Fault identification method of positive sequence direction element, and comparison type distance protection method and device

Abstract

A fault discrimination method of a positive sequence directional element, a comparison distance protection method and device, the fault discrimination method comprising: obtaining three-phase voltage and current phasors at a protection installation point and two-cycle-before three-phase voltage and current phasors; obtaining a voltage mutation variable according to the three-phase voltage and current phasors and the two-cycle-before three-phase voltage and current phasors, and selecting the largest voltage mutation variable as a fault phase; for the fault phase, obtaining a positive sequence voltage and current phase difference mutation variable and a phase-to-phase compensation voltage of the fault phase according to the three-phase voltage and current phasors and the two-cycle-before three-phase voltage and current phasors; and discriminating a fault direction according to the positive sequence voltage and current phase difference mutation variable and the phase-to-phase compensation voltage of the fault phase. The method and device provided in the embodiments of the present application can accurately discriminate the fault phase and the fault direction inside and outside the AC line near the flexible DC, and are beneficial to improving the reliability and sensitivity of the existing comparison distance protection in the phase-to-phase short-circuit fault.

Description

Technical Field

[0001] This invention relates to the field of distance protection technology, specifically to a fault detection method for positive sequence direction elements, a phase comparison type distance protection method and device. Background Technology

[0002] Distance protection is one of the important backup protections for lines. The phase-comparison distance protection based on positive sequence voltage polarization (hereinafter referred to as phase-comparison distance protection) has been widely used due to its advantages of simple principle, clear physical meaning, no dead zone at the output, and good directionality.

[0003] However, the reliability and sensitivity issues of phase-based distance protection have gradually become prominent. Due to the distinct characteristics of flexible DC converters, such as limited fault current and controlled fault current phase, which are quite different from traditional synchronous machines, the phase-based distance protection on the line system side malfunctions when there is a fault outside the back-side zone, and fails to operate when there is a fault inside the output zone on the flexible DC side, which is detrimental to the safe and stable operation of the flexible DC-connected system. Summary of the Invention

[0004] In view of this, the present invention proposes a fault detection method for positive sequence direction elements, a phase comparison distance protection method and device, which aims to solve one or more of the technical problems mentioned in the background section above.

[0005] In a first aspect, embodiments of the present invention provide a fault determination method for a positive-sequence directional element, comprising: acquiring the three-phase voltage and current phasors at the protection installation point and the three-phase voltage and current phasors before two consecutive wave fronts; obtaining voltage mutations based on the three-phase voltage and current phasors and the three-phase voltage and current phasors before two consecutive wave fronts, and selecting the phase with the largest voltage mutation as the fault phase; for the fault phase, obtaining the positive-sequence voltage and current phase difference mutation and the phase-to-phase compensation voltage of the fault phase based on the three-phase voltage and current phasors and the three-phase voltage and current phasors before two consecutive wave fronts; and determining the fault direction based on the positive-sequence voltage and current phase difference mutation and the phase-to-phase compensation voltage of the fault phase.

[0006] Furthermore, based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of the two-week wavefront, the voltage mutation is obtained, and the phase with the largest voltage mutation is selected as the fault phase. This includes calculating the voltage mutation using the following formula.

[0007]

[0008] in, These are three-phase voltage and current phasors. The three-phase voltage and current phasors are given for the two-week wavefront.

[0009] Select The largest one is the faulty phase.

[0010] Furthermore, the abrupt change in the positive sequence voltage and current phase difference is obtained as follows: For the fault phase, the positive sequence voltage and positive sequence current are obtained based on the three-phase voltage and current phasors, and the memory positive sequence voltage and memory positive sequence current are obtained based on the three-phase voltage and current phasors of the two-week wavefront; the real-time positive sequence voltage and current phase difference is obtained based on the positive sequence voltage and positive sequence current, and the memory positive sequence voltage and current phase difference is obtained based on the memory positive sequence voltage and memory positive sequence current; the abrupt change in the positive sequence voltage and current phase difference is obtained by subtracting the real-time positive sequence voltage and current phase difference from the memory positive sequence voltage and current phase difference.

[0011] Furthermore, the interphase compensation voltage of the faulty phase is obtained in the following manner: for the faulty phase, the voltage and current phasors of the faulty phase are obtained based on the three-phase voltage and current phasors; the interphase compensation voltage of the faulty phase is obtained by subtracting the product of the current phasor of the faulty phase and the preset impedance from three times the voltage phasor of the faulty phase.

[0012] Furthermore, the fault direction is determined based on the abrupt change in the positive sequence voltage and current phase difference and the interphase compensation voltage of the faulty phase, including: for the system side of the flexible DC and system tie line, if the absolute value of the abrupt change in the positive sequence voltage and current phase difference is greater than the threshold value of the positive sequence direction element on the system side, and the phase angle of the ratio of the interphase compensation voltage to the polarization voltage of the faulty phase is within a preset range, then it is determined to be a positive direction fault; for the flexible DC and system tie line on the flexible DC side, if the absolute value of the abrupt change in the positive sequence voltage and current phase difference is less than the threshold value of the positive sequence direction element on the flexible DC side, and the phase angle of the ratio of the interphase compensation voltage to the polarization voltage of the faulty phase is within a preset range, then it is determined to be a positive direction fault.

[0013] Furthermore, the phase angle of the ratio of the interphase compensation voltage to the polarization voltage of the faulty phase is within a preset range, including:

[0014]

[0015] in, This is the phase-to-phase compensation voltage for the faulty phase. This is the polarization voltage.

[0016] Secondly, embodiments of the present invention also provide a phase-comparison distance protection method for positive sequence directional elements. When the fault discrimination method for positive sequence directional elements provided in the above embodiments is used to determine that it is a positive direction fault, and the impedance amplitude is less than the preset impedance amplitude, the method includes: constructing a phase-comparison distance protection action equation based on the phase-to-phase compensation voltage of the fault phase, the positive sequence line voltage of the fault phase, and the compensation angle; when the phase-comparison distance protection action equation is satisfied, the fault phase distance protection action output is triggered.

