CN113777535A

CN113777535A - Current transformer polarity checking method and device, computer equipment and storage medium

Info

Publication number: CN113777535A
Application number: CN202111070502.8A
Authority: CN
Inventors: 习伟; 尹项根; 李肖博; 刘玢岩; 姚浩; 潘远林; 于杨
Original assignee: Southern Power Grid Digital Grid Research Institute Co Ltd
Current assignee: Southern Power Grid Digital Grid Research Institute Co Ltd
Priority date: 2021-09-13
Filing date: 2021-09-13
Publication date: 2021-12-10

Abstract

The application relates to a polarity verification method and device of a current transformer, computer equipment and a storage medium. The protection system applied to the converter transformer comprises the following steps: under the condition that a protection system is switched on in an idle load mode, current information of a current transformer on the network side and current information of a current transformer at a neutral point are obtained; determining the current waveform similarity of the grid-side current transformer and the neutral point current transformer according to the current information of the grid-side current transformer and the current information of the neutral point current transformer; and determining a current phase with abnormal polarity from current phases corresponding to the grid side current transformer and the neutral point current transformer according to the current waveform similarity, and performing polarity verification on the current transformer on the valve side according to the current with abnormal polarity. By adopting the method, the efficiency and the accuracy of the polarity verification of the current transformer can be improved, so that the reliability of the converter transformer protection system is improved.

Description

Current transformer polarity checking method and device, computer equipment and storage medium

Technical Field

The present application relates to the field of power technologies, and in particular, to a method and an apparatus for checking a polarity of a current transformer, a computer device, and a storage medium.

Background

The transformer is an important device in the power transmission and transformation operation of a power system, and a current transformer is commonly used when a protection scheme is configured on the transformer according to a dual protection principle (namely two protection systems are configured). The correctness of the polarity of the current transformer is of great significance to the normal operation of some power equipment in the power system. The wrong polarity of the current transformer can increase the protection failure risk or the protection misoperation risk of the power system, namely, when the system fails, the circuit protection is not carried out or wrong circuit protection instructions are sent out, so that the running reliability of the system is reduced, and therefore the polarity of the current transformer needs to be checked.

The current polarity calibration method of the current transformer is to obtain load current by organizing the load current, manually setting faults, using primary through-flow equipment and the like. Therefore, the correctness of the polarity of the current transformer is judged by adopting a hexagonal graph method based on the load current.

Therefore, the traditional method for verifying the polarity of the current transformer needs to be added with a load, is complex to operate, and has higher operation cost due to the polarity verification of the current transformer. In addition, the conventional current transformer polarity verification method can only determine whether the current transformer has a polarity error by adopting a hexagonal graph method, and when the current transformer has the polarity error, a specific current phase with the polarity error needs to be determined by manual experience. The determination of the wrong polarity phase completely depends on manual experience, and the accuracy of a judgment result cannot be ensured, so that the reliability of the transformer protection system is low.

Disclosure of Invention

The application provides a method and a device for checking the polarity of a current transformer, computer equipment and a storage medium, which can check the polarity of the current transformer in a no-load manner, improve the convenience of checking the polarity of the current transformer, realize the automatic judgment of the wrong polarity of the current transformer and improve the reliability of a transformer protection system.

In a first aspect, a polarity verification method for a current transformer is provided, and is applied to a protection system of a converter transformer, where the protection system includes the converter transformer, a network-side current transformer, a valve-side current transformer, and a neutral-point current transformer, and the method includes: under the condition that a protection system is switched on in an idle load mode, current information of a current transformer on the network side and current information of a current transformer at a neutral point are obtained; determining the current waveform similarity of the grid-side current transformer and the neutral point current transformer according to the current information of the grid-side current transformer and the current information of the neutral point current transformer; and determining a current phase with abnormal polarity from current phases corresponding to the grid side current transformer and the neutral point current transformer according to the current waveform similarity, and performing polarity verification on the current transformer on the valve side according to the current with abnormal polarity.

With reference to the first aspect, in a possible implementation manner of the first aspect, determining current waveform similarities of the grid-side current transformer and the neutral-point current transformer according to current information of the grid-side current transformer and current information of the neutral-point current transformer includes: determining a first current sequence according to current information of the network side current transformer; the first current sequence comprises the sum of three-phase current values of the network side current transformer at different sampling moments; determining a second current sequence according to the current information of the neutral point current transformer; the second current sequence comprises current values of the neutral point current transformer at different sampling moments; and comparing the first current sequence with the second current sequence to obtain the current waveform similarity.

With reference to the first aspect, in a possible implementation manner of the first aspect, comparing current waveforms of the grid-side current transformer and the neutral-point current transformer according to the first current sequence and the second current sequence to obtain a current waveform similarity includes: and calculating the longest common subsequence of the first current sequence and the second current sequence, and determining the similarity of the current waveforms according to the longest common subsequence.

With reference to the first aspect, in a possible implementation manner of the first aspect, determining a current phase with an abnormal polarity from currents corresponding to a grid-side current transformer and a neutral-point current transformer according to a current waveform similarity includes: if the current waveform similarity is smaller than a preset similarity threshold, determining that the current polarities of the network side current transformer and the neutral point current transformer are both abnormal or both normal; if the current waveform similarity is larger than a preset similarity threshold, performing polarity inversion processing on target current phases in the network side current transformer and the neutral point current transformer, and updating the current waveform similarity according to each phase current after the polarity inversion processing; and determining the current phase with abnormal polarity according to the updated current waveform similarity and a preset similarity threshold.

With reference to the first aspect, in a possible implementation manner of the first aspect, performing current phase polarity inversion processing on the grid-side current transformer and the neutral-point current transformer includes: performing current phase polarity inversion processing on one phase or multiple phases in the x-phase current of the grid-side current transformer and the y-phase current of the neutral point current transformer; wherein, the polarities of the other current phases are not changed except for the polarity inversion treatment of the current phase; x and y are integers greater than or equal to 1.

With reference to the first aspect, in a possible implementation manner of the first aspect, determining a current phase with an abnormal polarity according to the updated current waveform similarity and a preset similarity threshold includes: when a converter valve connected with a valve side current transformer is unlocked, acquiring current information and voltage information of a network side current transformer and current information of the valve side current transformer; performing polarity inversion processing on the obtained current of the target current phase, and calculating the active power of the grid-side current transformer according to the current of the target current phase subjected to the polarity inversion processing and the currents of the other current phases of the grid-side current transformer; and determining the current phase with abnormal polarity as a target current phase or the rest phases of the network side current transformer according to the proportion of non-zero power in the active power of the network side current transformer.

With reference to the first aspect, in a possible implementation manner of the first aspect, performing polarity verification on the valve-side current transformer according to the current with the abnormal polarity includes: carrying out polarity inversion processing on the current phase with abnormal polarity to obtain an inverted current value of the current phase with abnormal polarity; performing compensation processing on the inverted current value and the current values of the other current phases of the network side current transformer, and judging whether the current values of all phases after the compensation processing are consistent with the polarity of the corresponding current phase of the valve side current transformer or not; and determining whether the polarity of each current phase of the valve side current transformer is abnormal or not according to the judgment result.

In a second aspect, a current transformer polarity verification apparatus is provided, the apparatus comprising: the acquisition module is used for acquiring current information of a network side current transformer and current information of a neutral point current transformer under the condition that the protection system is switched on in an idle load mode; the determining module is used for determining the current waveform similarity of the grid-side current transformer and the neutral point current transformer according to the current information of the grid-side current transformer and the current information of the neutral point current transformer; and the checking module is used for determining the current phase with abnormal polarity from the current phases corresponding to the grid side current transformer and the neutral point current transformer according to the current waveform similarity, and performing current polarity checking on the valve side current transformer according to the current with abnormal polarity.

