs shifted by the minimum angle theta from the initial phase angle to C1 to phi_CrIs equal to B1 to phi_BrA distance of 1/2 (Y)_C1-Y_B1) At this time, the angle corresponding to the distance is the final closing angle (to simplify the calculation, the distance problem can be converted into the inner angle problem).

7. The adaptive transformer inrush current suppression method of claim 6, wherein: when the remanence of the three phases is not 0, two optimal closing angles exist in the phase with the minimum remanence amplitude, and the deviation of the two angles is not 180 degrees; when the remanence of at least one phase of the three phases is 0, the phase difference of two optimal closing angles corresponding to the remanence of 0 is 180 degrees.

8. The adaptive transformer inrush current suppression method of claim 6, wherein: when the remanence of one phase is 0, the optimal closing angle is the angle corresponding to the remanence of 0, namely k pi, and other phases rotate 120 degrees clockwise and anticlockwise correspondingly on the basis that the remanence of the other phases is 0.

9. The adaptive transformer inrush current suppression method of claim 1, wherein: in the step S5, when the closing angle has a deviation from the actual closing angle, optimizing the K value and adjusting the residual magnetism value; when the actual closing angle is ahead of the optimal closing angle, increasing the K value, namely simultaneously increasing the three-phase remanence value; and when the actual closing angle lags behind the optimal closing angle, reducing the K value, enabling the closing angle to be equal to the actual closing angle through adjustment, and recording the residual magnetism calculation coefficient of the K value for residual magnetism evaluation before the next closing (the current opening).

10. The adaptive transformer inrush current suppression method of claim 9, wherein: and selecting an optimal closing angle according to the remanence amplitude minimum phase in the remanence of each phase before the transformer is closed as a closing reference phase, and realizing the optimization of the next closing angle through the K value by selecting the optimal closing angle according to the corresponding remanence distance (internal angle) of the system.

Technical Field

The application relates to the technical field of power transformers, in particular to a self-adaptive transformer inrush current suppression method.

Background

The power transformer is a very important device in the power system, and the importance of the power transformer is directly related to the safe and stable operation of the whole power system. If the transformer is damaged, the overhaul difficulty is high, the period is long, the safe operation of a power grid is influenced, even economic loss and social influence which are difficult to estimate can be caused, when the transformer is put into a transformer in a man-made normal no-load mode, excitation inrush current of 6-8 times of rated current and overlarge excitation inrush current can be generated due to the fact that the phase angle of system voltage has randomness, the saturation of magnetic flux of an iron core of the transformer and the nonlinear characteristics of the iron core material of the transformer, the misoperation risk of the transformer is increased, and the fault damage probability of normal operation on the transformer is increased.

In order to reduce the damage of the magnetizing inrush current to the transformer, in recent years, researchers have proposed various inrush current suppression methods, including: the method comprises the steps of soft start, positive sequence voltage phase control, SPWM, pre-degaussing, closing resistance, phase selection closing and the like, but part of the methods only stay in a simulation stage, and an excitation inrush current suppression device is mostly adopted on site at present.

At present, a magnetizing inrush current suppression device is mostly adopted on site, and the core of control is to accurately control the opening and closing angle of a circuit breaker so as to realize that residual magnetism and bias magnetism in a magnetic circuit are mutually restricted to reduce magnetizing inrush current. When the protection is switched on again after tripping, the inrush current suppression effect is poor.

Disclosure of Invention

The present invention is directed to a method for suppressing inrush current in an adaptive transformer, so as to solve the problems in the prior art mentioned above.

An adaptive transformer inrush current suppression method comprises the following steps:

s1, acquiring the opening time angle of the transformer breaker;

s2, calculating the relation between the residual magnetic amplitude and the polarity of each phase of the transformer according to the opening angle of each phase;

s3, forming a mathematical model by the residual magnetism of each phase and the three-phase magnetic flux on the power supply side;

s4, seeking the optimal closing angle of the transformer and performing closing operation;

and S5, according to the deviation between the optimal closing angle and the actual closing angle, optimizing the remanence peak coefficient to prepare for the next closing.

Preferably, in S1, the transformer is at t_opnAnd (3) switching off at the moment, wherein the phase of the corresponding A-phase voltage is alpha, and then the three-phase residual magnetism corresponding to the switching off at the moment can be obtained by using a voltage integration method, wherein the three-phase residual magnetism respectively comprises the following components:

wherein phi_Ar、Φ_Br、Φ_CrAre respectively a transformer t_opnA, B, C-phase three-phase remanence at time, K value is single-phase remanence peak coefficient, and phi is taken when first switch is closed_m(iron core magnetic flux amplitude when the transformer operates stably), the value can be optimized gradually through actual phase angle deviation after multiple switchovers in the scheme, and the value is constant before each switchon.