[0017] Furthermore, based on the phase-to-phase compensation voltage of the faulted phase, the positive-sequence line voltage of the faulted phase, and the compensation angle, the phase-to-phase distance protection operating equations are constructed, including: The phase-to-phase distance protection operating equations are constructed as follows:

[0018]

[0019] in, This is the phase-to-phase compensation voltage for the faulty phase. β is the positive sequence line voltage of the faulty phase; β is the compensation angle, the value of which is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current.

[0020] Furthermore, for the flexible DC side of the system tie line, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including: the compensation angle is taken as the first compensation angle γ, which is determined in the following manner:

[0021]

[0022] Where ΔargU1 / I1 is the abrupt change in the phase difference between the positive sequence voltage and current.

[0023] Furthermore, for the flexible DC and system tie-line system side, the compensation angle value is determined based on the range of the abrupt change in the positive sequence voltage-current phase difference, including: the compensation angle is taken as the second compensation angle χ, which is determined in the following manner:

[0024]

[0025] Where ΔargU1 / I1 is the abrupt change in the phase difference between the positive sequence voltage and current.

[0026] Thirdly, embodiments of the present invention also provide a fault discrimination device for a positive-sequence directional element, comprising: an acquisition unit for acquiring three-phase voltage and current phasors at the protection installation point and three-phase voltage and current phasors of two consecutive wavefronts; a first processing unit for obtaining voltage mutations based on the three-phase voltage and current phasors and three-phase voltage and current phasors of two consecutive wavefronts, and selecting the phase with the largest voltage mutation as the fault phase; a second processing unit for obtaining, for the fault phase, a positive-sequence voltage and current phase difference mutation and the phase-to-phase compensation voltage of the fault phase based on the three-phase voltage and current phasors and three-phase voltage and current phasors of two consecutive wavefronts; and a discrimination unit for determining the fault direction based on the positive-sequence voltage and current phase difference mutation and the phase-to-phase compensation voltage of the fault phase.

[0027] Furthermore, the first processing unit is also configured to: calculate the voltage surge using the following formula.

[0028]

[0029] in, These are three-phase voltage and current phasors. The three-phase voltage and current phasors are given for the two-week wavefront.

[0030] Select The largest one is the faulty phase.

[0031] Furthermore, the abrupt change in the positive sequence voltage and current phase difference is obtained as follows: For the fault phase, the positive sequence voltage and positive sequence current are obtained based on the three-phase voltage and current phasors, and the memory positive sequence voltage and memory positive sequence current are obtained based on the three-phase voltage and current phasors of the two-week wavefront; the real-time positive sequence voltage and current phase difference is obtained based on the positive sequence voltage and positive sequence current, and the memory positive sequence voltage and current phase difference is obtained based on the memory positive sequence voltage and memory positive sequence current; the abrupt change in the positive sequence voltage and current phase difference is obtained by subtracting the real-time positive sequence voltage and current phase difference from the memory positive sequence voltage and current phase difference.

[0032] Furthermore, the interphase compensation voltage of the faulty phase is obtained in the following manner: for the faulty phase, the voltage and current phasors of the faulty phase are obtained based on the three-phase voltage and current phasors; the interphase compensation voltage of the faulty phase is obtained by subtracting the product of the current phasor of the faulty phase and the preset impedance from three times the voltage phasor of the faulty phase.

[0033] Furthermore, the discrimination unit is also used to: for the system side of the flexible DC and system interconnect line, if the absolute value of the sudden change in the positive sequence voltage and current phase difference is greater than the threshold value of the positive sequence direction element on the system side, and the phase angle of the ratio of the phase-to-phase compensation voltage to the polarization voltage of the faulty phase is within a preset range, then it is judged as a positive direction fault; for the flexible DC and system interconnect line flexible DC side, if the absolute value of the sudden change in the positive sequence voltage and current phase difference is less than the threshold value of the positive sequence direction element on the flexible DC side, and the phase angle of the ratio of the phase-to-phase compensation voltage to the polarization voltage of the faulty phase is within a preset range, then it is judged as a positive direction fault.

[0034] Furthermore, the phase angle of the ratio of the interphase compensation voltage to the polarization voltage of the faulty phase is within a preset range, including:

[0035]

[0036] in, This is the phase-to-phase compensation voltage for the faulty phase. This is the polarization voltage.

[0037] Fourthly, embodiments of the present invention also provide a phase-comparison distance protection device with a positive sequence directional element. When the fault discrimination device with the positive sequence directional element provided in the above embodiments determines that the fault is in the positive direction and the impedance amplitude is less than the preset impedance amplitude, the device includes: a construction unit, used to construct a phase-comparison distance protection action equation based on the phase-to-phase compensation voltage of the fault phase, the positive sequence line voltage of the fault phase, and the compensation angle; and a protection unit, used to output the fault phase distance protection action when the phase-comparison distance protection action equation is satisfied.

[0038] Furthermore, the building unit is also used to: construct the phase-to-phase distance protection action equation as follows:

[0039]

[0040] in, This is the phase-to-phase compensation voltage for the faulty phase. β is the positive sequence line voltage of the faulty phase; β is the compensation angle, the value of which is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current.

[0041] Furthermore, for the flexible DC side of the system tie line, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including: the compensation angle is taken as the first compensation angle γ, which is determined in the following manner:

[0042]

[0043] Where ΔargU1 / I1 is the abrupt change in the phase difference between the positive sequence voltage and current.

[0044] Furthermore, for the flexible DC and system tie-line system side, the compensation angle value is determined based on the range of the abrupt change in the positive sequence voltage-current phase difference, including: the compensation angle is taken as the second compensation angle χ, which is determined in the following manner:

[0045]

[0046] Where ΔargU1 / I1 is the abrupt change in the phase difference between the positive sequence voltage and current.