In a third aspect, a computer device is provided comprising a memory storing a computer program and a processor. The steps of the method described in the first aspect or any one of the possible implementations of the first aspect above are implemented when a processor executes a computer program.

In a fourth aspect, a computer-readable storage medium is provided, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method according to the first aspect described above or any one of the possible implementations of the first aspect.

The application provides a method and a device for checking polarity of a current transformer, computer equipment and a storage medium, which are applied to a protection system of a converter transformer, wherein the protection system comprises the converter transformer, a network side current transformer, a valve side current transformer and a neutral point current transformer; determining the current waveform similarity of the grid-side current transformer and the neutral point current transformer according to the current information of the grid-side current transformer and the current information of the neutral point current transformer; and determining a current phase with abnormal polarity from current phases corresponding to the grid side current transformer and the neutral point current transformer according to the current waveform similarity, correcting the error polarity of the grid side current transformer, and performing polarity verification on the valve side current transformer according to the corrected polarity of the grid side current transformer.

Therefore, the method provided by the application is used for carrying out polarity verification on the current transformer under the condition of no-load switching-on of the power system (namely, under the condition that the whole power line has no load, an external power supply is supplied to the power line, and the power line is electrified); compared with the prior art that the load current (the current absorbed by the load when the equipment runs) is obtained by organizing the load current, manually setting the fault, using the primary through-flow equipment and the like, and then verifying whether the polarity error exists in the current transformer based on the load current, the method and the device have the advantages that the load is not required to be organized in the power system, the operation is simple, the convenience of polarity verification of the current transformer is improved, and the verification of no load of the current transformer is realized. In addition, the polarity of the current transformer can be verified based on an algorithm, and in the prior art, a hexagonal graph method is adopted manually to judge whether the polarity of the current transformer is wrong, and a specific polarity wrong phase is judged by means of manual experience; compared with the prior art, the method and the device can realize the steps by means of an algorithm, solve the problem that the accuracy of a check result is difficult to guarantee because the prior art depends on manual polarity check of the current transformer, and improve the reliability of a converter transformer protection system.

Drawings

FIG. 1a is a schematic diagram of an electrical system of a method for polarity verification of a current transformer in one embodiment;

FIG. 1b is a schematic diagram of a testing system of a method for checking polarity of a current transformer according to an embodiment;

FIG. 2 is a schematic flow chart diagram illustrating a method for verifying polarity of a current transformer in one embodiment;

FIG. 3 is another schematic flow chart diagram illustrating a method for verifying polarity of a current transformer according to one embodiment;

FIG. 4 is another schematic flow chart diagram illustrating a method for verifying polarity of a current transformer according to one embodiment;

FIG. 5 is another schematic flow chart diagram illustrating a method for verifying polarity of a current transformer in accordance with one embodiment;

FIG. 6 is another schematic flow chart diagram illustrating a method for verifying polarity of a current transformer in accordance with one embodiment;

FIG. 7 is a diagram illustrating a polarity verification result of the current transformer in one embodiment;

FIG. 8 is a power waveform diagram of a current transformer in one embodiment;

FIG. 9 is a block diagram showing the structure of a polarity verifying unit of a current transformer in one embodiment;

FIG. 10 is a diagram showing an internal structure of a computer device according to an embodiment.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

The polarity verification method for the current transformer can be applied to the power system shown in fig. 1. Referring to fig. 1a, the power system includes a grid-side current transformer 10, a neutral point current transformer 20, a valve-side current transformer 30, a voltage transformer 40, and a converter transformer 50. The network-side current transformer 10 is located on the network side of the converter transformer 50 (the side of the converter transformer connected to the ac power grid), and can measure current information on the network side of the converter transformer; the valve-side current transformer 30 is located on the valve side of the converter transformer 50 (the side where the converter transformer is connected to the converter valve), and can measure the current information on the valve side of the converter transformer; the neutral point current transformer 20 is positioned in a grounded line of the converter transformer 50, and can measure current information of the neutral point of the converter transformer; the voltage transformer 40 is located on the network side of the converter transformer 50, and can measure the voltage information on the network side of the converter transformer.

In the embodiment of the present application, the power system shown in fig. 1 may also be referred to as a protection system of a converter transformer.

Fig. 1b is a schematic diagram of a test system provided in an embodiment of the present application, and referring to fig. 1a, the system includes a test device 60 and a power system. The power system may be the power system shown in fig. 1, or may be a protection system of a converter transformer; the test equipment can be a mobile phone, a computer or other computer equipment.

In the embodiment of the application, the testing device can send a testing instruction to the power system, trigger the power system to perform polarity testing of the current transformer, and can perform processes such as calculation and judgment according to collected testing data, so as to check the polarity of the current transformer.

At present, the polarity verification of the current transformer is mainly to obtain the load current by organizing the load current, artificially setting faults, using a primary through-flow device and other methods, artificially verifying whether the current transformer has a polarity error by using a hexagonal graph method based on the load current, and judging a specific polarity error phase by depending on artificial experience. This kind of mode needs to rely on the manual work to carry out the polarity check to current transformer based on load current under the circumstances that power system has the load for the check-up result accuracy is poor, and the check-up process automation degree is low, and is loaded down with trivial details and inefficiency. Therefore, the problems of poor accuracy and low efficiency of polarity verification of the current transformer exist at present.

Based on this, the embodiment of the application provides a method for checking the polarity of a current transformer, which can realize the no-load and automatic polarity checking of the current transformer and improve the checking efficiency and accuracy. Fig. 2 is a schematic flowchart of a polarity verification method for a current transformer according to an embodiment of the present disclosure, and the method is applied to the system shown in fig. 1, and an execution subject of the method may be the testing apparatus 60 in the system shown in fig. 1 b. As shown in fig. 2, the method comprises the steps of:

step 201, acquiring current information of a network side current transformer and current information of a neutral point current transformer under the condition of no-load switching-on of a protection system of a converter transformer;

in order to realize the polarity verification of the unloaded current transformer in the embodiment of the application, it needs to be ensured that the current information for verifying the polarity of the current transformer is acquired under the condition that the protection system is unloaded. Therefore, the current information of the grid-side current transformer and the current information of the neutral point current transformer are acquired under the condition that the protection system is switched on in an idle state.

In a possible implementation manner, the switch is controlled to be switched on manually under the condition of an external power supply, so that the protection system is electrified. At the moment, the three-phase current i at the moment of electrifying the protection system is measured by the grid-measuring current transformer_{ACY_A}、i_{ACY_B}、i_{ACY_C}And the current i measured by the neutral point current transformer_GND。

In a possible implementation manner, the testing device 60 may instruct the power system to enter an idle-load closing state, so as to implement automatic control of closing of the switch. Specifically, after receiving the instruction for starting polarity verification, the testing device sends a closing instruction to a switch between the converter transformer and the ac power grid, instructs the switch to perform closing operation, and obtains the three-phase current of the current transformer and the current of the neutral point current transformer measured by the grid at the moment of closing. The testing device can indicate the switch to be switched on in a wired or wireless mode.

It should be noted that the no-load closing finger connects the network side of the converter transformer to the rated voltage under the condition that no load is carried on the valve side of the converter transformer. The converter transformer valve side may also be referred to as the secondary side, and the converter transformer grid side may also be referred to as the primary side.

Step 202, determining the current waveform similarity of the grid side current transformer and the neutral point current transformer according to the current information of the grid side current transformer and the current information of the neutral point current transformer;

in the embodiment of the application, in order to judge whether the three-phase polarity of the grid-side current transformer is correct, the polarity of the neutral point current transformer can be introduced for auxiliary judgment. Because the converter transformer and the converter valve form a converter, the mutual conversion of alternating current and direct current is realized. The converter transformer is mainly used for converting an alternating current system voltage into a commutation voltage required by a converter, and does not relate to current conversion, namely, the currents flowing through a network side, a neutral point and a valve side of the converter transformer are the same. Therefore, the polarity of the neutral point current transformer can be introduced to perform auxiliary judgment on the polarity of the grid side current transformer.

