Fault detection method, medium and system for wireless data collection and conversion stations

Abstract

The present invention discloses a fault detection method, medium and system for wireless data collection between converter stations, including: collecting the traveling wave voltage of the fault current of the DC transmission line between the converter stations at preset intervals; respectively calculating the absolute value of the first difference between the traveling wave voltage of the positive line collected this time and the traveling wave voltage of the positive line collected last time, and the absolute value of the second difference between the traveling wave voltage of the negative line collected this time and the traveling wave voltage of the negative line collected last time; if the absolute value of the first difference and / or the absolute value of the second difference is greater than the first threshold, respectively calculating the positive polarity torsion of the traveling wave voltage of the positive line collected this time and the negative polarity torsion of the traveling wave voltage of the negative line collected this time; according to the magnitude relationship between the positive polarity torsion and the negative polarity torsion and the second threshold, respectively, determining the fault position of the DC transmission line between the converter stations. The present invention is not easily interfered and is easy to identify terminal high-resistance faults and near-end faults.

Description

Technical Field

[0001] The present invention relates to the technical field of fault detection of DC transmission lines between converter stations, and in particular to a fault detection method, medium and system for converter stations with wireless data collection. Background Art

[0002] DC transmission is mainly used for ultra-long-distance and ultra-large-capacity power transmission projects of large energy bases. The development of high-voltage and ultra-high-voltage DC transmission technology is an effective means to solve China's new energy consumption and long-distance and large-scale power transmission problems. High-voltage DC (LCC-HVDC) transmission technology based on thyristor converters has been widely used in long-distance and large-capacity power transmission in recent years. The safety of converters and their lines, which are important equipment in DC transmission systems, is seriously threatened. The lockout of converter stations will bring huge economic losses to the power system. Therefore, the reliability of fault detection schemes between converter stations, especially their line detection schemes, must be guaranteed. The existing fault detection schemes between converter stations have the following disadvantages: (1) The existing time domain fault detection schemes are not sensitive enough to high-resistance faults, and terminal high-resistance faults are difficult to identify. (2) The existing frequency domain fault detection schemes have high requirements for sampling elements and have weak recognition capabilities for near-end faults. In summary, the existing fault detection schemes between converter stations construct fault criteria in the time domain or frequency domain alone, resulting in poor reliability. Summary of the invention

[0003] The embodiments of the present invention provide a method, medium and system for fault detection between converter stations for wireless data aggregation, so as to solve the problem of poor reliability of the fault detection scheme between converter stations in the prior art.

[0004] In a first aspect, a method for fault detection between wireless data aggregation converter stations is provided, comprising:

[0005] Collecting the traveling wave voltage of the fault current of the DC transmission line between the converter stations at preset intervals, wherein the traveling wave voltage includes: the traveling wave voltage of the positive line in the DC transmission line and the traveling wave voltage of the negative line in the DC transmission line;

[0006] Calculate the absolute value of the first difference between the traveling wave voltage of the positive line collected this time and the traveling wave voltage of the positive line collected in the previous adjacent time, and the absolute value of the second difference between the traveling wave voltage of the negative line collected this time and the traveling wave voltage of the negative line collected in the previous adjacent time;

[0007] If the absolute value of the first difference and / or the absolute value of the second difference is greater than a first threshold, the positive polarity torsion of the traveling wave voltage of the positive line collected this time and the negative polarity torsion of the traveling wave voltage of the negative line collected this time are calculated respectively;

[0008] The fault location of the DC transmission line between the converter stations is determined according to the magnitude relationship between the positive pole curvature and the negative pole curvature and the second threshold value.

[0009] In a second aspect, a computer-readable storage medium is provided, on which computer program instructions are stored; when the computer program instructions are executed by a processor, the fault detection method between wireless data aggregation converter stations as described in the embodiment of the first aspect is implemented.

[0010] In a third aspect, a fault detection system between wireless data aggregation converter stations is provided, comprising: a computer-readable storage medium as described in the above-mentioned second aspect embodiment.

[0011] In this way, compared with the existing time domain fault detection technology, the embodiment of the present invention is not affected by high-resistance faults and can identify terminal high-resistance faults; compared with the existing frequency domain fault detection technology, the embodiment of the present invention has stronger anti-interference ability and is easy to identify near-end faults; the embodiment of the present invention avoids the communication interference caused by a large number of communication equipment in the converter station, and can be applied to the converter station where multi-protocol wireless data is collected. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0013] Figure 1 is a flow chart of a method for fault detection between wireless data aggregation converter stations according to embodiment 1 of the present invention;

[0014] Figure 2 is a flow chart of a method for fault detection between wireless data aggregation converter stations according to Embodiment 2 of the present invention;

[0015] Figure 3 It is a schematic diagram of the traditional DC transmission system model. DETAILED DESCRIPTION

[0016] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0017] Example 1

[0018] Embodiment 1 of the present invention discloses a method for fault detection between converter stations for wireless data aggregation. The method is applicable to the case where a single fault occurs in the DC transmission line between converter stations during the detection period. Specifically, Figure 1 As shown, the method comprises the following steps:

[0019] Step S101: collecting the traveling wave voltage of the fault current of the DC transmission line between converter stations at preset time intervals.

