A distribution network differential protection synchronization method and device based on pseudo-random sequence

Abstract

The present invention discloses a distribution network differential protection synchronization method based on a pseudo-random sequence. The method comprises the following steps: S1: loading a carrier sequence model for confirming synchronization of a current transformer; the carrier sequence model comprises a PN sequence model using a PN sequence as a pseudo-random sequence; S2: propagating the PN sequence model to the current transformer at the power transmission end via a base station, whereby the current transformers at different locations at the power transmission end extract the PN sequence model at the same sampling rate; S3: performing a synchronization determination on the PN sequence model extracted in step S2; and S4: based on the determination result of step S3, if synchronization is achieved, differential protection is performed on the power transmission end; if not, asynchronous time difference identification is performed to achieve a rapid synchronization response, completing synchronization, and performing differential protection. The present invention utilizes the good autocorrelation of the PN sequence to enable synchronization determination for current transformers at different locations.

Description

Technical Field

[0001] The present invention relates to the field of distribution differential protection methods, and in particular to a distribution network differential protection synchronization method and device based on a pseudo-random sequence. Background Art

[0002] In power differential protection applications, data synchronization between the protected ends is crucial to ensure reliable operation of the differential protection system. Currently used synchronization technologies can be broadly categorized into two types: data channel-based synchronization and Global Positioning System (GPS)-synchronized clock synchronization. Current data channel synchronization methods rely on ping-pong timing, supplemented by reference vector timing. This method assumes a known line structure. Clock difference synchronization is used to synchronize line current samples. This method assumes a known line structure and suffers from limited synchronization accuracy. Alternatively, fiber differential protection data synchronization is achieved using a difference-based method. This method linearly differs between two sampling points before and after the sampling point. This method relies on the location of the sampling points and can easily produce errors if multiple sampling points deviate. GPS-synchronized clock synchronization utilizes satellite timing. While highly accurate, it requires GPS timing equipment and is easily affected by external factors such as weather and terrain, requiring significant resources. Summary of the Invention

[0003] The technical problem to be solved by the present invention is that the existing time synchronization means cannot achieve good synchronization effect in differential protection. The purpose is to provide a distribution network differential protection synchronization method and device based on pseudo-random sequence, which utilizes the good autocorrelation of PN sequence to enable current transformers at different positions to obtain PN sequence, and synchronously identify the respectively obtained PN sequences. If synchronization is achieved, the process is completed; if not, the asynchronous time difference is identified and rapid synchronization is performed.

[0004] The present invention is achieved through the following technical solutions:

[0005] A distribution network differential protection synchronization method based on pseudo-random sequence, the method comprising the steps of:

[0006] S1: loading a carrier sequence model for synchronizing and confirming the current transformer; the carrier sequence model includes a PN sequence model using a PN sequence as a pseudo-random sequence;

[0007] S2: The PN sequence model is propagated to the current transformer at the power transmission end through the base station. The current transformers at different locations at the power transmission end extract the PN sequence model at the same sampling rate.

[0008] S3: Synchronize and judge the PN sequence model extracted in step S2 above;

[0009] S4: Based on the judgment result of the above step S3, if synchronization is achieved, differential protection is performed on the power transmission end; if not, asynchronous time difference identification is performed to perform rapid synchronization response, complete synchronization, and perform differential protection.

[0010] Furthermore, in step S3, different power transformers synchronously identify the PN sequence model through 5G signals.

[0011] Furthermore, before loading the carrier sequence model in step S1, the process also includes generating a PN sequence model.

[0012] Furthermore, the method of generating the PN sequence model is:

[0013] For a prime number p, select a prime number sequence set A={a 0 ,a 1 ,...a p-2},in

[0014]

[0015] For a positive integer n, choose the trace function tr(x) from GF(q) to GF(p), where q = p n ; Let α be the generator in GF(q), generating the sequence

[0016]

[0017] Where i = 0, 1, ..., p-2;

[0018] Choose a mapping from (GF(p), GF(p)) to the integer ring Function f(x,y) to construct a new PN sequence

[0019]

[0020] in,

[0021] in,

[0022] GF(q): represents a finite field containing q elements;

[0023] α: represents a generator of GF(q);

[0024] tr(x): trace function from GF(q) to GF(p), where q = p n ;

[0025] Z q : represents an integer ring containing q elements;

[0026] <x> n : represents the remainder of x modulo n;

[0027] h(x,y): If x=y, then h(x,y)=1; if x≠y, then h(x,y)=0.