[0047] Fifthly, embodiments of the present invention also provide a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, it implements the fault detection method for positive sequence direction elements or the phase-comparison distance protection method for positive sequence direction elements provided in the above embodiments.

[0048] In a sixth aspect, embodiments of the present invention also provide an electronic device, comprising: a processor; a memory for storing executable instructions of the processor; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the fault detection method for positive sequence direction elements or the phase-comparison distance protection method for positive sequence direction elements provided in the above embodiments.

[0049] The fault identification method and device for positive sequence directional elements provided in this invention obtains voltage mutations based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of two consecutive wavefronts, and selects the phase with the largest voltage mutation as the fault phase. For the fault phase, the positive sequence voltage and current phase difference mutation and the phase-to-phase compensation voltage of the fault phase are obtained based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of two consecutive wavefronts, thereby determining the fault direction. This method can accurately identify the fault phase and fault direction inside and outside the flexible DC near-zone AC line, which helps to ensure reliable operation during faults within the zone and improves the reliability and sensitivity of existing phase-to-phase distance protection during phase-to-phase short-circuit faults.

[0050] The phase-comparison distance protection method and device with positive sequence directional element provided in this invention constructs a phase-comparison distance protection action equation based on the phase-to-phase compensation voltage, positive sequence line voltage and compensation angle of the fault phase. When the phase-comparison distance protection action equation is satisfied, the fault phase distance protection action output can accurately distinguish between faults inside and outside the flexible DC near-zone AC line, and reliably operate when there is a fault inside the zone, greatly improving the reliability and sensitivity of existing phase-comparison distance protection in phase-to-phase short-circuit faults. Attached Figure Description

[0051] Figure 1 An exemplary flowchart of a fault detection method for a positive sequence direction element according to an embodiment of the present invention is shown;

[0052] Figure 2 An exemplary flowchart of a phase-comparison distance protection method for a positive sequence direction element according to an embodiment of the present invention is shown;

[0053] Figure 3 A schematic diagram of the phase selection algorithm logic according to an embodiment of the present invention is shown;

[0054] Figure 4 A schematic diagram of a flexible direct-input AC system according to an embodiment of the present invention is shown;

[0055] Figure 5 A schematic diagram showing the phase angle difference between the positive sequence voltage and positive sequence current on both sides of a fault (within the zone) at the flexible straight side outlet of a tie line according to an embodiment of the present invention is provided.

[0056] Figure 6A schematic diagram showing the data of the phase-type distance protection failing to operate when there is a fault (within the zone) at the flexible straight side outlet of the tie line according to an embodiment of the present invention;

[0057] Figure 7 A schematic diagram showing the improvement in operating characteristics when a fault occurs (within the zone) at the flexible straight side outlet of a connecting line according to an embodiment of the present invention is presented.

[0058] Figure 8 A schematic diagram showing the phase angle difference between the positive sequence voltage and positive sequence current on both sides of the tie line outlet F1 (within the zone) according to an embodiment of the present invention is provided.

[0059] Figure 9 A schematic diagram showing the data of the phase-type distance protection malfunction during a busbar fault (outside the zone) on the tie line system side according to an embodiment of the present invention is provided.

[0060] Figure 10 A data diagram illustrating the improved operating characteristics during a busbar fault (outside the zone) in a tie-line system according to an embodiment of the present invention is shown.

[0061] Figure 11 A schematic diagram of a fault detection device for a positive sequence direction element according to an embodiment of the present invention is shown;

[0062] Figure 12 A schematic diagram of a phase-comparison distance protection device with a positive sequence direction element according to an embodiment of the present invention is shown. Detailed Implementation

[0063] Exemplary embodiments of the invention will now be described with reference to the accompanying drawings. However, the invention may be embodied in many different forms and is not limited to the embodiments described herein. These embodiments are provided to fully and completely disclose the invention and to fully convey its scope to those skilled in the art. The terminology used in the exemplary embodiments illustrated in the drawings is not intended to limit the invention. In the drawings, the same units / elements are referred to by the same reference numerals.

[0064] Unless otherwise stated, the terms used herein (including technical terms) have their common meaning as understood by one of ordinary skill in the art. Furthermore, it is understood that terms defined in commonly used dictionaries should be understood to have a meaning consistent with the context of their relevant field, and not to be interpreted as having an idealized or overly formal meaning.

[0065] Figure 1 An exemplary flowchart of a fault detection method for a positive sequence direction element according to an embodiment of the present invention is shown.

[0066] like Figure 1 As shown, the fault diagnosis method includes:

[0067] Step S101: Obtain the three-phase voltage and current phasors at the protection installation point and the three-phase voltage and current phasors of the two-wave front.

[0068] Specifically, the three-phase voltage and current phasors at the current sampling point at the protection installation point are obtained. and the three-phase voltage and current phasors before the two-week wavefront The subscript |0| represents the two cycles preceding the current sampling point.

[0069] Step S102: Based on the three-phase voltage and current phasors and the three-phase voltage and current phasors before the two-week wave front, obtain the voltage mutation amount, and select the phase with the largest voltage mutation amount as the fault phase.

[0070] Further, step S102 includes:

[0071] The voltage surge is calculated using the following formula.

[0072]

[0073] in, These are three-phase voltage and current phasors. The three-phase voltage and current phasors are given for the two-week wavefront.

[0074] Select The largest one is the faulty phase.

[0075] Step S103: For the faulty phase, based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of the two-week wavefront, obtain the abrupt change in the positive sequence voltage and current phase difference and the interphase compensation voltage of the faulty phase.