[0020] The DC transmission line includes a positive line and a negative line. Therefore, the traveling wave voltage includes: the traveling wave voltage of the positive line in the DC transmission line and the traveling wave voltage of the negative line in the DC transmission line. The preset time can be determined based on experience and actual conditions. Specifically, the corresponding equipment can be used to collect the traveling wave voltage.

[0021] Step S102: Calculate the absolute value of the first difference between the traveling wave voltage of the positive line collected this time and the traveling wave voltage of the positive line collected last time, and the absolute value of the second difference between the traveling wave voltage of the negative line collected this time and the traveling wave voltage of the negative line collected last time.

[0022] Step S103: If the absolute value of the first difference and / or the absolute value of the second difference is greater than the first threshold, the positive polarity torsion of the traveling wave voltage of the positive line collected this time and the negative polarity torsion of the traveling wave voltage of the negative line collected this time are calculated respectively.

[0023] Under normal operation, there is no traveling wave voltage. When a DC line fault occurs, the traveling wave voltage amplitude will decrease, and these changes can be used as a criterion for starting fault detection. The first threshold can be preset based on experience and actual conditions. Taking into account various errors such as calculation and measurement, the first threshold is generally set to a value slightly greater than zero. When the traveling wave voltage difference exceeds the set first threshold, fault detection is initiated.

[0024] Specifically, taking the calculation of the absolute value of the first difference corresponding to the positive line as an example, U I+1 It represents the traveling wave voltage of the positive line collected this time, U I represents the traveling wave voltage of the positive line collected in the previous adjacent period, k set1 represents the first threshold, then judge whether |U I+1 -U I |>k set1 .

[0025] As long as one of the absolute value of the first difference corresponding to the positive line and the absolute value of the second difference corresponding to the negative line is greater than the first threshold, the calculation of the torsion is initiated.

[0026] Specifically, the calculation formula for the positive torsion is:

[0027]

[0028] Among them, T P represents the positive torsion, r P ′ represents the first-order derivative of the traveling wave voltage of the positive line, r P ″ represents the second-order derivative of the traveling wave voltage of the positive line, r P ″′ represents the third-order derivative of the traveling wave voltage of the positive line.

[0029] Specifically, the calculation formula for the negative pole torsion is:

[0030] Among them, T N Represents the negative pole torsion, r N ′ represents the first-order derivative of the traveling wave voltage of the negative line, r N ″ represents the second-order derivative of the traveling wave voltage of the negative line, r N ″′ represents the third-order derivative of the traveling wave voltage of the negative line.

[0031] Step S104: determining the fault location of the DC transmission line between converter stations according to the magnitude relationship between the positive pole curvature and the negative pole curvature and the second threshold value.

[0032] Specifically, this step includes the following two situations:

[0033] (1) If the positive pole curvature and / or the negative pole curvature is not greater than the second threshold, it is determined that an intra-regional fault occurs in the DC transmission line between the converter stations.

[0034] That is, k set2 represents the second threshold, satisfying T P ≤k set2 and / or T N ≤k set2 , it is determined that an intra-regional fault occurs on the DC transmission line between converter stations.

[0035] (2) If both the positive pole curvature and the negative pole curvature are greater than the second threshold, it is determined that an out-of-area fault occurs on the DC transmission line between the converter stations.

[0036] That is, k set2 represents the second threshold, satisfying T P >k set2 and T N >k set2 , it is determined that an intra-regional fault occurs on the DC transmission line between converter stations.

[0037] As Figure 3 The model shown in the figure is explained below, and the reason why torsion is used as the criterion is explained below. Figure 3As shown in the figure, this model has two line-commutated converters (LCCs). There are DC filters and current-limiting reactors (L) on both sides of the system.

[0038] When the line occurs Figure 3 When the fault f2 is shown in the area, the time domain and frequency domain formulas of the traveling wave voltage are:

[0039] Time domain: U f11 (t) = K a1 U f1 (1-e-tTa1).

[0040] Frequency domain:

[0041] Among them, K a1 Represents the attenuation ratio coefficient, which is used to describe the degree of traveling wave attenuation. a1 Represents the dispersion time constant, which is used to describe the degree of traveling wave distortion. f1 represents the traveling wave voltage of the fault current. t represents time. s represents a complex number.