[0028] Furthermore, the synchronization determination method in step S3 is: let the value range of the time constant τ be 0≤τ≤p n -1; using the autocorrelation of the PN sequence, obtain its autocorrelation value; when the autocorrelation value can reach the maximum value p n When , the PN sequence model completes synchronization.

[0029] Furthermore, in step S4, the time difference between the PN sequence model and itself is set to d sequence elements; the method for determining the asynchronous time difference is:

[0030] When a first PN sequence and a second PN sequence exist between any two current transformers, and the first PN sequence is obtained by cyclically left-shifting the second PN sequence by d positions, an asynchronous time difference exists between the two current transformers.

[0031] Furthermore, in step S4, the asynchronous time difference d is calculated by subtracting the PN sequence information in the PN sequence model extracted by sampling the current transformer from the shift sequence itself.

[0032] Furthermore, in step S4, the rapid synchronization response method of the asynchronous time difference is: the PN sequence model obtained by sampling the current transformer with asynchronous time difference is shifted right by d positions to obtain the PN sequence information in the PN sequence model, and synchronized to complete rapid timing and synchronization with other current transformers.

[0033] On the other hand, the present invention also provides a distribution network differential protection synchronization device based on a pseudo-random sequence, comprising:

[0034] A preloading module, the preloading module is used to load a pre-generated carrier sequence model in the base station, the carrier sequence model includes a PN sequence model using a PN sequence as a pseudo-random sequence;

[0035] Interaction sampling module, the interaction sampling module is set on the current transformer, connected to the base station for sampling and extracting the PN sequence model;

[0036] Asynchronous synchronization module, the asynchronous synchronization module is used to quickly respond to different current transformers according to the PN sequence model.

[0037] Furthermore, it also includes a PN sequence generation module.

[0038] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0039] The PN sequences generated by the method of the present invention are multiple PN sequences. In the present invention, the trace function tr(x) is selected to generate the PN sequence. Because the sequence generated by the trace function tr(x) has good periodicity, it is itself a pseudo-random sequence. In the present invention, the sequence generated by the trace function tr(x) is a pseudo-random sequence and a subsequence of the PN sequence. By establishing a relationship between the trace function tr(x) and the PN sequence, the PN sequence can utilize the good periodicity of the sequence generated by the trace function tr(x) to facilitate synchronization checks and achieve rapid synchronization responses during asynchronous operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present invention, the following briefly introduces the drawings required for use in the examples. It should be understood that the following drawings only illustrate certain embodiments of the present invention and should not be considered as limiting the scope. A person of ordinary skill in the art can also derive other relevant drawings based on these drawings without inventive effort. In the drawings:

[0041] Figure 1 The present invention provides a flow chart of a distribution network differential protection synchronization method based on pseudo-random sequences. DETAILED DESCRIPTION

[0042] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The exemplary embodiments of the present invention and their descriptions are only used to explain the present invention and are not intended to limit the present invention.

[0043] Example 1

[0044] The present invention proposes a new synchronization method for differential protection of power distribution networks, namely, a synchronization mechanism based on a PN sequence as a carrier sequence. If synchronized, the system is complete. If not, in order to achieve rapid synchronization response, it is required that the PN sequences be able to identify asynchronous time differences, so that time synchronization and synchronization can be performed quickly. A new PN sequence is constructed to perform synchronization identification, achieving rapid response and rapid time synchronization for differential protection. The constructed PN sequence can achieve: strict synchronization judgment function, thus ensuring high synchronization accuracy; the ability to identify asynchronous time differences, so that time synchronization and synchronization can be performed quickly, with rapid response; the PN sequence has good pseudo-randomness and can resist interference and interception. The present invention is achieved through the following steps:

[0045] See also Figure 1 A distribution network differential protection synchronization method based on a pseudo-random sequence, the method comprising the steps of:

[0046] S1: Loading a carrier sequence model for synchronization confirmation of the current transformer; the carrier sequence model includes a PN sequence model that uses a PN sequence as a pseudo-random sequence. The carrier sequence is loaded at the base station, which transmits the carrier sequence to the current transformer at the power transmission end via a 5G signal. The carrier sequence model in this embodiment is a digital mathematical model.

