Sequence component-based voltage sag source location method, device and equipment

Abstract

The application discloses a voltage sag source positioning method, device and equipment based on sequence components. The application introduces the symmetrical component method into the current real part polarity method, and has different processing methods for different symmetrical faults. For the asymmetrical fault, the application adopts the negative sequence component variation to calculate and determine the position of the voltage sag source. For the symmetrical fault, the application adopts the positive sequence component variation to calculate and determine the position of the voltage sag source. The application makes up for the deficiency of the current real part polarity method in the asymmetrical fault determination, and the judgment method of the application is simple and effective, and does not need too complex data processing. Only the variation of the fault phase fundamental frequency current sequence component and the variation of the phase angle difference of the current voltage sequence component are needed to calculate the current real part for different types of faults, so that the relative position of the voltage sag source is determined according to the peak value polarity of the current real part about time, and the accuracy is higher compared with the traditional current real part polarity method.

Description

Technical Field

[0001] This invention relates to a method, apparatus, and equipment for locating voltage sag sources based on sequence components, belonging to the field of power system fault location technology. Background Technology

[0002] Voltage sag refers to the phenomenon in a distribution network where the root mean square (RMS) voltage suddenly drops to 90% to 10% of the rated voltage amplitude over a period of time, before recovering to normal. The duration is typically 10ms-1000ms. Voltage sags are relatively common faults in distribution networks, causing equipment or production lines of some sensitive users to shut down, resulting in economic losses. Identifying the upstream and downstream sources of voltage sags is fundamental to voltage sag mitigation and helps power suppliers and users assign responsibility for voltage sag disturbances. The location of the voltage sag source relative to the monitoring point can be divided into upstream and downstream. Typically, the generator side is upstream, and the user side is downstream.

[0003] Voltage sag source location essentially involves determining the relative position of the voltage sag source to the monitoring point. Existing voltage sag source location methods are mainly divided into two categories. The first category comprises a series of location methods derived from disturbance energy and power and their changes. These methods essentially introduce different algorithms to calculate disturbance power and energy and their changes to locate the voltage sag source. The second category comprises a series of location methods derived from changes in distribution network parameters. The real part polarity method of current, the method of determining the slope of the system trajectory, and the real part polarity method of equivalent impedance are classic methods in this second category. However, traditional methods lack the ability to locate fault sources for asymmetric faults. Summary of the Invention

[0004] This invention provides a method, apparatus, and device for locating voltage sag sources based on sequence components, which can be effectively used for locating voltage sag sources under different fault types.

[0005] The technical solution of this invention is: a method for locating voltage sag sources based on sequence components, comprising:

[0006] Acquire three-phase voltage and three-phase current data; based on the three-phase voltage and current data, acquire three-phase fundamental frequency voltage and current data; based on the three-phase fundamental frequency voltage data, acquire the root mean square (RMS) value of the three-phase fundamental frequency voltage; determine the fault type using the RMS value of the three-phase fundamental frequency voltage; wherein, the fault type includes symmetrical faults and asymmetrical faults; for symmetrical faults, based on the three-phase fundamental frequency voltage and current data, acquire the positive sequence component of the fault phase fundamental frequency voltage and the positive sequence component of the fault phase fundamental frequency current; based on the positive sequence voltage... By calculating the phase angle difference of the current and the change in the positive sequence component of the fault phase fundamental frequency current, a curve function of the real part of the current versus time under symmetrical faults is obtained. For asymmetrical faults, based on the three-phase fundamental frequency voltage and current data, the negative sequence components of the fault phase fundamental frequency voltage and current are obtained. Based on the phase angle difference of the negative sequence voltage and current and the change in the negative sequence component of the fault phase fundamental frequency current, a curve function of the real part of the current versus time under asymmetrical faults is obtained. The location of the voltage sag source is determined by the curve of the real part of the current versus time.

[0007] The method of determining the fault type using the root mean square (RMS) values ​​of the three-phase base frequency voltages is as follows: A voltage sag event is determined to have occurred when the RMS value of any one phase's base frequency voltage meets the triggering condition; if all three phases' RMS values ​​meet the triggering condition, it is a symmetrical fault; if any one or two phases' RMS values ​​meet the triggering condition, it is an asymmetrical fault; wherein, the triggering condition for the voltage sag is set to 0.1Un ≤ U. rms ≤0.9Un, where Un is the nominal voltage, U rms This is the root mean square value of the phase voltage.