[0076] Furthermore, the abrupt change in the phase difference between the positive-sequence voltage and current is obtained as follows:

[0077] For the faulty phase, the positive sequence voltage and positive sequence current are obtained from the three-phase voltage and current phasors, and the memory positive sequence voltage and memory positive sequence current are obtained from the three-phase voltage and current phasors of the two-week wavefront.

[0078] Based on the positive sequence voltage and positive sequence current, the real-time positive sequence voltage and current phase difference is obtained, and based on the memory positive sequence voltage and memory positive sequence current, the memory positive sequence voltage and current phase difference is obtained.

[0079] Subtracting the real-time positive-sequence voltage and current phase difference from the memory positive-sequence voltage and current phase difference yields the abrupt change in the positive-sequence voltage and current phase difference.

[0080] Furthermore, the inter-phase compensation voltage of the faulty phase is obtained in the following manner:

[0081] For the faulty phase, the voltage and current phasors of the faulty phase are obtained based on the three-phase voltage and current phasors.

[0082] The interphase compensation voltage of the faulty phase is obtained by subtracting the product of the current phasor of the faulty phase and the preset impedance from the voltage phasor of the faulty phase, which is three times the voltage phasor of the faulty phase.

[0083] Specifically, take the BC phase-to-phase short-circuit fault as an example.

[0084] Calculate positive sequence voltage and positive sequence current

[0085]

[0086] Calculate and memorize positive sequence voltage and current

[0087]

[0088] Calculate the real-time positive sequence voltage and current phase difference ∠U1 / I1:

[0089]

[0090] Calculate and memorize the phase difference ∠U between the positive sequence voltage and current. 1|0| / I 1|0| :

[0091]

[0092] Calculate the abrupt change in phase difference between positive sequence voltage and current, ΔargU1 / I1:

[0093]

[0094] Calculate the interphase compensation voltage:

[0095]

[0096] In the formula, This represents the phase-to-phase compensation voltage for phases BC. The superscript ' indicates the compensation amount. For the voltage phasor of phase BC, Z is the current phasor of phase BC. set This is the preset impedance.

[0097] Step S104: Determine the fault direction based on the sudden change in the phase difference between the positive sequence voltage and current and the interphase compensation voltage of the faulty phase.

[0098] Further, step S104 includes:

[0099] For the system side of the flexible DC and system interconnection line, if the absolute value of the sudden change in the phase difference of the positive sequence voltage and current is greater than the threshold value of the positive sequence direction element on the system side, and the phase angle of the ratio of the phase compensation voltage to the polarization voltage of the faulty phase is within the preset range, then it is judged as a positive direction fault.

[0100] For the flexible DC and system interconnection line, if the absolute value of the sudden change in the phase difference between the positive sequence voltage and current is less than the threshold value of the positive sequence direction element on the flexible DC side, and the phase angle of the ratio of the phase compensation voltage to the polarization voltage of the faulty phase is within the preset range, then it is judged as a positive direction fault.

[0101] Furthermore, the phase angle of the ratio of the interphase compensation voltage to the polarization voltage of the faulty phase is within a preset range, including:

[0102]

[0103] in, This is the phase-to-phase compensation voltage for the faulty phase. This is the polarization voltage.

[0104] Specifically, during a fault, the flexible DC constant power control (or unity power factor control) is the root cause of incorrect operation of the phase-to-phase distance protection. After a fault occurs in the flexible DC near-zone AC system, the positive sequence voltage of the flexible DC converter bus and the positive sequence current provided by the flexible DC converter are basically in phase, causing the virtual power angle of the flexible DC converter to swing, resulting in incorrect operation of the phase-to-phase distance protection.

[0105] The positive-sequence directional element is responsible for determining the fault direction. For reverse-direction faults, the phase-comparison distance protection is blocked. When the system-side protection experiences a forward fault, the fault current flowing through the protection installation point is mainly provided by the system side, and the positive-sequence voltage-current difference abruptly changes from 180° to about 80°, which is a significant change. When the system-side back-side experiences a reverse fault, the fault current flowing through the protection installation point is mainly provided by the flexible DC power supply. Due to the influence of the constant power factor control strategy, the change in |Δarg U1 / I1| is smaller. The active support type flexible DC power supply reactive power support strategy will slightly increase |Δarg U1 / I1| for faults outside the zone, but it is still smaller than |Δarg U1 / I1| for faults within the zone. This characteristic can be used to construct a new type of positive-sequence directional element to solve the reliability problem of phase-comparison distance protection.

[0106] For system-side protection of flexible DC and system interconnection lines, a positive-sequence directional element on the system side is considered a positive-sequence fault when it operates in accordance with the following formula:

[0107]

[0108] In the formula, α1 is the threshold value of the positive-sequence directional element on the system side. For distance segment I, due to fluctuations in the fault transient adjustment process and Fourier algorithm calculation, it is recommended to set it to around 25-30°. For distance segments II and III, it can be set to around 10-15°. The second criterion is that the new directional element is only activated when the phase comparison result is near the action boundary. When the second criterion is not met, the new positive-sequence directional element is disabled. It is important to understand that |Δarg U 1A / I 1A | is equivalent to |Δarg U1 / I1|, where the second A is omitted, and the default A phase is a special phase.

[0109] For the protection of the flexible-direction and system connection line on the flexible-direction side, a positive-sequence directional element on the flexible-direction side is considered to be in the positive direction when it operates in accordance with the following formula:

[0110]

[0111] In the formula, α2 is the threshold value of the straight-side positive sequence direction element.

[0112] For the issue of failure of phase-type distance protection to operate in the dead zone of a positive direction fault exit, an impedance amplitude criterion |Z is added. m |<|Z set When the impedance amplitude criterion and the new positive sequence direction criterion are satisfied simultaneously, the protection will activate.