In a possible implementation manner, whether the currents flowing through the network side and the neutral point of the converter transformer are consistent or not can be judged by using the current waveform similarity of the network side current transformer and the neutral point current transformer, so as to judge whether the polarity error exists in the network side current transformer or not. The current waveform similarity can represent the similarity between the current of the grid-side current transformer and the current of the neutral-point current transformer.

And 203, determining a current phase with abnormal polarity from current phases corresponding to the grid side current transformer and the neutral point current transformer according to the current waveform similarity, and performing polarity verification on the current transformer on the valve side according to the current with abnormal polarity.

In the embodiment of the application, when the polarity of the current transformer is comprehensively checked, the three-phase polarity of the current transformer on the network side can be checked, and further, the polarity of the current transformer on the valve side can be checked according to the polarity checking result of the current transformer on the network side. For example, it may be determined whether a polarity error exists in the grid-side current transformer, and when the polarity error exists in the grid-side current transformer, a specific polarity abnormal current phase is determined. And polarity verification can be carried out on the current transformer at the valve side according to the current with abnormal polarity.

In a possible implementation manner, a current phase with abnormal polarity can be determined from current phases corresponding to a network side current transformer and a neutral point current transformer by utilizing waveform similarity; when the waveform similarity is high, the polarities of the grid-side current transformer and the neutral point current transformer are all correct or all wrong; when the waveform similarity is low, the grid-side current transformer and the neutral point current transformer have the condition of polarity error.

In a possible implementation manner, based on the consistency of the current of the converter transformer on the network side and the current of the converter transformer on the valve side, whether a polarity error or a specific polarity error phase exists in the current transformer on the valve side can be judged by using the polarity condition of the current transformer on the network side. The polarity of the current transformer at the valve side is judged by utilizing the polarity of the current transformer at the network side, and the judgment can be carried out only when the network side and the valve side are in a closed circuit.

According to the polarity verification method for the current transformer, the polarity of the current transformer can be verified under the condition that the power system is switched on in an idle load mode; the problems that in the prior art, the load current is obtained by organizing the load current, manually setting faults, using primary through-flow equipment and the like, the verification process is complex and the efficiency is low are solved, and the verification of no load of the current transformer is realized. In addition, the polarity of the current transformer can be checked based on the algorithm, the problem that in the prior art, a hexagonal diagram is drawn manually to judge whether the polarity of the current transformer is wrong or not, and the specific polarity error phase is judged by means of human experience, so that the accuracy of a checking result is difficult to guarantee is solved, the whole checking process is simple to operate, the consumed time is short, the accuracy of the checking result is high, and the reliability of a converter transformer protection system is improved.

In the embodiment of the application, the waveform comparison can be performed on the network side and the neutral point current of the converter transformer based on the current sequence, so that the current waveform similarity of the network side and the neutral point current of the converter transformer can be obtained. For example, the specific implementation of "determining the current waveform similarity of the grid-side current transformer and the neutral-point current transformer according to the current information of the grid-side current transformer and the current information of the neutral-point current transformer" in the foregoing step 202 includes the steps shown in fig. 3:

step 301, determining a first current sequence according to current information of a network side current transformer; the first current sequence comprises the sum of three-phase current values of the network side current transformer at different sampling moments;

in order to obtain the current waveform similarity of the grid-side current transformer and the neutral point current transformer, the current waveform of the grid-side current transformer needs to be known.

In a possible implementation manner, the current of the grid-side current transformer may be sampled at equal intervals to obtain three current values of the current of each phase of the grid-side current transformer at different sampling moments, and the sum of the three-phase current values at the sampling moment is determined according to the three current values. And obtaining a first current sequence according to the sum of the three-phase current values at different sampling moments, wherein the first current sequence is used for representing the current waveform of the network side current transformer. Wherein, the current of the network side current transformer is three-phase current i of the network side current transformer_{ACY_A}、i_{ACY_B}、i_{ACY_C}The sum of (1).

Step 302, determining a second current sequence according to current information of the neutral point current transformer; the second current sequence comprises current values of the neutral point current transformer at different sampling moments;

in order to obtain the current waveform similarity of the grid-side current transformer and the neutral point current transformer, the current waveform of the grid-side current transformer and the current waveform of the neutral point current transformer need to be known.

In a possible implementation manner, the current of the neutral point current transformer can be sampled at equal intervals, and current values of the current of the neutral point current transformer at different sampling moments are obtained. And obtaining a second current sequence according to the current values at different sampling moments, wherein the second current sequence is used for representing the current waveform of the neutral point current transformer. Wherein, the current of the neutral point current transformer is the current i measured by the neutral point current transformer_GND。

It should be noted that the sampling time instants of the first current sequence and the second current sequence are aligned. For example, the three-phase current of the grid-side current transformer is sampled at the time T1, and the current x1 of the grid-side current transformer at the time T1 is obtained; one phase current of the neutral point current transformer is sampled at the time T1, and the current y1 of the neutral point current transformer at the time T1 is obtained. Sampling three-phase current of the grid-side current transformer at the time of T2 to obtain current x2 of the grid-side current transformer at the time of T2; one phase current of the neutral point current transformer is sampled at the time T2, and the current y2 of the neutral point current transformer at the time T2 is obtained. Sampling three-phase current of the grid-side current transformer at the time of T3 to obtain current x3 of the grid-side current transformer at the time of T3; one phase current of the neutral point current transformer is sampled at the time T3, and the current y3 of the neutral point current transformer at the time T3 is obtained. Sampling three-phase current of the grid-side current transformer at the time of T4 to obtain current x4 of the grid-side current transformer at the time of T4; one phase current of the neutral point current transformer is sampled at the time T4, and the current y4 of the neutral point current transformer at the time T4 is obtained. Sampling three-phase current of the grid-side current transformer at the time of T5 to obtain current x5 of the grid-side current transformer at the time of T5; one phase current of the neutral point current transformer is sampled at the time T5, and the current y5 of the neutral point current transformer at the time T5 is obtained.

Based on this, a first current sequence [ x1, x2, x3, x4, x5] is obtained, a second current sequence [ y1, y2, y3, y4, x5 ].

And 303, comparing current waveforms of the network side current transformer and the neutral point current transformer according to the first current sequence and the second current sequence to obtain current waveform similarity.

In a possible implementation manner, current waveform comparison may be performed on the first current sequence and the second current sequence, and the waveform comparison result may represent the current waveform similarity between the grid-side current transformer and the neutral-point current transformer. Specifically, the similarity of the currents in the first current sequence and the second current sequence can be compared by using an algorithm, and a comparison result is output as a basis for judging the similarity of the current waveforms of the grid-side current transformer and the neutral-point current transformer.

The embodiment of the application provides a method for determining the current waveform similarity of a grid-side current transformer and a neutral point current transformer according to the current information of the grid-side current transformer and the current information of the neutral point current transformer. Specifically, current values of the grid-side current transformer and the neutral point current transformer at different sampling moments are obtained and used as current sequences of the grid-side current transformer and the neutral point current transformer, algorithm-based comparison is carried out on the two current sequences, and the obtained comparison result can represent the current waveform similarity of the grid-side current transformer and the neutral point current transformer. The current sequences of the grid-side current transformer and the neutral point current transformer are compared to obtain the current waveform similarity of the grid-side current transformer and the neutral point current transformer. The current sequence obtained by sampling has small sampling interval and large sampling density, and can accurately represent the characteristics of current waveforms, so that the current sequences of the network side current transformer and the neutral point current transformer are compared, and more accurate waveform similarity can be obtained. And only the current values obtained by sampling are compared, so that the calculation amount of the whole waveform similarity calculation process is greatly reduced.