[0008] For symmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the positive-sequence components of the fault phase fundamental frequency voltage and current are obtained; based on the phase angle difference between the positive-sequence voltage and current and the calculated change in the positive-sequence component of the fault phase fundamental frequency current, a curve function of the change in the real part of the current with respect to time under symmetrical faults is obtained; including: for symmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the positive-sequence components of the fault phase fundamental frequency voltage and current are obtained using the symmetrical component method; the phase angles of the positive-sequence components of the fault phase fundamental frequency voltage and current are extracted through FFT transformation; based on the phase angles of the positive-sequence components of the fault phase fundamental frequency voltage and current, the phase angle difference between the positive-sequence components of the fault phase fundamental frequency voltage and current is obtained, i.e., the phase angle difference between the positive-sequence voltage and current; based on the phase angle difference between the positive-sequence voltage and current and the calculated change in the positive-sequence component of the fault phase fundamental frequency current, a curve function of the change in the real part of the current with respect to time under symmetrical faults is obtained.

[0009] The change in the positive sequence component of the fault phase fundamental frequency current represents the difference between the positive sequence component of the fault phase fundamental frequency current and the positive sequence current when the phase does not experience a voltage dip.

[0010] For asymmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current are obtained; based on the phase angle difference between the negative sequence voltage and current and the calculated change in the negative sequence component of the fault phase fundamental frequency current, a curve function of the change in the real part of the current with respect to time under asymmetrical faults is obtained; including: for asymmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current are obtained using the symmetrical component method; the phase angles of the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current are extracted through FFT transformation; based on the phase angles of the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current, the phase angle difference between the negative sequence components of the fault phase fundamental frequency voltage and the negative sequence components of the current is obtained, i.e., the phase angle difference between the negative sequence voltage and current; based on the phase angle difference between the negative sequence voltage and current and the calculated change in the negative sequence component of the fault phase fundamental frequency current, a curve function of the change in the real part of the current with respect to time under asymmetrical faults is obtained.

[0011] The change in the negative sequence component of the fault phase fundamental frequency current represents the difference between the negative sequence component of the fault phase fundamental frequency current and the negative sequence current when the phase does not experience a voltage dip.

[0012] The method of determining the location of a voltage sag source by means of the curve of the change of the real part of the current with respect to time includes: determining the location of the voltage sag source based on the sign of the first peak of the curve of the real part of the current during the voltage sag period on the curve of the change of the real part of the current with respect to time.

[0013] The location of the voltage sag source is determined by the sign of the first peak of the real part of the current curve during the voltage sag, based on the change curve of the real part of the current over time: For symmetrical faults, if the first peak of the real part of the current during the voltage sag is greater than zero, it indicates that the voltage sag source is downstream of the monitoring point; if the first peak of the real part of the current during the voltage sag is less than zero, it indicates that the voltage sag source is upstream of the monitoring point. For asymmetrical faults, if the first peak of the real part of the current during the voltage sag is less than zero, it indicates that the voltage sag source is downstream of the monitoring point; if the first peak of the real part of the current during the voltage sag is greater than zero, it indicates that the voltage sag source is upstream of the monitoring point.

[0014] According to another aspect of the present invention, a voltage sag source locating device based on sequence components is provided, comprising:

[0015] The first acquisition module is used to acquire three-phase voltage data and three-phase current data; the second acquisition module is used to acquire three-phase fundamental frequency voltage data and three-phase fundamental frequency current data based on the three-phase voltage data and three-phase current data; the third acquisition module is used to acquire the root mean square value of the three-phase fundamental frequency voltage based on the three-phase fundamental frequency voltage data; the first determination module is used to determine the fault type based on the root mean square value of the three-phase fundamental frequency voltage; wherein, the fault type includes symmetrical faults and asymmetrical faults; the fourth acquisition module is used, for symmetrical faults, to acquire the positive sequence component of the fault phase fundamental frequency voltage and the fault phase fundamental frequency based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data. The first module is used to obtain the positive-sequence component of the current; based on the phase angle difference between the positive-sequence voltage and current and the calculated change in the positive-sequence component of the fault phase fundamental frequency current, the real part of the current under symmetrical faults is obtained as a function of time; the second module is used to obtain the negative-sequence component of the fault phase fundamental frequency voltage and the negative-sequence component of the fault phase fundamental frequency current based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data for asymmetrical faults; based on the phase angle difference between the negative-sequence voltage and current and the calculated change in the negative-sequence component of the fault phase fundamental frequency current, the real part of the current under asymmetrical faults is obtained as a function of time; the third module is used to determine the location of the voltage sag source through the change curve of the real part of the current as a function of time.

[0016] According to another aspect of the present invention, a voltage sag source localization device based on sequence components is also provided, the device comprising: a processor and a memory storing computer program instructions; the processor, when executing the program instructions, implements the voltage sag source localization method based on sequence components as described above.