[0113] The above embodiment obtains the voltage mutation amount based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of two consecutive wavefronts, and selects the phase with the largest voltage mutation amount as the fault phase. For the fault phase, the positive sequence voltage and current phase difference mutation amount and the phase-to-phase compensation voltage of the fault phase are obtained based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of two consecutive wavefronts, thereby determining the fault direction. It can accurately determine the fault phase and fault direction inside and outside the flexible DC near-zone AC line, which helps to operate reliably in the fault zone and is beneficial to improving the reliability and sensitivity of the existing phase-to-phase distance protection in the case of phase-to-phase short-circuit faults.

[0114] Figure 2 An exemplary flowchart of a phase-comparison distance protection method for a positive sequence direction element according to an embodiment of the present invention is shown.

[0115] like Figure 2 As shown, when the fault determination method for the positive sequence directional element provided in the above embodiments determines it to be a positive direction fault, and the impedance amplitude is less than the preset impedance amplitude, the phase-comparison distance protection method includes:

[0116] Step S201: Based on the phase-to-phase compensation voltage of the faulty phase, the positive sequence line voltage of the faulty phase, and the compensation angle, construct the phase-to-phase distance protection action equation;

[0117] Step S202: When the phase-to-phase distance protection action equation is satisfied, the fault phase distance protection action output is triggered.

[0118] Further, step S201 includes:

[0119] The phase-to-phase distance protection action equation is constructed as follows:

[0120]

[0121] in, This is the phase-to-phase compensation voltage for the faulty phase. β is the positive sequence line voltage of the faulty phase; β is the compensation angle, the value of which is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current.

[0122] Furthermore, for the flexible DC side of the system interconnect, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including:

[0123] The compensation angle is taken as the first compensation angle γ, and is determined in the following way:

[0124]

[0125] Where Δarg U1 / I1 is the abrupt change in the phase difference between the positive sequence voltage and current.

[0126] Furthermore, for the flexible DC and system interconnection line system side, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including:

[0127] The compensation angle is taken as the second compensation angle χ, and is determined in the following way:

[0128]

[0129] Where Δarg U1 / I1 is the abrupt change in the phase difference between the positive sequence voltage and current.

[0130] Specifically, taking a phase-to-phase short-circuit fault as an example, the phase-to-phase distance protection operating zone is adjusted according to the relationship between positive sequence voltage and current.

[0131] For the phase-to-phase distance protection on the flexible straight side of the tie line, the improved phase-to-phase distance protection operating equation is as follows:

[0132]

[0133] In the formula, BC represents the positive sequence line voltage. γ is the first compensation angle, and its selection follows these principles:

[0134]

[0135] For the phase-to-phase distance protection on the tie line system side, the improved phase-to-phase distance protection operating equation is as follows:

[0136]

[0137] In the formula, χ is the second compensation angle, which is selected according to the following principles:

[0138]

[0139] When the first compensation angle or the second compensation angle principle is met, the BC phase distance protection action will be activated.

[0140] Figure 3 A schematic diagram of the phase selection algorithm logic according to an embodiment of the present invention is shown. Figure 3 As shown, the AB / CA phase distance protection operation logic is the same as the logic described above.

[0141] The above embodiments construct a phase-to-phase distance protection operating equation based on the phase-to-phase compensation voltage, the positive sequence line voltage of the faulty phase, and the compensation angle. When the phase-to-phase distance protection operating equation is satisfied, the faulty phase distance protection operating output can accurately distinguish between faults inside and outside the flexible DC near-zone AC line, and reliably operate when there is a fault inside the zone, greatly improving the reliability and sensitivity of the existing phase-to-phase distance protection in the case of phase-to-phase short-circuit faults.

[0142] Example 1

[0143] Figure 4 A schematic diagram of a flexible direct-input AC system according to an embodiment of the present invention is shown. To verify the effectiveness of the fault detection method for the positive sequence direction element and the phase-comparison distance protection method provided in an embodiment of the present invention, in such... Figure 4 The simulation system for different types of ground faults inside and outside the AC system is shown in Table 1. The simulation system parameters and settings are shown in Table 2.

[0144] Table 1 Simulation System Parameters and Fixed Values

[0145]

[0146] Table 2. Results of fault identification using new positive sequence direction element and results of improved action zone comparison phase distance protection for faults in both positive and negative directions.

[0147]

[0148]

[0149] Figure 5-10The following diagrams illustrate the following scenarios according to an embodiment of the present invention: a fault on the flexible-vertical side of the tie line outlet (within the zone); a fault on the flexible-vertical side of the tie line outlet (within the zone); a fault on the phase-to-phase distance protection system (within the zone); an improved operating characteristic effect on the flexible-vertical side of the tie line outlet (within the zone); a fault on the tie line outlet F1 (within the zone); a fault on the phase-to-phase distance protection system (outside the zone); and an improved operating characteristic effect on the tie line system side busbar.

[0150] From Table 2 and Figure 5-10 It can be seen that the fault discrimination method for positive sequence direction elements and the phase-comparison distance protection method provided in the embodiments of the present invention can solve the problems of reverse false operation and forward failure to operate of phase-to-phase short circuit faults in the phase-comparison distance protection of flexible DC near-zone AC transmission lines.

[0151] Figure 11 A schematic diagram of a fault detection device for a positive sequence direction element according to an embodiment of the present invention is shown.

[0152] like Figure 11 As shown, the fault detection device includes:

[0153] Acquisition unit 1101 is used to acquire the three-phase voltage and current phasors at the protection installation point and the three-phase voltage and current phasors of two consecutive wavefronts.

[0154] The first processing unit 1102 is used to obtain the voltage change amount based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of the two-week wave front, and select the phase with the largest voltage change amount as the fault phase.

[0155] The second processing unit 1103 is used to obtain the positive sequence voltage and current phase difference abrupt change and the interphase compensation voltage of the faulty phase based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of the two-week wavefront for the faulty phase.

[0156] The discrimination unit 1104 is used to determine the fault direction based on the sudden change in the phase difference between the positive sequence voltage and current and the phase-to-phase compensation voltage of the fault phase.

