A method for characteristic current synchronization and orientation in substation area topology sorting

Abstract

The present invention relates to the field of power frequency communication technology, and discloses a method for feature current synchronization and orientation for substation area topology sorting, which includes the following steps: the sending end generates a feature current signal, including a synchronization sequence and a direction determination sequence; the sending end sends the synchronization sequence at the power frequency zero crossing, and immediately sends the direction determination sequence after sending; the receiving end samples the current signal and performs difference calculation for adjacent power frequency cycles; a sliding window is used to perform correlation calculation on the sampled current signal: if the calculated correlation value reaches a preset threshold, it indicates that signal synchronization is completed; the receiving end sums the sampling points of the direction determination sequence after the synchronization signal, and judges the current direction according to the positive or negative of the summation result. By adding a direction determination sequence with an effective frequency component of low frequency after the synchronization sequence, performing adjacent cycle difference and summation calculations at the receiving end, and judging the direction of the feature current according to the summation result, the present invention avoids the influence of shunt and phase shift, and ensures the accuracy of substation area topology sorting.

Description

Technical Field

[0001] The present invention relates to the technical field of power frequency communication, and particularly to a method for synchronizing and orienting characteristic currents for substation area topology sorting. Background Art

[0002] Power line power frequency communication technology realizes communication between different devices on the power grid by superimposing characteristic currents with specified frequencies or waveforms on the power frequency current, and judges the position of the device in the power grid by identifying the direction of the characteristic current, so as to realize the topology sorting of the low-voltage substation area, which is of great significance to distribution automation. However, the load types in the low-voltage substation area are relatively complex, especially there are a large number of capacitive loads, which cause phase shift and shunt phenomena of the characteristic current.

[0003] The key to realizing the topology sorting of the low-voltage substation area is to successfully identify the synchronization signal and the direction of the characteristic current is correct. The current synchronization method mainly relies on performing correlation calculations on the m-sequence, and judges the direction of the characteristic current by the positive and negative of the correlation value. However, the frequency domain of the m-sequence is relatively wide, and when there are a large number of capacitive loads in the power grid, high-frequency components are prone to shunt and phase shift, especially the phase shift is likely to cause the positive and negative of the correlation value to be opposite to the actual direction. Summary of the Invention

[0004] In view of the deficiencies and defects existing in the prior art, the present invention provides a method for synchronizing and orienting characteristic currents for substation area topology sorting. By adding a direction determination sequence with an effective low-frequency component after the synchronization sequence, adjacent power frequency cycles are subtracted and summed at the receiving end, and the direction of the characteristic current is judged by the positive and negative of the summation result, so as to avoid the influence caused by shunt and phase shift.

[0005] The object of the present invention can be achieved by the following technical solutions:

[0006] A method for synchronizing and orienting characteristic currents for substation area topology sorting includes the following steps:

[0007] Step 1: The transmitting end generates a characteristic current signal, including a synchronization sequence and a direction determination sequence;

[0008] Step 2: The transmitting end sends the synchronization sequence at the power frequency zero crossing, and immediately sends the direction determination sequence after sending;

[0009] Step 3: The receiving end samples the current signal and performs subtraction of adjacent power frequency cycles;

[0010] Step 4: Perform correlation calculation on the sampled current signal by using a sliding window: if the calculated correlation value reaches a preset threshold, it means that signal synchronization is completed, and jump to Step 5; otherwise, jump to Step 1 to execute the process again;

[0011] Step 5: The receiving end sums up the sampling points of the direction determination sequence after synchronization, and determines the current direction according to the positive or negative of the summation result.

[0012] Further, the synchronization sequence adopts an m-sequence, which is spread spectrum and then switched to the power frequency current.

[0013] Further, for the direction determination sequence:

[0014] The duration selection range is from 0.5 second to 2 seconds;

[0015] The amplitude selection range of the characteristic current signal is 10 mA to 400 mA, the switching frequency selection range of the characteristic current signal is 250 Hz to 1000 Hz, and the duty cycle selection range is 1 / 10 to 9 / 10;

[0016] The time that simultaneously satisfies the following three conditions is the switching time of the characteristic current:

[0017] Condition 1, the amplitude of the power frequency odd-cycle current is greater than 0;

[0018] Condition 2, the amplitude of the power frequency even-cycle current is less than 0;

[0019] Condition 3, the phases of the two sections of current described in Condition 1 and Condition 2 differ by 180°.

[0020] Further, the formula for taking the difference between adjacent power frequency cycles in Step 3 is:

[0021]

[0022] In the above formula, I is the current data after taking the difference between adjacent power frequency cycles, is the power frequency current of the k-th cycle.

[0023] Further, in Step 5, the formula for summing up the sampling points of the direction determination sequence is:

[0024]

[0025] In the above formula, I i is the current data of the i-th sampling point after taking the difference between adjacent power frequency cycles; N is the number of sampling points in one power frequency cycle; kN is the total number of sampling points in k cycles;

[0026] When the summation result y value is positive, the direction of the characteristic current is the positive direction; when the summation result y value is less than or equal to zero, the direction of the characteristic current is the reverse direction.

[0027] Advantageous technical effects of the present invention: 1. The effective frequency component of the characteristic current is low-frequency, which is not prone to shunt, ensuring that the attenuation of the characteristic current at the receiving end is small; 2. The low-frequency component of the characteristic current is not prone to phase shift when there are many capacitive loads, which is beneficial to the correct judgment of the direction of the characteristic current, and thus ensures the accuracy of the topological sorting of the power distribution area. Description of the Drawings

[0028] Figure 1 It is the overall flowchart of the present invention.