In the embodiment of the present application, the similarity between the first current sequence and the second current sequence may be determined by using a longest common subsequence algorithm. For example, the foregoing step 303 "comparing current waveforms of the grid-side current transformer and the neutral-point current transformer according to the first current sequence and the second current sequence to obtain the current waveform similarity", specifically implemented as follows:

and calculating the longest common subsequence of the first current sequence and the second current sequence, and determining the similarity of the current waveforms according to the longest common subsequence.

The longest common subsequence refers to a subsequence that is the longest among all sequences in a set of sequences (typically two sequences). In addition, the subsequence need only maintain the relative order of the elements consistent and does not require the elements to be contiguous, e.g., a subsequence of { a, b, c, d, e, f, g, h } can be { a, b, c, d } or { a, h } or { b, d, f }.

One possible implementation manner may be to calculate the longest common subsequence LCS of the first current sequence and the second current sequence based on an algorithm, normalize the longest common subsequence LCS to obtain the longest common subsequence distance L, and determine the current waveform similarity of the network-side current transformer and the neutral-point current transformer according to a waveform similarity criterion (i.e., the smaller the value of L, the higher the waveform similarity).

Wherein, the calculation formula of the longest common subsequence LCS is shown as formula (1):

equation (1) shows that when the characters of the corresponding positions of the arrays a and b are the same, the next position is directly solved, and the larger value in the two cases is not taken simultaneously.

Wherein a [ i ] is the ith element in the array a; b [ j ] is the jth element in array b. Epsilon is a similarity threshold value of the sequence point pair, if the difference value of the point pair (i.e. a [ i ] -bj ]) is considered to be the same between two points in the range, so as to increase the waveform similarity, the embodiment considers the propagation error of the current transformer (the error of the current measured by the current transformer) to be 10%, therefore, the similarity threshold value of the point pair in an ideal state is ignored to be 0, the similarity threshold value of the point pair is set to be 10%, and the similarity threshold value of the point pair can be adaptively adjusted.

Wherein, the calculation formula of the longest common subsequence distance L is shown as formula (2):

L＝1-LCS(i,j)/min(m,n) (2)

the expression (2) indicates the normalization to the LCS.

Wherein m is the length of the array a, and n is the length of the array b.

The embodiment of the application provides a method for determining the similarity of current waveforms of a network side current transformer and a neutral point current transformer through current sequences of the network side current transformer and the neutral point current transformer. Specifically, the longest common subsequence LCS of the first current sequence and the second current sequence is calculated by an algorithm, the longest common subsequence LCS is normalized to obtain the longest common subsequence distance L, and the current waveform similarity of the network side current transformer and the neutral point current transformer is determined by a waveform similarity criterion. When the current waveform similarity of the network side current transformer and the neutral point current transformer is obtained, the longest common subsequence LCS is introduced, and the polarity verification adaptability of the embodiment of the application to various adverse working conditions (errors of current measured by the current transformers, noise influence of a system and the like) is improved by setting a non-zero point pair similarity threshold. And normalizing the obtained longest common subsequence LCS to obtain the longest common subsequence distance L, and more intuitively measuring the similarity of the current waveform of the network side current transformer and the neutral point current transformer by using a specific numerical value.

In the embodiment of the application, the current waveform similarity of the grid-side current transformer and the neutral point current transformer can be compared with a preset similarity threshold, so that the corresponding current phase with abnormal polarity can be determined. For example, the "determining a current phase with abnormal polarity from currents corresponding to the grid-side current transformer and the neutral-point current transformer according to the similarity of the current waveforms" in the foregoing step 203 specifically includes the steps shown in fig. 4:

step 401, if the current waveform similarity is smaller than a preset similarity threshold, determining that the current polarities of the network side current transformer and the neutral point current transformer are both abnormal or both normal;

in order to determine the polarity conditions of the grid-side current transformer and the neutral point current transformer conveniently according to the current waveform similarity, a specific numerical value of the longest common subsequence distance L capable of representing the current waveform similarity is compared with a preset similarity threshold, and the polarity conditions of the grid-side current transformer and the neutral point current transformer are determined according to a comparison result.

In the specific implementation, if the current waveform similarity is smaller than a preset similarity threshold (that is, the longest common subsequence L is smaller than the preset similarity threshold), it indicates that the current waveform similarities of the network-side current transformer and the neutral-point current transformer are high, that is, the current waveforms of the network-side current transformer and the neutral-point current transformer are relatively consistent. Therefore, the current polarities of the grid-side current transformer and the neutral point current transformer are both abnormal or normal.

In a possible implementation manner, considering influences of transmission errors, noise interference and the like of a current transformer configured in an actual power grid, in order to resist the interference errors and obtain higher verification sensitivity, a similarity threshold value may be 0.015, and the longest common subsequence distance L (ideally, the threshold value is 0) is compared with 0.015. Wherein 0.015 is a conclusion obtained after the present application is demonstrated in many ways (including performing simulation experiments on the present solution, etc.), and may also be other methods, which is not limited in the present application according to specific situations.

Step 402, if the current waveform similarity is greater than a preset similarity threshold, performing polarity inversion processing on target current phases in the network side current transformer and the neutral point current transformer, and updating the current waveform similarity according to each phase current after the polarity inversion processing;

in the specific implementation, if the current waveform similarity is greater than a preset similarity threshold (that is, the longest common subsequence L is greater than the preset similarity threshold), it indicates that the current waveform similarities of the network-side current transformer and the neutral-point current transformer are low, that is, there are current phases with wrong polarities in the network-side current transformer and the neutral-point current transformer.

In a possible implementation manner, polarity inversion processing is performed on a target current phase in a network side current transformer and a neutral point current transformer (namely, the current direction of the target current phase is inverted), and the sum of three-phase current values is recalculated according to the three-phase current of the network side current transformer after the polarity inversion processing of the target current phase to be used as the current of the network side current transformer; and the current of the neutral point current transformer after the target current phase polarity inversion processing is the current of the neutral point current transformer. And calculating the longest common subsequence of the current of the network side current transformer and the current of the neutral point current transformer, further calculating the distance of the longest common subsequence, and obtaining the current waveform similarity after the inversion processing of the phase polarity of the target current so as to update the current waveform similarity of the network side current transformer and the neutral point current transformer. The target current phase is a current phase with a wrong polarity in the network side current transformer and the neutral point current transformer.

In a possible implementation manner, if the current waveform similarity is equal to the preset similarity threshold, the polarity conditions of the grid-side current transformer and the neutral-point current transformer may be classified as the conditions that the polarities are both abnormal or normal, or may be classified as the conditions that the grid-side current transformer and the neutral-point current transformer have current phases with wrong polarities, which is not limited in this application.

When the polarities of the grid-side current transformer and the neutral-point current transformer are both normal or both abnormal, the process of inverting the polarity of the target current phase still needs to be performed, and the current waveform similarity needs to be updated according to each phase current after the polarity inversion.

And step 403, determining the current phase with abnormal polarity according to the updated current waveform similarity and a preset similarity threshold.

In the specific implementation, the updated current waveform similarity is compared with a preset similarity threshold, and according to the comparison result, the target current phase corresponding to the current waveform similarity smaller than the preset similarity threshold is determined, namely the current phase with abnormal polarity.