[0042] The above-mentioned time domain formula and frequency domain formula of traveling wave voltage both show that the traveling wave is attenuated and distorted. Therefore, the first traveling wave obtained on the LCC side will be bent, which will be more obvious when an external fault occurs.

[0043] When the line occurs Figure 3 When the out-of-zone fault f3 is shown, the time domain and frequency domain formulas of the traveling wave voltage are:

[0044] Time Domain:

[0045] Frequency domain:

[0046] Among them, T aL1 Indicates the attenuation coefficient of line mode voltage. K aL1 Represents the dispersion time constant of the line mode voltage. f2 Represents the traveling wave voltage of the fault current. L2 represents the current limiting inductor. Z c1 represents wave impedance. C represents capacitance. s represents a complex number.

[0047] The above-mentioned time domain formula and frequency domain formula of the traveling wave voltage in the out-of-zone fault show that the influence of the current limiting reactor is much greater than the influence of the line parameters. The traveling wave voltage deviates from the original position in both the time domain and the frequency domain, and the self-correlation can simultaneously reflect the time domain and frequency domain characteristics of the traveling wave voltage. Comparing the time domain and frequency domain formulas of the traveling wave voltage, it can be seen that the voltage self-correlation of the in-zone fault is much stronger than that of the out-of-zone fault.

[0048] The absolute value of the torsion measures the rate of change of the angle between the subnormal vectors of two adjacent points on the curve with respect to the arc length. In the basic differential geometry of three-dimensional curves, the torsion of a curve represents the degree of distortion of the curvature plane. The larger the torsion, the less self-correlation of the waveform, and the smaller the torsion, the greater the self-correlation of the waveform.

[0049] Therefore, according to the above analysis, the embodiment of the present invention can use the torsion to express the voltage self-correlation, and then identify the faults within and outside the zone; when the fault occurs within the zone, the traveling wave voltage self-correlation is stronger, and the torsion is smaller at this time; when the fault occurs outside the zone, the traveling wave voltage self-correlation is weaker, and the torsion is larger at this time. The present invention can use the torsion to simultaneously express the time domain and frequency domain characteristics of the traveling wave voltage.

[0050] In summary, the detection method of Embodiment 1 of the present invention can preliminarily detect whether the fault of the DC transmission line between converter stations is an intra-area fault or an extra-area fault.

[0051] Example 2

[0052] Embodiment 2 of the present invention discloses a method for fault detection between converter stations for wireless data aggregation. The method is applicable to the case where a single fault occurs in the DC transmission line between converter stations within the detection time. Specifically, Figure 2 As shown, the method comprises the following steps:

[0053] Step S201: collecting the traveling wave voltage of the fault current of the DC transmission line between converter stations at preset time intervals.

[0054] Step S202: Calculate the absolute value of the first difference between the traveling wave voltage of the positive line collected this time and the traveling wave voltage of the positive line collected last time, and the absolute value of the second difference between the traveling wave voltage of the negative line collected this time and the traveling wave voltage of the negative line collected last time.

[0055] Step S203: If the absolute value of the first difference and / or the absolute value of the second difference is greater than the first threshold, the positive polarity torsion of the traveling wave voltage of the positive line collected this time and the negative polarity torsion of the traveling wave voltage of the negative line collected this time are calculated respectively.

[0056] Step S204: determining the fault location of the DC transmission line between the converter stations according to the magnitude relationship between the positive pole curvature and the negative pole curvature and the second threshold value.

[0057] Steps S201 to S204 are the same as steps S101 to S104 of embodiment 1, and are not described in detail here. If step S204 determines that the fault is an intra-area fault, the following steps are performed.

[0058] Step S205: Calculate the ratio of the absolute value of the positive polar torsion and the absolute value of the negative polar torsion corresponding to this acquisition.

[0059] Specifically, the calculation formula is:

[0060] Step S206: Determine the fault pole of the DC transmission line between converter stations according to the ratio.

[0061] Specifically, this step includes the following three situations:

[0062] (1) If the ratio is ∞, it is determined that a positive pole fault occurs in the DC transmission line between the converter stations.

[0063] Right now Positive line ground fault on DC transmission line.

[0064] (2) If the ratio is 0, it is determined that a negative pole fault has occurred in the DC transmission line between the converter stations.

[0065] Right now Negative line ground fault on DC transmission line.

[0066] (3) If the ratio is 1, it is determined that a bipolar fault occurs in the DC transmission line between the converter stations.

[0067] Right now Short circuit fault between the two poles of a DC transmission line.