Preferably, the three-phase remanence needs to satisfy the following requirements: phi_Ar+Φ_Br+Φ_Cr＝0。

Preferably, the S3 is a mathematical model of the data obtained in S2 and the expected magnetic flux of the system.

Preferably, it is provided that: the power supply side A phase voltage is U_A(t)＝U_msin (ω t) since the expected flux is 90 ° behind the corresponding phase voltage, there is

Wherein phi_A(t)、Φ_B(t)、Φ_C(t)Are respectively provided withFor three-phase desired flux on the power supply side, phi_mFor the core flux amplitude when the transformer is in stable operation, the dynamic flux of a certain (A) phase of the transformer can be expressed as:

wherein phi_mSaturated magnetic flux,The initial phase angle and the decay time constant of tau of the primary side A phase voltage are obtained, R, L the total resistance and total inductance tau of the single-phase loop of the transformer are equal to L/R, whenDuring the process, the transient magnetic flux in the transformer core can be eliminated and directly enters a steady state (no inrush current is generated), the voltage at the power supply side is a sine wave with the phase angle difference of 120 degrees, and in order to balance the transient magnetic flux of each phase, according to the formula (4), when the expected magnetic flux is closer to the residual magnetism, the transient magnetic flux is smaller, and a demand is neededThe value is such that in the following three formulae Δ Φ_A、ΔΦ_C、ΔΦ_CSimultaneously, the requirements of minimum and three-phase numerical balance are met:

the above-described absolute value mathematical model can be converted into a problem of the expected flux to corresponding phase remanence distance.

Preferably, the graphic analysis method comprises the following steps:

(1) establishing X/Y axis with (0.0) point as center and phi_mDrawing a circle by radius, marking three residual magnetizations phi with the ordinate of three phases on the circle_Ar、Φ_Br、Φ_CrIs assumed to have a value of |. phi_Ar|>|Φ_Br|>|Φ_Cr|；

(2) Since the equation of the circle can be solved, the remanence phi_Ar、Φ_BrThe coordinates on the circle can be found: a1 and B1, connecting the two points, wherein the C1 point of the intersection of the vertical line and the circle is used as the C-phase initial closing angle, and then the A, B-phase initial phase angle can be known;

(3) when C1 goes to phi_CrIs less than or equal to B1 to phi_BrSwitching on according to the initial phase angle; when C1 goes to phi_CrIs greater than B1 to phi_BrIs shifted by the minimum angle theta from the initial phase angle to C1 to phi_CrIs equal to B1 to phi_BrA distance of 1/2 (Y)_C1-Y_B1) And at this time, the angle corresponding to the distance is the final closing angle.

Preferably, when the three-phase remanence is not 0, two optimal closing angles corresponding to the minimum remanence amplitude exist, and the deviation of the two optimal closing angles is not 180 degrees; when the remanence of at least one phase of the three phases is 0, the phase difference of two optimal closing angles corresponding to the remanence of 0 is 180 degrees.

Preferably, when the remanence of a certain phase is 0, the optimal closing angle is an angle corresponding to the remanence of 0, namely k pi, and other phases rotate 120 degrees clockwise and counterclockwise correspondingly on the basis that the remanence of the other phases is 0.

Preferably, in S5, when the closing angle deviates from the actual closing angle, the K value is optimized, and the remanence amplitude is adjusted; when the actual closing angle is ahead of the optimal closing angle, increasing the K value, namely simultaneously increasing the three-phase remanence value; and when the actual closing angle lags behind the optimal closing angle, reducing the K value, enabling the closing angle to be equal to the actual closing angle through adjustment, and recording the residual magnetism calculation coefficient of the K value for residual magnetism evaluation before the next closing.

Preferably, the minimum phase of remanence in remanence of each phase before the transformer is switched on is used as a switching-on reference phase, an optimal switching-on angle is selected according to the corresponding remanence distance of the system, and the next switching-on angle is optimized according to a K value.

The invention has the beneficial effects that: the method comprises the steps of firstly acquiring the relation between the residual magnetism amplitude and the polarity of each phase of the transformer by acquiring the opening moment angle of a breaker of the transformer, then forming a mathematical model by the residual magnetism of each phase and the magnetic flux of each phase of a power supply side to find the optimal closing angle of the transformer, and utilizing a graphic analysis method to find the optimal closing phase rule visually and clearly.