The embodiment of the application provides a method for determining a current phase with abnormal polarity according to current waveform similarity, which specifically comprises the steps of comparing the current waveform similarity with a preset similarity threshold, and if the current waveform similarity is smaller than the preset similarity threshold, judging whether the current polarities of a network side current transformer and a neutral point current transformer are both abnormal or normal; and otherwise, the current transformer at the network side and the current transformer at the neutral point have current phases with wrong polarities. And calculating the current waveform similarity of the current of the grid side current transformer and the current of the neutral point current transformer through the current of the grid side current transformer and the current of the neutral point current transformer which are obtained through calculation after the polarity inversion processing, and finishing the updating of the current waveform similarity. And comparing the updated current waveform similarity with a preset similarity threshold, and determining a target current phase corresponding to the current waveform similarity smaller than the preset similarity threshold according to a comparison result, namely the current phase with abnormal polarity. Therefore, the current phase with abnormal polarity can be determined by correcting the target current phase, updating the current waveform similarity and using the updated current waveform similarity and a preset similarity threshold. The steps can be completed based on an algorithm, the problem that the accuracy of a check result is difficult to guarantee due to the fact that the specific polarity error phase is judged by means of human experience in the prior art is solved, and the reliability of the converter transformer protection system is improved.

When determining the phase with the abnormal polarity, the polarity inversion processing may be performed on the target current phase in the network side current transformer and the neutral point current transformer. For example, the foregoing "performing polarity inversion processing on the target current phase in the grid-side current transformer and the neutral-point current transformer" in step 402 is specifically implemented as follows:

performing current phase polarity inversion processing on one phase or multiple phases in the x-phase current of the grid-side current transformer and the y-phase current of the neutral point current transformer; wherein, the polarities of the other current phases are not changed except for the polarity inversion treatment of the current phase; x and y are integers greater than or equal to 1.

In order to determine the current phase with abnormal polarity, one or more phases of the x-phase current of the grid-side current transformer and the y-phase current of the neutral-point current transformer may be subjected to polarity inversion processing, the polarities of the other current phases are unchanged, the current waveform similarity between the grid-side current transformer and the neutral-point current transformer after the polarity inversion processing is calculated, and the current waveform similarity is compared with a preset similarity threshold. If the current waveform is smaller than the preset similarity threshold, it is indicated that the current waveform similarity of the grid-side current transformer and the neutral point current transformer after the polarity inversion processing is high, that is, the current waveforms of the grid-side current transformer and the neutral point current transformer after the polarity inversion processing are relatively consistent, so that the current phase subjected to the polarity inversion processing is the current phase with abnormal polarity. Wherein x and y are integers greater than or equal to 1.

In a specific implementation, x may be 3, y may be 1, and if there are polarity errors in three phases A, B, C of the grid-side current transformer and in current phase N of the neutral-point current transformer, there are 16 error cases, which may be divided into 8 polarity error cases, where each polarity error case is divided into two types, that is, I-type polarity error cases: A. b, C, AB, AC, BC, ABC, ABCN and class II polarity error cases: BCN, ACN, ABN, CN, BN, AN, N, all correct. Wherein, the I type error condition and the II type error condition in the 8 polarity error conditions are in one-to-one correspondence. And the judgment of the waveform similarity can only judge that the polarity error condition is one of 8 types, and can not judge which type of the polarity error condition is specific. For example, if the target current phase is BC, the BC current phase is inverted, the current waveform similarity of the inverted network side current transformer and the neutral point current transformer is recalculated, and when the current similarity is smaller than a preset similarity threshold, it indicates that the phase with the wrong polarity is BC phase or AN phase corresponding to BC.

In one possible implementation, the I-type polarity error condition is traversed, that is, the current of the target current phase in the I-type polarity error condition is inverted, the longest common subsequence distance L between the inverted current of the grid-side current transformer and the current of the neutral-point current transformer is calculated, and the distance set Q ═ { L ═ is obtained_A,L_B,L_C,L_AB,L_AC,L_BC,L_ABC,L_ABCD}. And judging an L value smaller than 0.015 in the distance set Q, wherein a polarity error condition (target current phase polarity error) corresponding to the L value and a class II polarity error condition (other phase polarity errors except the target current phase) corresponding to the polarity error condition are two possible polarity error conditions. For example, if L_BCIf the value is less than 0.015, BC and the class II polarity error condition AN corresponding to BC are two possible polarity error conditions.

In a possible implementation manner, the I-type polarity error condition may be sequentially traversed, because there is one and only one L value of the I-type polarity error condition is less than 0.015, when the L value less than 0.015 is sequentially calculated, the corresponding polarity error and the II-type polarity error condition corresponding to the polarity error condition are two possible polarity error conditions, and it is not necessary to calculate the subsequent polarity error condition that is not traversed.

The embodiment of the application provides a method for determining a current phase with abnormal polarity by performing polarity inversion processing on the current phase, and specifically, the method includes traversing I-type polarity error conditions in 16 polarity error conditions, respectively inverting corresponding error phase currents of the I-type polarity error conditions, and then calculating the longest common subsequence distance L between the current of a network side current transformer and the current of a neutral point current transformer to obtain the longest common subsequence distance L between the current of the network side current transformer and the current of the neutral point current transformerSet Q ═ L_A,L_B,L_C,L_AB,L_AC,L_BC,L_ABC,L_ABCD}. And judging the L value smaller than 0.015 in the distance set Q, wherein the polarity error condition corresponding to the L value and the class II polarity error condition corresponding to the polarity error condition are two possible polarity error conditions. The method and the device can determine the polarity abnormal conditions of the two possible network side current transformers and the neutral point current transformer by utilizing the polarity inversion operation of the target current phase based on the algorithm. Based on the result, subsequent determination of a specific polarity abnormal phase can be made, and a unique polarity error condition can be determined from two possible polarity error conditions.

In the embodiment of the application, the specific current phase with abnormal polarity can be determined according to the comparison result of the updated current waveform similarity and the preset similarity threshold. For example, the specific implementation of "determining a current phase with abnormal polarity according to the updated current waveform similarity and the preset similarity threshold" in step 403 includes the steps shown in fig. 5:

step 501, when a converter valve connected with a valve side current transformer is unlocked, acquiring current information and voltage information of a network side current transformer and current information of the valve side current transformer;

when the converter valve is unlocked, the charging process of the sub-modules (part of the small modules forming the converter valve) in the converter valve can be equivalent to the charging process of the RC circuit, so that when the converter valve is unlocked, the instantaneous power of the power system is active power, namely the instantaneous power p is always greater than 0. In order to determine the specific polarity error phase of the current transformer by using the instantaneous active power of the grid-side current transformer, it is necessary to obtain current information and voltage information of the grid-side current transformer and current information of the valve-side current transformer at the moment of unlocking the converter valve so as to calculate the instantaneous active power of the grid-side current transformer.

In a possible implementation manner, when the protection system is switched on in an idle state, the external power supply charges the whole protection system, and the converter valve is connected with a converter transformer in the protection system through a valve side current transformer, so that the external power supply is externally connected with the converter transformer in the protection systemThe power supply charges the converter valve at the same time until the converter valve reaches a threshold value and is unlocked, and a three-phase current value i of the current transformer on the network side at the moment of unlocking the converter valve is obtained_a、i_bAnd i_cThree-phase voltage value u of converter transformer_a、u_bAnd u_cAnd three-phase current value i of valve-side current transformer_{VY_A}、i_{VY_B}And i_{VY_C}。

Wherein, because the power line has no load, the calculated instantaneous active power of the grid-side current transformer can represent the instantaneous active power of the whole power line.

502, performing polarity inversion processing on the obtained current of the target current phase, and calculating the active power of the grid-side current transformer according to the current of the target current phase subjected to the polarity inversion processing and the currents of the other current phases of the grid-side current transformer;

to calculate the active power of the grid-side current transformer, the correct current of the grid-side current transformer is obtained first, and therefore, the polarity of the target current phase is inverted for the type I polarity error condition in the polarity error condition obtained above.