[0047] S2: The PN sequence model is transmitted via the base station to the current transformers at the power transmission end. Current transformers at different locations at the power transmission end extract the PN sequence model at the same sampling rate. In this embodiment, the carrier sequence transmitted in step S1 is a single signal. Therefore, for synchronization, a control variable is required. Specifically, the PN sequence model is sampled at the same sampling rate. This ensures that the PN sequences sampled by the current transformers are synchronized under the desired conditions.

[0048] S3: Perform synchronization judgment on the PN sequence model extracted in the above step S2.

[0049] S4: Based on the judgment result of the above step S3, if synchronization is achieved, differential protection is performed on the power transmission end; if not, asynchronous time difference identification is performed to perform rapid synchronization response, complete synchronization, and perform differential protection.

[0050] Through the above method and steps, different current transformers located on different branches of the power transmission end, or at different levels, can be synchronously identified using the PN sequence model sent by the base station, and differential protection is then implemented based on the results of the synchronous identification. This signal transmission maximizes the scope and effectiveness of differential protection.

[0051] In order to achieve the above effect, the embodiment also includes the generation of a PN sequence model before loading the carrier sequence model. Figure 1 In this embodiment, the PN sequence generation process includes the trace function tr(x). This allows the trace function tr(x) to have good periodicity, thereby reducing the time consumption during synchronization checking. The PN sequence model is generated as follows:

[0052] For a prime number p, select a prime number sequence set A={a 0 ,a 1 ,...a p-2 }in

[0053]

[0054] Frequency hopping technology is often used as a signal transmission method in power communication. The advantage of selecting prime numbers in this embodiment is that the prime number sequence set generated by prime numbers is used as the frequency hopping, which has a uniform interval and can avoid the delay caused by numerical redundancy during synchronization judgment. <x> n It represents the remainder of x modulo n, that is, when used, multiple PN sequences are generated. The generation rule of multiple PN sequences is to use the remainder class calculation of the modulus, and the elements in the original formula are divided by n, that is, p in this formula, to take the remainder for calculation.

[0055] After that, a subsequence of the desired PN sequence is generated, that is, for a positive integer n, a trace function tr(x) from GF(q) to GF(p) is selected, where q = p n Let α be the generator in GF(q), generating the sequence

[0056]

[0057] Where i = 0, 1, ..., p-2;

[0058] Where GF(q): represents a finite field containing q elements; α: represents a generator of GF(q); tr(x): the trace function from GF(q) to GF(p), where q = p n .

[0059] In conventional usage, PN sequence can be generated without using trace function. However, since the sequence generated by trace function has good periodicity, its distribution is regular and also satisfies the pseudo-random sequence, the PN sequence constructed by using trace function also has good pseudo-randomness and better periodicity, making synchronization judgment faster and more convenient. i Then, select the mapping from (GF(p), GF(p)) to the integer ring Function f(x,y) to construct a new PN sequence

[0060]

[0061] in,

[0062] The superscript i represents the PN sequence number, and the subscript j represents the element number in the generated PN sequence. This allows the PN sequence model to be loaded before the base station transmits the carrier sequence model. Once the base station loads the generated PN sequence model into the carrier sequence model, transmission to the current transformer at the power transmission end can begin.

[0063] In step S3, the synchronization determination method is: let the value range of the time constant τ be 0≤τ≤p n -1; using the autocorrelation of the PN sequence, obtain its autocorrelation value; when the autocorrelation value can reach the maximum value p n When , the PN sequence model completes synchronization. Specifically, the method for determining the synchronization of a single current transformer to a PN sequence is: let h(x,y) represent if x=y, then h(x,y)=1, if x≠y, then h(x,y)=0, then the autocorrelation function of the PN sequence is

[0064]

[0065] Since f(x,y) is the integer ring from (GF(p),GF(p)) One-to-one mapping, so

[0066]

[0067] The purpose of this formula is to calculate the value of the digital element in the PN sequence by summing the functions of the PN sequence autocorrelation. Any current transformer can quickly calculate the number of corresponding bits that are the same by collecting the PN sequence. Then, by summing and comparing the sums, it can quickly determine whether the collected PN sequences are consistent. If they are consistent, it means that the synchronization is successful. At the same time, since 1≤i+1≤p-1, it is obvious that only when τ=0,p,2p,...,p n -p, <-(i+1)τ> p = 0. And τ = 0,p,2p,...,p n -p, only when τ=0 can tr(α j (1-α τ )) is always 0. It can be seen that when the sequence is strictly synchronized with the sequence itself, its autocorrelation value can reach the maximum value p n , that is, it has strict synchronization judgment function.