[0029] Figure 2 It is the current waveform of the direction determination sequence initially generated in the embodiment of the present invention.

[0030] Figure 3 It is the current waveform of the direction determination sequence after taking the difference between adjacent power frequency cycles in the embodiment of the present invention. Detailed Embodiment

[0031] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

[0032] Embodiment:

[0033] Combined with the attached Figure 1 , a method for synchronizing and orienting characteristic currents for topological sorting of a power distribution area includes the following steps:

[0034] Step 1: The HPLC module generates a characteristic current signal, including a synchronization sequence A and a direction determination sequence B;

[0035] The synchronization sequence A is an m-sequence with 4094 bits after spreading spectrum, which is switched onto the power frequency current.

[0036] The duration of the direction determination sequence B is 1 second, the amplitude of the characteristic current signal is 200 mA, the switching frequency of the characteristic current signal is 500 Hz, the duty cycle is 7 / 10, and the switching time of the characteristic current is the time that simultaneously satisfies the following 3 conditions:

[0037] Condition 1, the amplitude of the power frequency odd-cycle current is greater than 0;

[0038] Condition 2, the amplitude of the power frequency even-cycle current is less than 0;

[0039] Condition 3, the phases of the two sections of current described in Condition 1 and Condition 2 differ by 180°.

[0040] The current waveform of the direction determination sequence B generated in the embodiment is as Figure 2 shown.

[0041] Step 2: The HPLC module sends synchronization sequence A at the zero crossing of the power frequency. Immediately after sending, it sends direction determination sequence B.

[0042] Step 3: The intelligent circuit breaker samples the current signal and performs a difference operation between adjacent power frequency cycles to remove the power frequency current. The formula for the difference operation between adjacent power frequency cycles is:

[0043]

[0044] In the above formula, I is the current data after the difference operation between adjacent power frequency cycles, is the power frequency current of the k-th cycle.

[0045] In the embodiment, the current waveform of direction determination sequence B after the difference operation between adjacent power frequency cycles is as Figure 3 shown.

[0046] Step 4: Use a sliding window to calculate the correlation of the sampled current signal: When the calculated correlation value reaches the preset threshold, it indicates that signal synchronization is completed, and then jump to Step 5.

[0047] Step 5: The intelligent circuit breaker sums the sampling points of direction determination sequence B after synchronization sequence A. The summation formula is:

[0048]

[0049] In the above formula, I i is the current data of the i-th sampling point after the difference operation between adjacent power frequency cycles; N is the number of sampling points in one power frequency cycle; kN is the total number of sampling points in k cycles.

[0050] In the embodiment, the calculated summation result y = 503 A. Therefore, the characteristic current direction is positive, which is consistent with the actual characteristic current direction. The theoretical value of this result is 560 A, and the shunt and attenuation are only about 10%.

[0051] The above embodiments are illustrative of the specific implementation manners of the present invention, rather than limitations thereof. Those skilled in the relevant technical fields can make various transformations and changes without departing from the spirit and scope of the present invention to obtain corresponding equivalent technical solutions. Therefore, all equivalent technical solutions should be included in the patent protection scope of the present invention.

Claims

1. A method for characteristic current synchronization and orientation in substation area topology sorting, characterized in that It includes the following steps: Step 1: The sending end generates a characteristic current signal, including a synchronization sequence and a direction determination sequence; Step 2: The sending end sends the synchronization sequence at the zero-crossing point of the power frequency, and immediately sends the direction determination sequence after sending it; Step 3: The receiving end samples the current signal and makes a difference between adjacent power frequency cycles; Step 4: Use a sliding window to calculate the correlation of the sampled current signal: If the calculated correlation value reaches the preset threshold, it means that the signal synchronization is completed, and jump to Step 5; Otherwise, jump to Step 1 and execute the process again; Step 5: The receiving end sums the sampled point current data of the direction determination sequence after making a difference between adjacent power frequency cycles, and judges the current direction according to the positive or negative of the summation result.

2. A method for synchronizing and orienting characteristic currents for busbar area topology sorting according to claim 1, characterized in that, The synchronization sequence uses an m-sequence and is switched to the power frequency current after spreading spectrum.

3. The characteristic current synchronization and orientation method for substation area topology sorting according to claim 1, wherein, For the direction determination sequence: The selected range of its duration is 0.5 seconds to 2 seconds; The selected range of the amplitude of the characteristic current signal is 10 mA to 400 mA, the selected range of the switching frequency of the characteristic current signal is 250 Hz to 1000 Hz, and the selected range of the duty cycle is 1 / 10 to 9 / 10; The time that simultaneously satisfies the following 3 conditions is the switching time of the characteristic current: Condition 1, the amplitude of the current in the odd power frequency cycle is greater than 0; Condition 2, the amplitude of the current in the even power frequency cycle is less than 0; Condition 3, the phases of the two sections of current described in Condition 1 and Condition 2 differ by 180°.

4. A method for characteristic current synchronization and orientation in substation area topology sorting according to claim 1, characterized in that, The formula for making a difference between adjacent power frequency cycles in Step 3 is: In the above formula, I is the current data after taking the difference between adjacent power frequency cycles, and is the power frequency current of the k-th cycle.

5. A method for feature current synchronization and orientation in substation area topology sorting according to claim 1, characterized in that, In Step 5, the formula for summing the sampled points of the direction determination sequence is: In the above formula, I i is the current data of the i-th sampling point after taking the difference between adjacent power frequency cycles; N is the number of sampling points in one power frequency cycle; kN is the total number of sampling points in k cycles; When the summation result y value is positive, the direction of the characteristic current is the positive direction; when the summation result y value is less than or equal to zero, the direction of the characteristic current is the reverse direction.

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