In specific implementation, according to the current after polarity inversion processing of the target current phase, the currents of the other current phases of the network side current transformer and the voltages of the phases of the voltage transformer, the active power of the network side current transformer is calculated by using the formula (3):

p＝u_ai_a+u_bi_b+u_ci_c (3)

in a possible implementation mode, because the traditional power theory cannot well reflect the changes of voltage and current of a non-sinusoidal signal in a transient process, the voltage and the current are converted into an alpha-beta coordinate through Clark conversion (namely, three-phase alternating current of the current is converted into two direct current), and then inverse conversion is carried out. And substituting the voltage and current values subjected to Clark transformation and inverse transformation into the formula (3) for calculation to obtain the active power of the network side current transformer.

Step 503, determining the current phase with abnormal polarity as the target current phase or the rest phases of the grid-side current transformer according to the proportion of the nonzero power in the active power of the grid-side current transformer.

When the polarity of the current transformer on the network side is correct, the instantaneous power of the power system at the moment of unlocking the converter valve is active power, namely the instantaneous power p is always greater than 0. Due to the three-phase power symmetry of the current transformer, the three-phase amplitudes of the current transformer are also similar, if the grid-side current transformer is connected with a reversed phase (namely a phase with a wrong polarity), the instantaneous active power of the grid-side current transformer obviously crosses a zero point and begins to oscillate, namely the moment of the instantaneous active power p is greater than 0. Therefore, the current phase with abnormal polarity can be determined to be the target current phase or the rest phases of the network side current transformer according to the proportion of non-zero power in the active power of the network side current transformer at the moment of unlocking the converter valve.

In a possible implementation manner, the proportion of non-zero power in the active power of the grid-side current transformer is calculated by using an algorithm, and if the proportion is greater than 98.5%, it is indicated that the three-phase polarity of the grid-side current transformer after polarity inversion processing is performed on a target current phase in the case of I-type polarity error is correct, namely the polarity error case of the grid-side current transformer is the case of I-type polarity error; and if the specific gravity is less than 98.5%, the polarity error condition of the network side current transformer is a type II polarity error condition.

The embodiment of the application provides a method for determining the only polarity error condition from two types of polarity error conditions, and specifically, the method comprises the steps of firstly obtaining a three-phase current value i of a network side current transformer at the moment of unlocking a converter valve_a、i_bAnd i_cThree-phase voltage value u of converter transformer_a、u_bAnd u_cAnd three-phase current value i of valve-side current transformer_{VY_A}、i_{VY_B}And i_{VY_C}. And then, carrying out polarity inversion processing on the target current phase under the I-type polarity error condition, and calculating the active power of the grid-side current transformer according to the current subjected to polarity inversion processing, the currents of the other current phases of the grid-side current transformer and the voltages of all phases of the voltage transformer. And finally, calculating the proportion of non-zero power in the active power of the network side current transformer by using an algorithm, wherein if the proportion is more than 98.5 percent, the network side current mutual current is indicatedThe polarity error condition of the sensor is a type I polarity error condition, and conversely, the polarity error condition is a type II polarity error condition. Therefore, the method and the device for detecting the polarity of the current transformer can detect whether the current transformer has the polarity error or not, can detect the specific polarity error phase of the current transformer, and can detect whether the current transformer has the polarity error or not only compared with the prior art, and the method and the device for detecting the polarity of the current transformer are more comprehensive. Compared with the prior art that the specific polarity error phase is judged by means of human experience, the polarity verification of the current transformer based on the algorithm has the advantages of higher efficiency and higher accuracy, so that the reliability of the converter transformer protection system is higher.

In the embodiment of the application, the polarity of each phase of the valve side current transformer can be verified according to the polarity of each phase of the network side current transformer after the error polarity inversion processing. For example, the "performing polarity check on the valve-side current transformer according to the current with abnormal polarity" in the foregoing step 203 specifically includes the steps shown in fig. 6:

601, performing polarity inversion processing on the current phase with the abnormal polarity to obtain an inverted current value of the current phase with the abnormal polarity;

in order to obtain the polarity condition of the valve side current transformer, the polarity of the grid side current transformer can be used for carrying out polarity verification on the valve side current transformer, and firstly, the correct polarity of the grid side current transformer needs to be obtained.

In a possible implementation manner, polarity inversion processing is performed on the checked error polarity of the grid-side current transformer, so as to obtain an inverted current value of the error polarity.

Step 602, performing compensation processing on the inverted current value and current values of the other current phases of the network side current transformer, and judging whether the current values of the phases after the compensation processing are consistent with the polarities of the corresponding current phases of the valve side current transformer;

because of the wiring manner of the converter transformer, when the current flows from the network side to the valve side, the current has some phase and amplitude changes, so the network side is usedThe polarity of the current transformer is used for checking the polarity of the valve side current transformer, and the three-phase compensation current i of the network side current transformer needs to be calculated firstly_A、i_BAnd i_CAnd eliminating the error between the current of the grid-side current transformer and the current of the valve-side current transformer.

In specific implementation, the network side current can be inverted and corrected according to the inverse current of the butt joint of the verification result, and then the compensation current of the network side current transformer is calculated by using the formula (4):

and judging whether the compensation current of each phase of the grid-side current transformer is consistent with the polarity of the corresponding current phase of the valve-side current transformer (namely the A phase of the grid-side current transformer and the A phase of the valve-side current transformer).

In a possible implementation manner, the waveform similarity of the compensation current of each phase of the grid-side current transformer and the current of the corresponding current phase of the valve-side current transformer can be calculated through traversal, and compared with a preset waveform similarity threshold value, so as to judge whether the polarity of each phase of the valve-side current transformer is correct or not.

The compensation current of the valve side current transformer can be calculated, and the error between the current of the grid side current transformer and the current of the valve side current transformer can be eliminated as long as the error is guaranteed, so that the method is not limited by the application.

Step 603, determining whether the polarity of each current phase of the valve side current transformer is abnormal according to the judgment result.

And determining whether the polarity of each current phase of the valve side current transformer is abnormal or not according to the comparison result, specifically calculating the longest common subsequence distance L between the compensation current of each phase of the grid side current transformer and the current of the corresponding current phase of the valve side current transformer, and judging whether L is smaller than 0.015 or not, if so, the polarity of the phase of the valve side current transformer is correct, otherwise, the polarity of the phase is wrong.

The embodiment of the application provides a method for checking the polarity of a valve side current transformer according to the polarity of a network side current transformer, and specifically, polarity inversion processing is performed on the wrong polarity of the network side current transformer, the compensation current of the network side current transformer is calculated by using the current of the network side current transformer after the polarity inversion processing, the longest public subsequence distance L between the compensation current of each phase of the network side current transformer and the current of the corresponding current phase of the valve side current transformer is calculated, whether L is smaller than 0.015 or not is judged, if yes, the phase polarity of the valve side current transformer is correct, and if not, the phase polarity is wrong. Therefore, the polarity of the valve side current transformer can be verified through the polarity of the network side current transformer, the process of verifying the polarity of the valve side current transformer is greatly reduced, and the verification efficiency is improved. According to the embodiment of the application, the polarity of the valve side current transformer is verified by utilizing the compensated polarity of the network side current transformer, so that the accuracy of the polarity verification of the valve side current transformer is improved.