Drawings

The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:

FIG. 1 is a flow chart of a method of the present invention;

fig. 2 is a schematic diagram of capturing a power supply side closing angle.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, 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 application.

Technical terms explain, magnetic flux: in a uniform magnetic field with magnetic induction intensity B, a plane with the area of S and vertical to the direction of the magnetic field is provided, and the product of the magnetic induction intensity B and the area of S is called magnetic flux passing through the plane;

remanence: remanence refers to the residual magnetization of a ferromagnetic material;

expected magnetic flux: a magnetic flux is desired.

The technical solutions provided by the embodiments of the present application are described in detail below with reference to the accompanying drawings.

Referring to fig. 1-2, an adaptive transformer inrush current suppression method includes the following steps:

s1, acquiring the opening time angle of the transformer breaker;

s2, calculating the relation between the residual magnetic amplitude and the polarity of each phase of the transformer according to the opening angle of each phase;

s3, forming a mathematical model by the residual magnetism of each phase and the three-phase magnetic flux on the power supply side;

s4, seeking the optimal closing angle of the transformer and performing closing operation;

and S5, according to the deviation between the optimal closing angle and the actual closing angle, optimizing the remanence peak coefficient to prepare for the next closing.

The method avoids the problem of low residual magnetism precision in the prior stage, selects the optimal closing angle by a method of reducing transient magnetic flux components and utilizing a graphic analysis method to realize the optimal three-phase inrush current suppression effect, and corrects the residual magnetism amplitude according to the closing deviation angle to reduce the deviation between the closing angle and the optimal angle.

The method comprises the steps of calculating remanence of each phase by collecting voltage angles when a transformer breaker is opened, selecting a closing reference phase according to remanence values of each phase, determining an initial three-phase expected magnetic flux angle, comparing an expected magnetic flux of the reference phase with a corresponding phase remanence distance thereof with remanence distances of other phases to the current phase, determining the expected magnetic flux angle as an optimal closing angle when a current is not larger than the initial three-phase expected magnetic flux angle, performing minimum angle offset on the magnetic flux angle when the current is larger than the initial three-phase residual flux angle to obtain the same magnetic flux angle, determining the optimal closing angle when the current is equal to the initial magnetic flux angle, and converting a distance model into an inner angle model if needed.

Preferably, in S1, the transformer is at t_opnAnd (3) switching off at the moment, wherein the phase of the corresponding A-phase voltage is alpha, and then the three-phase residual magnetism corresponding to the switching off at the moment can be obtained by using a voltage integration method, wherein the three-phase residual magnetism respectively comprises the following components:

wherein phi_Ar、Φ_Br、Φ_CrAre respectively a transformer t_opnA, B, C-phase three-phase remanence at time, K value is single-phase remanence peak coefficient, and phi is taken when first switch is closed_mThe value can be gradually optimized through actual phase angle deviation after multiple switchings in the scheme, and the value is all optimized before each switchinginIs a constant.

Preferably, the three-phase remanence needs to satisfy the following requirements: phi_Ar+Φ_Br+Φ_Cr＝0。

Preferably, the S3 is a mathematical model of the data obtained in S2 and the expected magnetic flux of the system.

Preferably, it is provided that: the power supply side A phase voltage is U_A(t)＝U_msin (ω t) since the expected flux is 90 ° behind the corresponding phase voltage, there is

Wherein phi_A(t)、Φ_B(t)、Φ_C(t)Respectively three-phase expected flux of power supply side_mFor the core flux amplitude when the transformer is in stable operation, the dynamic flux of a certain (A) phase of the transformer can be expressed as:

wherein phi_mSaturated magnetic flux,The initial phase angle and the decay time constant of tau of the primary side A phase voltage are obtained, R, L the total resistance and total inductance tau of the single-phase loop of the transformer are equal to L/R, whenDuring the process, the transient magnetic flux in the transformer core can be eliminated and directly enters a steady state (no inrush current is generated), the voltage at the power supply side is a sine wave with the phase angle difference of 120 degrees, and in order to balance the transient magnetic flux of each phase, according to the formula (4), when the expected magnetic flux is closer to the residual magnetism, the transient magnetic flux is smaller, and a demand is neededThe value is such that in the following three formulae Δ Φ_A、ΔΦ_C、ΔΦ_CSimultaneously, the three-phase numerical balance is satisfied as small as possible：

The above-described absolute value mathematical model can be converted into a problem of the expected flux to corresponding phase remanence distance.