[0068] According to the result of the synchronization judgment in the above steps, if there is no synchronization, fast synchronization is required. The fast synchronization is manifested in that the PN sequences of different current transformers are consistent. Therefore, in the process of unifying the synchronous PN sequence and the asynchronous PN sequence, assuming that in sequence c i The time difference from its own asynchronous state is d sequence elements, where the sequence element refers to the relative position of the elements in a single PN sequence string. The sequence obtained by circularly shifting left by d bits Asynchronous with the original sequence, we can assume that g(x) is the inverse function of f(x,y). Any sequence element in 0≤j≤p n -1, and its corresponding asynchronous sequence element is Compare and Available and

[0069] By comparison and Available

[0070]

[0071] It can be seen that the difference is only a multiple of -(i+1) with the asynchronous time difference d. Therefore, the time difference d can be obtained by dividing the difference by -(i+1). Then, the synchronous sequence can be obtained by cyclically shifting the asynchronous sequence to the right by d bits, completing fast timing and synchronization. Differential protection can be performed on the current transformers at the power transmission end that receive the same PN sequence.

[0072] Furthermore, since the sequence generated by the trace function tr(x) is a pseudo-random sequence and the pseudo-random sequence is sequence c i subsequence of , so c i It also has good pseudo-randomness. At the same time, since the value of i is 0, 1, 2, ..., p-2, even if the formula for calculating the time difference is <-(i+1)d> p After deciphering the division by -(i+1), different formulas can be selected for different i, significantly enhancing security and resisting interference and interception. This security is achieved by generating and expressing inverse and trace functions. Even if a single PN sequence is intercepted or interfered with, the PN sequence model includes multiple PN sequences distinguished by the superscript i. In the event of interference or interception, another PN sequence can be immediately selected within the PN sequence model to continue synchronous checking and asynchronous response, thereby improving system stability.

[0073] Example 2

[0074] A PN sequence model, including the PN sequence model generation method and asynchronous synchronization method as described in Example 1, wherein p=7, q=p 2 =49, generate a sequence of prime numbers

[0075] a 0 =(0,1,2,3,4,5,6)

[0076] a 1 =(0,2,4,6,1,3,5)

[0077] a 2 =(0,3,6,2,5,1,4)

[0078] a 3 =(0,4,1,5,2,6,3)

[0079] a 4 =(0,5,3,1,6,4,2)

[0080] a 5 =(0,6,5,4,3,2,1)

[0081] Using the trace function tr(x) from GF(q) to GF(p), we can get

[0082] tr(α 0 )=0,tr(α 1 )=6,tr(α 2 )=6,tr(α 3 )=1,

[0083] tr(α 4 )=3,tr(α 5 )=1,tr(α 6 )=2,……

[0084] Select the one-to-one mapping function f(x,y)=xp+y to get the following PN sequence

[0085] c 0 =(0,13,20,22,31,36,44,…)

[0086] c 1 =(0,20,34,43,10,22,37,…)

[0087] c 2 =(0,27,48,15,38,8,30,…)

[0088] c 3 =(0,34,13,36,17,43,23,…)

[0089] c 4 =(0,41,27,8,45,29,16,…)

[0090] c 5 =(0,48,41,29,24,15,9,…)

[0091] Assume that the sequence c 1 , if there is a time difference d = 3, then the corresponding asynchronous sequence is (43, 10, 22, 37, ...), select the same as c 1 The corresponding bit 34 of f(x,y) is operated, that is, 22 and 34 are operated, which can be calculated using the inverse function g(x) of f(x,y)

[0092] g(22)=(3,1)

[0093] g(34)=(4,6)

[0094] Using the formula That is, there is a time difference of d = |-3| = 3. Therefore, the asynchronous sequence can be synchronized by shifting it right by -3 bits (shifting it left by 3 bits).