Taking polarity verification of a network side current transformer and a valve side current transformer of a converter transformer as an example, the method for verifying the polarity of the current transformer provided by the application is explained in detail, and specifically comprises the following steps:

s1, obtaining three-phase current i of network side current transformer at no-load switching-on moment of converter transformer protection system_{ACY_A}、i_{ACY_B}、i_{ACY_C}. Current i to neutral point current transformer_GND. The current of the network side current transformer is three-phase current and i₀。

S2, i₀And i_GNDSampling is carried out, and a corresponding first current sequence and a corresponding second current sequence are obtained. Calculating the longest common subsequence LCS of the first current sequence and the second current sequence, and calculating the longest common subsequence distance L. Judging whether L is less than 0.015, if so, judging that the polarities of the grid-side current transformer and the neutral point current transformer are correct or all are connected reversely; otherwise, there is a polarity error phase.

And S3, the current of the target current phase in the I-type polarity error condition (A, B, C, AB, AC, BC, ABC and ABCN) is inverted, and the inverted current of the grid-side current transformer and the current of the neutral point current transformer are calculated. For two currents toSampling, calculating the longest common subsequence distance L of the two sampling sequences, and obtaining a distance set Q ═ L_A,L_B,L_C,L_AB,L_AC,L_BC,L_ABC,L_ABCD}. As shown in fig. 7, when the phase a of the grid-side current transformer is connected reversely and the neutral-point current transformer is connected reversely, the L values are all much larger than the threshold value in all the cases of traversing various polarities, and the L value is 0 in the case of only reverse BC connection, so it is determined that the BC connection is reverse in the class I case or the AN connection is reverse in the class II case.

S4, obtaining the three-phase current value i of the current transformer on the network side at the moment of unlocking the converter valve_a、i_bAnd i_cThree-phase voltage value u of converter transformer_a、u_bAnd u_cAnd three-phase current value i of valve-side current transformer_{VY_A}、i_{VY_B}And i_{VY_C}。

S5, pair i_bAnd i_cTaking the inverse to obtain the current

And

to i_a、

And

and u_a、u_bAnd u_cPerforming Clark transformation and inverse transformation. And calculating the instantaneous active power p of the current transformer on the network side by using the converted voltage value of the additional current, and judging the proportion of non-zero points in p. As shown in fig. 8, the instantaneous active power p oscillates and appears at AN obvious zero crossing point, and the proportion of the points greater than 0 in the instantaneous active power is much smaller than the threshold value, so that it is determined that the polarity is not the I-polarity case, but the II-polarity case, i.e., the AN is reversed.

S6, calculating

i_bAnd i_cIs compensated for current i_A、i_BAnd i_C. Respectively calculate i_AAnd i_{VY_A}，i_BAnd i_{VY_B}，i_CAnd i_{VY_C}Judging whether L is less than 0.015 or not, if so, judging that the phase polarity of the valve side current transformer is correct, and otherwise, judging that the polarity is wrong.

It should be understood that although the various steps in the flow charts of fig. 2-6 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 2-6 may include multiple steps or multiple stages, which are not necessarily performed at the same time, but may be performed at different times, which are not necessarily performed in sequence, but may be performed in turn or alternately with other steps or at least some of the other steps.

In one embodiment, as shown in fig. 9, there is provided a current transformer polarity verification apparatus, including: the device comprises an acquisition module, a determination module and a check module, wherein:

an obtaining module 901, configured to obtain current information of a network-side current transformer and current information of a neutral-point current transformer when the protection system is switched on in an idle state;

a determining module 902, configured to determine current waveform similarity between the grid-side current transformer and the neutral-point current transformer according to current information of the grid-side current transformer and current information of the neutral-point current transformer;

and the checking module 903 is configured to determine a current phase with an abnormal polarity from current phases corresponding to the grid-side current transformer and the neutral-point current transformer according to the current waveform similarity, and perform current polarity checking on the valve-side current transformer according to the current with the abnormal polarity.

In one embodiment, the determining module 902 is specifically configured to determine the first current sequence according to current information of the grid-side current transformer; the first current sequence comprises the sum of three-phase current values of the network side current transformer at different sampling moments; determining a second current sequence according to the current information of the neutral point current transformer; the second current sequence comprises current values of the neutral point current transformer at different sampling moments; and comparing current waveforms of the network side current transformer and the neutral point current transformer according to the first current sequence and the second current sequence to obtain current waveform similarity.

In one embodiment, the longest common subsequence of the first current sequence and the second current sequence is calculated, and the current waveform similarity is determined from the longest common subsequence.

In one embodiment, the checking module 903 is specifically configured to determine that the current polarities of the network-side current transformer and the neutral-point current transformer are both abnormal or both normal if the current waveform similarity is smaller than a preset similarity threshold; if the current waveform similarity is larger than a preset similarity threshold, performing polarity inversion processing on target current phases in the network side current transformer and the neutral point current transformer, and updating the current waveform similarity according to each phase current after the polarity inversion processing; and determining the current phase with abnormal polarity according to the updated current waveform similarity and a preset similarity threshold.

In one embodiment, one or more phases of the x-phase current of the grid-side current transformer and the y-phase current of the neutral-point current transformer are subjected to current phase polarity inversion processing; wherein, the polarities of the other current phases are not changed except for the polarity inversion treatment of the current phase; x and y are integers greater than or equal to 1.

In one embodiment, when a converter valve connected with a valve side current transformer is unlocked, current information and voltage information of a grid side current transformer and current information of the valve side current transformer are obtained; performing polarity inversion processing on the obtained current of the target current phase, and calculating the active power of the grid-side current transformer according to the current of the target current phase subjected to the polarity inversion processing and the currents of the other current phases of the grid-side current transformer; and determining the current phase with abnormal polarity as a target current phase or the rest phases of the network side current transformer according to the proportion of non-zero power in the active power of the network side current transformer.

In one embodiment, the checking module 903 is specifically configured to perform polarity inversion processing on the current phase with the abnormal polarity to obtain an inverted current value of the current phase with the abnormal polarity; performing compensation processing on the inverted current value and the current values of the other current phases of the network side current transformer, and judging whether the current values of all phases after the compensation processing are consistent with the polarity of the corresponding current phase of the valve side current transformer or not; and determining whether the polarity of each current phase of the valve side current transformer is abnormal or not according to the judgment result.

For specific limitations of the current transformer polarity verification apparatus, reference may be made to the above limitations of the current transformer polarity verification method, and details are not described here. All or part of each module in the current transformer polarity checking device can be realized by software, hardware and a combination thereof. The modules can be embedded in a hardware form or independent from a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.

In one embodiment, a computer device is provided, which may be a server, and its internal structure diagram may be as shown in fig. 10. The computer device includes a processor, a memory, and a network interface connected by a system bus. Wherein the processor of the computer device is configured to provide computing and control capabilities. The memory of the computer device comprises a nonvolatile storage medium and an internal memory. The non-volatile storage medium stores an operating system, a computer program, and a database. The internal memory provides an environment for the operation of an operating system and computer programs in the non-volatile storage medium. The database of the computer equipment is used for storing current information of a network side current transformer and a valve side current transformer and voltage information of a voltage transformer when the power system is switched on in an idle load mode and the converter valve is unlocked. The network interface of the computer device is used for communicating with an external terminal through a network connection. The computer program is executed by a processor to implement a current transformer polarity verification method.

Those skilled in the art will appreciate that the architecture shown in fig. 10 is merely a block diagram of some of the structures associated with the disclosed aspects and is not intended to limit the computing devices to which the disclosed aspects apply, as particular computing devices may include more or less components than those shown, or may combine certain components, or have a different arrangement of components.

In one embodiment, a computer device is provided, comprising a memory and a processor, the memory having a computer program stored therein, the processor implementing the following steps when executing the computer program:

under the condition that a protection system is switched on in an idle load mode, current information of a current transformer on the network side and current information of a current transformer at a neutral point are obtained;

determining the current waveform similarity of the grid-side current transformer and the neutral point current transformer according to the current information of the grid-side current transformer and the current information of the neutral point current transformer;

and determining a current phase with abnormal polarity from current phases corresponding to the grid side current transformer and the neutral point current transformer according to the current waveform similarity, and performing current polarity verification on the valve side current transformer according to the current with abnormal polarity.