[0157] Furthermore, the first processing unit 1102 is also used for:

[0158] The voltage surge is calculated using the following formula.

[0159]

[0160] in, These are three-phase voltage and current phasors. The three-phase voltage and current phasors are given for the two-week wavefront.

[0161] Select The largest one is the faulty phase.

[0162] Furthermore, the abrupt change in the phase difference between the positive-sequence voltage and current is obtained as follows:

[0163] For the faulty phase, the positive sequence voltage and positive sequence current are obtained from the three-phase voltage and current phasors, and the memory positive sequence voltage and memory positive sequence current are obtained from the three-phase voltage and current phasors of the two-week wavefront.

[0164] Based on the positive sequence voltage and positive sequence current, the real-time positive sequence voltage and current phase difference is obtained, and based on the memory positive sequence voltage and memory positive sequence current, the memory positive sequence voltage and current phase difference is obtained.

[0165] Subtracting the real-time positive-sequence voltage and current phase difference from the memory positive-sequence voltage and current phase difference yields the abrupt change in the positive-sequence voltage and current phase difference.

[0166] Furthermore, the inter-phase compensation voltage of the faulty phase is obtained in the following manner:

[0167] For the faulty phase, the voltage and current phasors of the faulty phase are obtained based on the three-phase voltage and current phasors.

[0168] The interphase compensation voltage of the faulty phase is obtained by subtracting the product of the current phasor of the faulty phase and the preset impedance from the voltage phasor of the faulty phase, which is three times the voltage phasor of the faulty phase.

[0169] Furthermore, the discrimination unit 1104 is also used for:

[0170] For the system side of the flexible DC and system interconnection line, if the absolute value of the sudden change in the phase difference of the positive sequence voltage and current is greater than the threshold value of the positive sequence direction element on the system side, and the phase angle of the ratio of the phase compensation voltage to the polarization voltage of the faulty phase is within the preset range, then it is judged as a positive direction fault.

[0171] For the flexible DC and system interconnection line, if the absolute value of the sudden change in the phase difference between the positive sequence voltage and current is less than the threshold value of the positive sequence direction element on the flexible DC side, and the phase angle of the ratio of the phase compensation voltage to the polarization voltage of the faulty phase is within the preset range, then it is judged as a positive direction fault.

[0172] Furthermore, the phase angle of the ratio of the interphase compensation voltage to the polarization voltage of the faulty phase is within a preset range, including:

[0173]

[0174] in, This is the phase-to-phase compensation voltage for the faulty phase. This is the polarization voltage.

[0175] The above embodiment obtains the voltage mutation amount based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of two consecutive wavefronts, and selects the phase with the largest voltage mutation amount as the fault phase. For the fault phase, the positive sequence voltage and current phase difference mutation amount and the phase-to-phase compensation voltage of the fault phase are obtained based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of two consecutive wavefronts, thereby determining the fault direction. It can accurately determine the fault phase and fault direction inside and outside the flexible DC near-zone AC line, which helps to operate reliably in the fault zone and is beneficial to improving the reliability and sensitivity of the existing phase-to-phase distance protection in the case of phase-to-phase short-circuit faults.

[0176] Figure 12 A schematic diagram of a phase-comparison distance protection device with a positive sequence direction element according to an embodiment of the present invention is shown.

[0177] like Figure 12 As shown, when the fault detection device for the positive sequence directional element provided in the above embodiments determines that it is a positive direction fault, and the impedance amplitude is less than the preset impedance amplitude, the phase-comparison distance protection device for the positive sequence directional element includes:

[0178] The construction unit 1201 is used to construct the phase-to-phase distance protection action equation based on the phase-to-phase compensation voltage, the positive sequence line voltage of the fault phase, and the compensation angle.

[0179] Protection unit 1202 is used to activate the fault phase distance protection when the phase-to-phase distance protection action equation is satisfied.

[0180] Furthermore, building unit 1201 is also used for:

[0181] The phase-to-phase distance protection action equation is constructed as follows:

[0182]

[0183] in, This is the phase-to-phase compensation voltage for the faulty phase. β is the positive sequence line voltage of the faulty phase; β is the compensation angle, the value of which is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current.

[0184] Furthermore, for the flexible DC side of the system interconnect, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including:

[0185] The compensation angle is taken as the first compensation angle γ, and is determined in the following way:

[0186]

[0187] Where Δarg U1 / I1 is the abrupt change in the phase difference between the positive sequence voltage and current.

[0188] Furthermore, for the flexible DC and system interconnection line system side, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including:

[0189] The compensation angle is taken as the second compensation angle χ, and is determined in the following way:

[0190]

[0191] Where Δarg U1 / I1 is the abrupt change in the phase difference between the positive sequence voltage and current.

[0192] The above embodiments construct a phase-to-phase distance protection operating equation based on the phase-to-phase compensation voltage, the positive sequence line voltage of the faulty phase, and the compensation angle. When the phase-to-phase distance protection operating equation is satisfied, the faulty phase distance protection operating output can accurately distinguish between faults inside and outside the flexible DC near-zone AC line, and reliably operate when there is a fault inside the zone, greatly improving the reliability and sensitivity of the existing phase-to-phase distance protection in the case of phase-to-phase short-circuit faults.

[0193] It should be noted that the apparatus provided in the above embodiments is only illustrated by the division of the above functional modules. In practical applications, the above functions can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. In addition, the apparatus and method embodiments provided in the above embodiments belong to the same concept, and their specific implementation process can be found in the method embodiments, which will not be repeated here.

[0194] This invention also provides a computer-readable storage medium storing a computer program thereon. When the computer program is executed by a processor, it implements the fault detection method for positive sequence direction elements or the phase-comparison distance protection method for positive sequence direction elements provided in the above embodiments.