[0068] Fault pole selection is an essential part of fault detection. When a single-pole fault occurs, the traveling wave voltage of the fault pole changes greatly, and its torsion is more obvious. However, there is basically no traveling wave voltage at the non-fault pole, and its torsion is almost zero. Therefore, the present invention uses the torsion ratio as the criterion for fault identification through the above steps.

[0069] In summary, the detection method of Embodiment 2 of the present invention can further detect whether the fault of the DC transmission line between converter stations is a positive pole fault, a negative pole fault or a bipolar fault.

[0070] Example 3

[0071] Embodiment 3 of the present invention discloses a computer-readable storage medium, on which computer program instructions are stored; when the computer program instructions are executed by a processor, a fault detection method between wireless data aggregation converter stations as described in any of the above embodiments 1 and 2 is implemented.

[0072] Example 4

[0073] Embodiment 4 of the present invention discloses a fault detection system for wireless data aggregation converter stations, including: a computer-readable storage medium as described in the above embodiment 3.

[0074] In summary, compared with the existing time domain fault detection technology, the embodiment of the present invention is not affected by high-resistance faults and can identify terminal high-resistance faults; compared with the existing frequency domain fault detection technology, the embodiment of the present invention has stronger anti-interference ability and is easy to identify near-end faults; the embodiment of the present invention avoids the communication interference caused by a large number of communication equipment in the converter station, and can be applied to the converter station where multi-protocol wireless data is collected.

[0075] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A fault detection method for wireless data collection and conversion stations, characterized in that: include: Collecting the traveling wave voltage of the fault current of the DC transmission line between the converter stations at preset intervals, wherein the traveling wave voltage includes: the traveling wave voltage of the positive line in the DC transmission line and the traveling wave voltage of the negative line in the DC transmission line; Calculate the absolute value of the first difference between the traveling wave voltage of the positive line collected this time and the traveling wave voltage of the positive line collected in the previous adjacent time, and the absolute value of the second difference between the traveling wave voltage of the negative line collected this time and the traveling wave voltage of the negative line collected in the previous adjacent time; If the absolute value of the first difference and / or the absolute value of the second difference is greater than a first threshold, the positive polarity torsion of the traveling wave voltage of the positive line collected this time and the negative polarity torsion of the traveling wave voltage of the negative line collected this time are calculated respectively; The fault location of the DC transmission line between the converter stations is determined according to the magnitude relationship between the positive pole curvature and the negative pole curvature and the second threshold value.

2. The fault detection method for wireless data collection converter stations according to claim 1 is characterized in that: The step of determining the fault location of the DC transmission line between the converter stations comprises: If the positive pole curvature and / or the negative pole curvature is not greater than a second threshold, it is determined that an intra-regional fault occurs in the DC transmission line between the converter stations.

3. The fault detection method for wireless data collection converter stations according to claim 1 is characterized in that: The step of determining the fault location of the DC transmission line between the converter stations comprises: If the positive pole curvature and the negative pole curvature are both greater than a second threshold, it is determined that an out-of-region fault occurs in the DC transmission line between the converter stations.

4. The method for fault detection between converter stations for wireless data collection according to claim 2 is characterized in that: If an intra-area fault occurs, after the step of determining the fault location of the DC transmission line between the converter stations, the method further includes: Calculate the ratio of the absolute value of the positive polar torsion and the absolute value of the negative polar torsion corresponding to this acquisition; The fault pole of the DC transmission line between the converter stations is determined according to the ratio.

5. The fault detection method between converter stations for wireless data collection according to claim 4 is characterized in that: The step of determining the fault pole of the DC transmission line between the converter stations according to the ratio comprises: If the ratio is ∞, it is determined that a positive pole fault occurs in the DC transmission line between the converter stations; If the ratio is 0, it is determined that a negative pole fault occurs in the DC transmission line between the converter stations; If the ratio is 1, it is determined that a bipolar fault occurs in the DC transmission line between the converter stations.

6. The method for fault detection between converter stations for wireless data collection according to claim 4 is characterized in that: The calculation formula of the positive pole torsion is: Among them, T P represents the positive torsion, r′ P Represents the first derivative of the traveling wave voltage of the positive line, r″ P Represents the second derivative of the traveling wave voltage of the positive line, r″′ P represents the third-order derivative of the traveling wave voltage of the positive line; The calculation formula of the negative pole torsion is: Among them, T N Represents the negative pole torsion, r′ N Represents the first derivative of the traveling wave voltage of the negative line, r″ N Represents the second derivative of the traveling wave voltage of the negative line, r″′ N Represents the third derivative of the traveling wave voltage of the negative line.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer program instructions; when the computer program instructions are executed by the processor, the method for fault detection between wireless data aggregation converter stations according to any one of claims 1 to 6 is implemented.

8. A fault detection system for wireless data collection and conversion stations, characterized in that: include: The computer readable storage medium of claim 7.

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