In one embodiment, the processor, when executing the computer program, implements:

determining a first current sequence according to current information of the network side current transformer; the first current sequence comprises the sum of three-phase current values of the network side current transformer at different sampling moments; determining a second current sequence according to the current information of the neutral point current transformer; the second current sequence comprises current values of the neutral point current transformer at different sampling moments; and comparing current waveforms of the network side current transformer and the neutral point current transformer according to the first current sequence and the second current sequence to obtain current waveform similarity.

if the current waveform similarity is smaller than a preset similarity threshold, determining that the current polarities of the network side current transformer and the neutral point current transformer are both abnormal or both normal; if the current waveform similarity is larger than a preset similarity threshold, performing polarity inversion processing on target current phases in the network side current transformer and the neutral point current transformer, and updating the current waveform similarity according to each phase current after the polarity inversion processing; and determining the current phase with abnormal polarity according to the updated current waveform similarity and a preset similarity threshold.

when a converter valve connected with a valve side current transformer is unlocked, acquiring current information and voltage information of a network side current transformer and current information of the valve side current transformer; performing polarity inversion processing on the obtained current of the target current phase, and calculating the active power of the grid-side current transformer according to the current of the target current phase subjected to the polarity inversion processing and the currents of the other current phases of the grid-side current transformer; and determining the current phase with abnormal polarity as a target current phase or the rest phases of the network side current transformer according to the proportion of non-zero power in the active power of the network side current transformer.

carrying out polarity inversion processing on the current phase with abnormal polarity to obtain an inverted current value of the current phase with abnormal polarity; performing compensation processing on the inverted current value and the current values of the other current phases of the network side current transformer, and judging whether the current values of all phases after the compensation processing are consistent with the polarity of the corresponding current phase of the valve side current transformer or not; and determining whether the polarity of each current phase of the valve side current transformer is abnormal or not according to the judgment result.

In one embodiment, a computer-readable storage medium is provided, having a computer program stored thereon, which when executed by a processor, performs the steps of:

In one embodiment, the computer program when executed by the processor implements:

It will be understood by those skilled in the art that all or part of the processes of the methods of the embodiments described above can be implemented by hardware instructions of a computer program, which can be stored in a non-volatile computer-readable storage medium, and when executed, can include the processes of the embodiments of the methods described above. Any reference to memory, storage, database or other medium used in the embodiments provided herein can include at least one of non-volatile and volatile memory. Non-volatile Memory may include Read-Only Memory (ROM), magnetic tape, floppy disk, flash Memory, optical storage, or the like. Volatile Memory can include Random Access Memory (RAM) or external cache Memory. By way of illustration and not limitation, RAM can take many forms, such as Static Random Access Memory (SRAM) or Dynamic Random Access Memory (DRAM), among others.

The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.

The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A polarity verification method of a current transformer is applied to a protection system of a converter transformer, wherein the protection system comprises the converter transformer, a network side current transformer, a valve side current transformer and a neutral point current transformer, and is characterized by comprising the following steps:

under the condition that the protection system is switched on in an idle load mode, acquiring current information of the network side current transformer and current information of the neutral point current transformer;

determining the current waveform similarity of the grid side current transformer and the neutral point current transformer according to the current information of the grid side current transformer and the current information of the neutral point current transformer;

and determining a current phase with abnormal polarity from current phases corresponding to the grid side current transformer and the neutral point current transformer according to the current waveform similarity, and performing polarity verification on the current transformer on the valve side according to the current with abnormal polarity.

2. The method of claim 1, wherein determining the similarity of the current waveforms of the grid-side current transformer and the neutral-point current transformer according to the current information of the grid-side current transformer and the current information of the neutral-point current transformer comprises:

determining a first current sequence according to the current information of the network side current transformer; the first current sequence comprises the sum of three-phase current values of the grid-side current transformer at different sampling moments;

determining a second current sequence according to the current information of the neutral point current transformer; the second current sequence comprises current values of the neutral point current transformer at different sampling moments;

and comparing the first current sequence with the second current sequence to obtain the current waveform similarity.

3. The method of claim 2, wherein the comparing the current waveforms of the grid-side current transformer and the neutral-point current transformer according to the first current sequence and the second current sequence to obtain the current waveform similarity comprises:

calculating the longest common subsequence of the first current sequence and the second current sequence, and determining the current waveform similarity according to the longest common subsequence.

4. The method according to claim 1, wherein the determining the current phase with abnormal polarity from the currents corresponding to the grid-side current transformer and the neutral-point current transformer according to the current waveform similarity comprises:

if the current waveform similarity is smaller than a preset similarity threshold, determining that the current polarities of the network side current transformer and the neutral point current transformer are both abnormal or both normal;

if the current waveform similarity is larger than the preset similarity threshold, performing polarity inversion processing on target current phases in the network side current transformer and the neutral point current transformer, and updating the current waveform similarity according to each phase current after the polarity inversion processing;

and determining the current phase with abnormal polarity according to the updated current waveform similarity and the preset similarity threshold.

5. The method of claim 4, wherein the inverting the current phase polarity of the grid-side current transformer and the neutral-point current transformer comprises:

performing current phase polarity inversion processing on one phase or multiple phases in the x-phase current of the grid-side current transformer and the y-phase current of the neutral point current transformer; the polarities of the other current phases except the current phase polarity inversion treatment are unchanged; and x and y are integers which are more than or equal to 1.

6. The method according to claim 4, wherein the determining the current phase with the abnormal polarity according to the updated current waveform similarity and the preset similarity threshold comprises:

when a converter valve connected with the valve side current transformer is unlocked, acquiring current information and voltage information of the grid side current transformer and current information of the valve side current transformer;

performing polarity inversion processing on the obtained current of the target current phase, and calculating active power of the grid-side current transformer according to the current of the target current phase subjected to the polarity inversion processing and currents of the other current phases of the grid-side current transformer;

and determining the current phase with the abnormal polarity as the target current phase or the rest phases of the network side current transformer according to the proportion of non-zero power in the active power of the network side current transformer.

7. The method of claim 1, wherein the polarity checking of the current according to the polarity abnormality with respect to the valve-side current transformer comprises:

carrying out polarity inversion processing on the current phase with the abnormal polarity to obtain an inverted current value of the current phase with the abnormal polarity;

performing compensation processing on the inverted current value and current values of other current phases of the network side current transformer, and judging whether the current values of all phases after compensation processing are consistent with the polarity of the corresponding current phase of the valve side current transformer or not;

and determining whether the polarity of each current phase of the valve side current transformer is abnormal or not according to the judgment result.

8. A current transformer polarity verification device, characterized in that the device comprises:

the acquisition module is used for acquiring current information of the network side current transformer and current information of the neutral point current transformer under the condition that the protection system is switched on in an idle load mode;

the determining module is used for determining the current waveform similarity of the grid side current transformer and the neutral point current transformer according to the current information of the grid side current transformer and the current information of the neutral point current transformer;

and the checking module is used for determining a current phase with abnormal polarity from current phases corresponding to the grid side current transformer and the neutral point current transformer according to the current waveform similarity, and performing current polarity checking on the valve side current transformer according to the current with abnormal polarity.

9. A computer device comprising a memory and a processor, the memory storing a computer program, characterized in that the processor, when executing the computer program, implements the steps of the method of any of claims 1 to 7.

10. A computer-readable storage medium, on which a computer program is stored, which, when being executed by a processor, carries out the steps of the method of any one of claims 1 to 7.