[0095] Example 3

[0096] A pseudo-random sequence-based distribution network differential protection synchronization device includes the pseudo-random sequence-based distribution network differential protection synchronization method described in Example 1, and further includes a preloading module for loading a pre-generated carrier sequence model into a base station, wherein the carrier sequence model includes a PN sequence model that uses a PN sequence as a pseudo-random sequence. An inter-sensitivity sampling module is provided on a current transformer and is communicatively connected to the base station for sampling and extracting the PN sequence model. An asynchronous synchronization module is configured to execute the steps of the pseudo-random sequence-based distribution network differential protection synchronization method described in Example 1, and to rapidly synchronize different current transformers according to the PN sequence model. Furthermore, the device further includes a PN sequence generation module for generating the PN sequence model.

[0097] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.< / x> < / x>

Claims

1. A distribution network differential protection synchronization method based on pseudo-random sequence, characterized in that: The method comprises the steps of: S1: loading a carrier sequence model for synchronizing and confirming the current transformer; the carrier sequence model includes a PN sequence model using a PN sequence as a pseudo-random sequence; S2: Propagating the PN sequence model to the current transformer located at the power transmission end through the base station, so that the current transformers located at different positions of the power transmission end respectively extract the PN sequence model at the same sampling rate; S3: Performing synchronous judgment on the PN sequence model extracted in step S2 above; S4: Based on the judgment result of the above step S3, if synchronization is achieved, differential protection is performed on the power transmission end; if not, asynchronous time difference identification is performed to perform rapid synchronization response, complete synchronization, and perform differential protection; In step S4, let the time difference between the PN sequence model and itself be d The asynchronous time difference is determined as follows: when there is a first PN sequence and a second PN sequence between any two current transformers, the first PN sequence is a cyclic left shift of the second PN sequence. d The asynchronous time difference is calculated by subtracting the PN sequence information in the PN sequence model extracted by sampling the current transformer from its own shift sequence. d ; In step S4, the rapid synchronous response method of the asynchronous time difference is: cyclically shifting the PN sequence model obtained by sampling the current transformer with the asynchronous time difference to the right d The PN sequence information in the PN sequence model can be obtained by the bit, and synchronization is performed to complete fast time synchronization and synchronization with other current transformers.

2. A distribution network differential protection synchronization method based on pseudo-random sequence according to claim 1, characterized in that: In step S3, different current transformers synchronously identify the PN sequence model through 5G signals.

3. The method for synchronizing distribution network differential protection based on pseudo-random sequence according to claim 1, characterized in that: Before step S1 of loading the carrier sequence model, the step further includes generating the PN sequence model.

4. A distribution network differential protection synchronization method based on pseudo-random sequence according to claim 3, characterized in that: The PN sequence model is generated as follows: For a prime number p, select a prime number sequence set A = {a 0 , a 1 ,...a p-2 },in ； For a positive integer n, choose the trace function tr(x) from GF(q) to GF(p), where q = p n ;set up is a generator in GF(q), generating the sequence Where i=0, 1, ..., p-2; Choose a mapping from (GF(p), GF(p)) to the ring of integers Function f (x, y) to construct a new PN sequence , i = 0,1,...,p-2; in, ,i=0,1,…,p-2;j=0,1…,p n -1; in, GF(q): represents a finite field containing q elements; :represents a generator of GF(q); tr(x): trace function from GF(q) to GF(p), where q = p n ; Z q : represents an integer ring containing q elements; : represents the remainder of x modulo n.

5. A distribution network differential protection synchronization method based on pseudo-random sequence according to claim 4, characterized in that: The synchronization determination method in step S3 is: let the time constant The value range is ; Using the autocorrelation of the PN sequence, obtain its autocorrelation value; when the autocorrelation value can reach the maximum value p n When , the PN sequence model completes synchronization.

6. A distribution network differential protection synchronization device based on pseudo-random sequence according to claim 1, characterized in that: The method for synchronizing distribution network differential protection based on a pseudo-random sequence according to claims 1 to 5 further comprises: A preloading module, configured to load the pre-generated carrier sequence model into the base station, the carrier sequence model including the PN sequence model using the PN sequence as a pseudo-random sequence; An inter-sensing sampling module, the inter-sensing sampling module is arranged on the current transformer, is communicatively connected with the base station, and is used for sampling and extracting the PN sequence model; An asynchronous synchronization module is used to perform fast response synchronization on different current transformers according to the PN sequence model.

7. A distribution network differential protection synchronization device based on pseudo-random sequence according to claim 6, characterized in that: It also includes a PN sequence generation module.

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