Preferably, the graphic analysis method comprises the following steps:

(1) establishing X/Y axis with (0.0) point as center and phi_mDrawing a circle by radius, marking three residual magnetizations phi with the ordinate of three phases on the circle_Ar、Φ_Br、Φ_CrIs assumed to have a value of |. phi_Ar|>|Φ_Br|>|Φ_Cr|；

(2) Since the equation of the circle can be solved, the remanence phi_Ar、Φ_BrThe coordinates on the circle can be found: a1 and B1, connecting the two points, wherein the C1 point of the intersection of the vertical line and the circle is used as the C-phase initial closing angle, and then the A, B-phase initial phase angle can be known;

(3) when C1 goes to phi_CrIs less than or equal to B1 to phi_BrSwitching on according to the initial phase angle; when C1 goes to phi_CrIs greater than B1 to phi_BrIs shifted by the minimum angle theta from the initial phase angle to C1 to phi_CrIs equal to B1 to phi_BrA distance of 1/2 (Y)_C1-Y_B1) And at this time, the angle corresponding to the distance is the final closing angle.

Preferably, when the three-phase remanence is not 0, two optimal closing angles corresponding to the minimum remanence amplitude exist, and the deviation of the two optimal closing angles is not 180 degrees; when the remanence of at least one phase of the three phases is 0, the phase difference of two optimal closing angles corresponding to the remanence of 0 is 180 degrees.

Preferably, when the remanence of a certain phase is 0, the optimal closing angle is an angle corresponding to the remanence of 0, namely k pi, and other phases rotate 120 degrees clockwise and counterclockwise correspondingly on the basis that the remanence of the other phases is 0.

Preferably, in S5, when the closing angle deviates from the actual closing angle, the K value is optimized, and the remanence amplitude is adjusted; when the actual closing angle is ahead of the optimal closing angle, increasing the K value, namely simultaneously increasing the three-phase remanence value; and when the actual closing angle lags behind the optimal closing angle, reducing the K value, enabling the closing angle to be equal to the actual closing angle through adjustment, and recording the residual magnetism calculation coefficient of the K value for residual magnetism evaluation before the next closing.

Preferably, the minimum phase of remanence in remanence of each phase before the transformer is switched on is used as a switching-on reference phase, an optimal switching-on angle is selected according to the corresponding remanence distance of the system, and the next switching-on angle is optimized according to a K value.

In the scheme, the right side of the circle is taken as an example, but in practice, two other intersection points exist between remanence (two phases before amplitude sorting) and the left side of the circle, the method is the same as that of the right side of the circle, and the description is not repeated.

The analysis is performed when the system is laterally symmetrical, but in reality, the system voltage may be slightly asymmetrical due to load imbalance, PT errors or system faults, and the like, so that the analysis is performed under the asymmetrical voltage condition to select a method meeting the actual field requirements: the three-phase asymmetric voltage can be decomposed by a symmetrical component method, positive sequence voltage is obtained, expected magnetic flux corresponding to the positive sequence voltage is obtained by taking the positive sequence voltage as a reference, and the method in the scheme is used for obtaining the optimal closing angle.

According to analysis, the system voltage amplitude is not a key problem of excitation inrush current but a closing phase angle, so that the fact that the three-phase voltage amplitudes at the system side are the same is assumed, the fact that the phase corresponding to the minimum remanence amplitude is the key for determining simultaneous closing of the three phases is determined, and the optimal closing angle can be completed by only taking the phase corresponding to the minimum remanence amplitude as a reference phase and performing the step three (3) and the following steps.

And (3) comprehensive analysis: and taking the minimum remanence phase in the remanence of each phase of the transformer before closing as a closing reference phase. And optimizing the residual magnetism distance (or internal angle) corresponding to each system, selecting an optimal closing angle, and optimizing the K value through the deviation of the closing angle, so as to optimize the residual magnetism after the brake is separated and realize the optimal closing angle.

In summary, the following steps: due to the adoption of the technical scheme, the invention has the following advantages:

1) the method is suitable for the three-phase linkage transformer;

2) the optimal closing angle of each phase can be calculated, the optimal angle of the power supply side three-phase voltage angle and the corresponding phase is captured before closing, and the nearest phase self-adaptive rapid closing can be realized;

3) the problem that one phase or two phases in a fixed phase closing mode are in a high inrush current level for a long time is solved;

4) the breaker can be switched off at any time (angle) without time delay.

5) The remanence is evaluated through a plurality of times of test data, and the calculation precision of the remanence is reduced.

The above description is only an example of the present application and is not intended to limit the present application. Various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application should be included in the scope of the claims of the present application.