[0195] This invention also provides an electronic device, including: a processor; a memory for storing processor-executable instructions; the processor being configured to read the executable instructions from the memory and execute the instructions to implement the fault detection method for positive sequence direction elements or the phase-comparison distance protection method for positive sequence direction elements provided in the above embodiments.

[0196] The invention has been described with reference to a few embodiments. However, as will be known to those skilled in the art, and as defined in the appended claims, other embodiments besides those disclosed above fall equivalently within the scope of the invention.

[0197] Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the art, unless otherwise expressly defined herein. All references to “a / the / the [device, component, etc.]” ​​are openly interpreted as at least one instance of said device, component, etc., unless otherwise expressly stated. The steps of any method disclosed herein need not be performed in the exact order disclosed unless explicitly stated otherwise.

[0198] Those skilled in the art will understand that embodiments of the present invention can be provided as methods, systems, or computer program products. Therefore, the present invention can take the form of a completely hardware embodiment, a completely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention can take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0199] This invention is described with reference to flowchart illustrations and / or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the invention. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0200] These computer program instructions may also be stored in a computer-readable storage medium that can direct a computer or other programmable data processing device to function in a particular manner, such that the instructions stored in the computer-readable storage medium produce an article of manufacture including instruction means, which are implemented in a process Figure 1 One or more processes and / or boxes Figure 1 The function specified in one or more boxes.

[0201] These computer program instructions may also be loaded onto a computer or other programmable data processing equipment to cause a series of operational steps to be performed on the computer or other programmable equipment to produce a computer-implemented process, thereby providing instructions that execute on the computer or other programmable equipment for implementing the process. Figure 1 One or more processes and / or boxes Figure 1 The steps of the function specified in one or more boxes.

[0202] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A fault detection method for positive sequence components, characterized in that, include: Obtain the three-phase voltage and current phasors at the protection installation point and the three-phase voltage and current phasors of the two-week wavefront; Based on the three-phase voltage and current phasors and the three-phase voltage and current phasors before two weeks of wave fronts, the voltage mutation is obtained, and the phase with the largest voltage mutation is selected as the fault phase. For the faulty phase, based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of the two-week wavefront, the abrupt change in the positive sequence voltage and current phase difference and the interphase compensation voltage of the faulty phase are obtained. The direction of the fault is determined by the sudden change in the phase difference between the positive sequence voltage and current and the interphase compensation voltage of the faulty phase. The abrupt change in the phase difference between the positive-sequence voltage and current is obtained in the following manner: For the faulty phase, the positive sequence voltage and positive sequence current are obtained from the three-phase voltage and current phasors, and the memory positive sequence voltage and memory positive sequence current are obtained from the three-phase voltage and current phasors of the two-week wavefront. Based on the positive sequence voltage and positive sequence current, the real-time positive sequence voltage and current phase difference is obtained, and based on the memory positive sequence voltage and memory positive sequence current, the memory positive sequence voltage and current phase difference is obtained. Subtracting the real-time positive-sequence voltage and current phase difference from the memory positive-sequence voltage and current phase difference yields the abrupt change in the positive-sequence voltage and current phase difference. The inter-phase compensation voltage of the faulty phase is obtained in the following manner: For the faulty phase, the voltage and current phasors of the faulty phase are obtained based on the three-phase voltage and current phasors. The interphase compensation voltage of the faulty phase is obtained by subtracting the product of the current phasor of the faulty phase and the preset impedance from the voltage phasor of the faulty phase, which is three times the voltage phasor of the faulty phase.

2. The fault diagnosis method according to claim 1, characterized in that, Based on the three-phase voltage and current phasors and the three-phase voltage and current phasors before two consecutive wave fronts, the voltage mutation is obtained, and the phase with the largest voltage mutation is selected as the fault phase, including: The voltage surge is calculated using the following formula. : ； in, These are three-phase voltage and current phasors. The three-phase voltage and current phasors are given for the two-week wavefront. Select The largest one is the faulty phase.

3. The fault diagnosis method according to claim 1, characterized in that, Based on the abrupt change in the phase difference between the positive sequence voltage and current and the inter-phase compensation voltage of the faulted phase, the fault direction is determined, including: For the system side of the flexible DC and system interconnection line, if the absolute value of the sudden change in the phase difference of the positive sequence voltage and current is greater than the threshold value of the positive sequence direction element on the system side, and the phase angle of the ratio of the phase compensation voltage to the polarization voltage of the faulty phase is within the preset range, then it is judged as a positive direction fault. For the flexible DC and system interconnection line, if the absolute value of the sudden change in the phase difference between the positive sequence voltage and current is less than the threshold value of the positive sequence direction element on the flexible DC side, and the phase angle of the ratio of the phase compensation voltage to the polarization voltage of the faulty phase is within the preset range, then it is judged as a positive direction fault.

4. The fault diagnosis method according to claim 3, characterized in that, The phase angle of the ratio of the interphase compensation voltage to the polarization voltage of the faulty phase is within a preset range, including: ； in, This is the phase-to-phase compensation voltage for the faulty phase. This is the polarization voltage.

5. A phase-comparison distance protection method for a positive sequence direction element, characterized in that, When the fault detection method for the positive sequence directional element as described in any one of claims 1-4 is used to determine that it is a positive direction fault, and the impedance amplitude is less than the preset impedance amplitude, it includes: Based on the phase-to-phase compensation voltage of the faulted phase, the positive sequence line voltage of the faulted phase, and the compensation angle, the action equation of the phase-to-phase distance protection is constructed. When the phase-to-phase distance protection action equation is satisfied, the fault phase distance protection action output will be triggered.

6. The phase-comparison distance protection method according to claim 5, characterized in that, Based on the phase-to-phase compensation voltage of the faulted phase, the positive-sequence line voltage of the faulted phase, and the compensation angle, the operating equations for the phase-to-phase distance protection are constructed, including: The phase-to-phase distance protection action equation is constructed as follows: ； in, This is the phase-to-phase compensation voltage for the faulty phase. This is the positive sequence line voltage of the faulty phase; β The compensation angle is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current.

7. The phase-comparison distance protection method according to claim 6, characterized in that, For the flexible DC and the flexible DC side of the system tie line, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including: The compensation angle is taken as the first compensation angle. γ The following method is used to determine it: ； in, This represents the abrupt change in phase difference between positive sequence voltage and current.

8. The phase-comparison distance protection method according to claim 6, characterized in that, For the flexible DC and system interconnection system side, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including: The compensation angle is taken as the second compensation angle. χ The following method is used to determine it: ； in, This represents the abrupt change in phase difference between positive sequence voltage and current.

9. A fault detection device for a positive sequence direction element, characterized in that, include: The acquisition unit is used to acquire the three-phase voltage and current phasors at the protection installation point and the three-phase voltage and current phasors of the two-week wavefronts. The first processing unit is used to obtain the voltage change amount based on the three-phase voltage and current phasors and the three-phase voltage and current phasors before two weeks of wave fronts, and select the phase with the largest voltage change amount as the fault phase. The second processing unit is used to obtain the positive sequence voltage and current phase difference abrupt change and the interphase compensation voltage of the faulty phase based on the three-phase voltage and current phasors and the three-phase voltage and current phasors of the two-week wavefront. The discrimination unit is used to determine the fault direction based on the sudden change in the phase difference between the positive sequence voltage and current and the interphase compensation voltage of the faulty phase. The abrupt change in the phase difference between the positive-sequence voltage and current is obtained in the following manner: For the faulty phase, the positive sequence voltage and positive sequence current are obtained from the three-phase voltage and current phasors, and the memory positive sequence voltage and memory positive sequence current are obtained from the three-phase voltage and current phasors of the two-week wavefront. Based on the positive sequence voltage and positive sequence current, the real-time positive sequence voltage and current phase difference is obtained, and based on the memory positive sequence voltage and memory positive sequence current, the memory positive sequence voltage and current phase difference is obtained. Subtracting the real-time positive-sequence voltage and current phase difference from the memory positive-sequence voltage and current phase difference yields the abrupt change in the positive-sequence voltage and current phase difference. The inter-phase compensation voltage of the faulty phase is obtained in the following manner: For the faulty phase, the voltage and current phasors of the faulty phase are obtained based on the three-phase voltage and current phasors. The interphase compensation voltage of the faulty phase is obtained by subtracting the product of the current phasor of the faulty phase and the preset impedance from the voltage phasor of the faulty phase, which is three times the voltage phasor of the faulty phase.

10. The fault diagnosis device according to claim 9, characterized in that, The first processing unit is further configured to: The voltage surge is calculated using the following formula. : ； in, These are three-phase voltage and current phasors. The three-phase voltage and current phasors are given for the two-week wavefront. Select The largest one is the faulty phase.

11. The fault detection device according to claim 9, characterized in that, The discrimination unit is further configured to: For the system side of the flexible DC and system interconnection line, if the absolute value of the sudden change in the phase difference of the positive sequence voltage and current is greater than the threshold value of the positive sequence direction element on the system side, and the phase angle of the ratio of the phase compensation voltage to the polarization voltage of the faulty phase is within the preset range, then it is judged as a positive direction fault. For the flexible DC and system interconnection line, if the absolute value of the sudden change in the phase difference between the positive sequence voltage and current is less than the threshold value of the positive sequence direction element on the flexible DC side, and the phase angle of the ratio of the phase compensation voltage to the polarization voltage of the faulty phase is within the preset range, then it is judged as a positive direction fault.

12. The fault diagnosis device according to claim 11, characterized in that, The phase angle of the ratio of the interphase compensation voltage to the polarization voltage of the faulty phase is within a preset range, including: ； in, This is the phase-to-phase compensation voltage for the faulty phase. This is the polarization voltage.

13. A phase-comparison distance protection device with a positive sequence direction element, characterized in that, When the fault detection device of the positive sequence direction element as described in any one of claims 9-12 determines that it is a positive direction fault, and the impedance amplitude is less than the preset impedance amplitude, it includes: The construction unit is used to construct the phase-to-phase distance protection action equation based on the phase-to-phase compensation voltage, the positive sequence line voltage of the faulty phase, and the compensation angle. The protection unit is used to activate the fault phase distance protection output when the phase-to-phase distance protection action equation is satisfied.

14. The phase-comparison distance protection device according to claim 13, characterized in that, The building unit is also used for: The phase-to-phase distance protection action equation is constructed as follows: ； in, This is the phase-to-phase compensation voltage for the faulty phase. This is the positive sequence line voltage of the faulty phase; β The compensation angle is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current.

15. The phase-comparison distance protection device according to claim 14, characterized in that, For the flexible DC and the flexible DC side of the system tie line, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including: The compensation angle is taken as the first compensation angle. γ The following method is used to determine it: ； in, This represents the abrupt change in phase difference between positive sequence voltage and current.

16. The phase-comparison distance protection device according to claim 14, characterized in that, For the flexible DC and system interconnection system side, the compensation angle value is determined based on the range of the abrupt change in the phase difference between the positive sequence voltage and current, including: The compensation angle is taken as the second compensation angle. χ The following method is used to determine it: ； in, This represents the abrupt change in phase difference between positive sequence voltage and current.

17. A computer-readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the fault diagnosis method for the positive sequence direction element as described in any one of claims 1-4 or the phase comparison distance protection method for the positive sequence direction element as described in any one of claims 5-8.

18. An electronic device comprising: processor; Memory used to store the processor's executable instructions; The processor is configured to read the executable instructions from the memory and execute the instructions to perform the fault diagnosis method for the positive sequence direction element according to any one of claims 1-4 or the phase-comparison distance protection method for the positive sequence direction element according to any one of claims 5-8.

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