[0017] The beneficial effects of this invention are as follows: This invention introduces the symmetrical component method into the current real part polarity method, providing different processing methods for different symmetrical faults: For asymmetrical faults, this invention uses the change in negative sequence component to calculate and determine the location of the voltage sag source; for symmetrical faults, this invention uses the change in positive sequence component to calculate and determine the location of the voltage sag source. This invention overcomes the shortcomings of the current real part polarity method in determining asymmetrical faults due to insufficient accuracy. Furthermore, the judgment method of this invention is simple and effective, requiring no overly complex data processing. It only needs to calculate the change in the fundamental frequency current sequence component and the change in the phase angle difference between the current and voltage sequence components for different types of faults to calculate the real part of the current. Thus, the relative location of the voltage sag source is determined based on the peak polarity of the current real part change curve over time, resulting in higher accuracy compared to the traditional current real part polarity method. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the process of the present invention;

[0019] Figure 2 This invention relates to a positive-sequence equivalent circuit network for power grids.

[0020] Figure 3 This invention relates to a negative-sequence equivalent circuit network for power grids.

[0021] Figure 4 The upstream and downstream relationships in the power system;

[0022] Figure 5 This is a simulation experiment diagram of a three-phase short-circuit fault according to the present invention;

[0023] Figure 6 This is a simulation diagram of a single-phase grounding fault according to the present invention.

[0024] Figure 7 This is a simulation experiment diagram of a two-phase short-circuit fault according to the present invention;

[0025] Figure 8 This is a simulation experiment diagram of a two-phase ground fault according to the present invention;

[0026] Figure 9 This is a power grid model used in the comparative experiments of different methods in this invention. Detailed Implementation

[0027] The invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of the invention is not limited to the description.

[0028] Example 1: As Figure 1-9 As shown, a voltage sag source localization method based on sequence components includes:

[0029] Acquire three-phase voltage and three-phase current data;

[0030] Based on the three-phase voltage data and three-phase current data, obtain the three-phase fundamental frequency voltage data and three-phase fundamental frequency current data;

[0031] Based on the three-phase fundamental frequency voltage data, obtain the root mean square value of the three-phase fundamental frequency voltage;

[0032] The fault type is determined by the root mean square value of the three-phase fundamental frequency voltage; the fault types include symmetrical faults and asymmetrical faults.

[0033] For symmetrical faults, based on the three-phase fundamental frequency voltage and current data, the positive-sequence components of the fault phase fundamental frequency voltage and current are obtained. Based on the phase angle difference between the positive-sequence voltage and current and the calculated change in the positive-sequence component of the fault phase fundamental frequency current, a curve function of the real part of the current versus time under symmetrical faults is obtained. For asymmetrical faults, based on the three-phase fundamental frequency voltage and current data, the negative-sequence components of the fault phase fundamental frequency voltage and current are obtained. Based on the phase angle difference between the negative-sequence voltage and current and the calculated change in the negative-sequence component of the fault phase fundamental frequency current, a curve function of the real part of the current versus time under asymmetrical faults is obtained.

[0034] The location of the voltage sag source can be determined by the curve of the change of the real part of the current with respect to time.

[0035] Further, the method of determining the fault type based on the root mean square (RMS) values ​​of the three-phase base frequency voltages specifically involves: when the RMS value of any one phase base frequency voltage meets the triggering condition, a voltage sag event is determined to have occurred; if the RMS values ​​of all three phase base frequency voltages meet the triggering condition, it is a symmetrical fault; if the RMS value of any one or two phase base frequency voltages meets the triggering condition, it is an asymmetrical fault; wherein, the triggering condition for the voltage sag is set to 0.1Un ≤ U. rms ≤0.9Un, where Un is the nominal voltage, U rms This is the root mean square value of the phase voltage.

[0036] Furthermore, for symmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the positive-sequence components of the fault phase fundamental frequency voltage and fault phase fundamental frequency current are obtained; based on the phase angle difference between the positive-sequence voltage and current and the calculated change in the positive-sequence component of the fault phase fundamental frequency current, a curve function of the change in the real part of the current with respect to time under symmetrical faults is obtained; this includes: for symmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, using the symmetrical component method to obtain the positive-sequence components of the fault phase fundamental frequency voltage and fault phase fundamental frequency current; extracting the phase angles of the positive-sequence components of the fault phase fundamental frequency voltage and fault phase fundamental frequency current through FFT transformation; obtaining the phase angle difference between the positive-sequence components of the fault phase fundamental frequency voltage and current, i.e., the phase angle difference between the positive-sequence voltage and current, based on the phase angle difference between the positive-sequence components of the fault phase fundamental frequency voltage and fault phase fundamental frequency current; and obtaining a curve function of the change in the real part of the current with respect to time under symmetrical faults based on the phase angle difference between the positive-sequence voltage and current and the calculated change in the positive-sequence component of the fault phase fundamental frequency current.

[0037] Furthermore, the change in the positive sequence component of the fault phase fundamental frequency current represents the difference between the positive sequence component of the fault phase fundamental frequency current and the positive sequence current when the phase does not experience a voltage sag.

[0038] Furthermore, for asymmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current are obtained; based on the phase angle difference between the negative sequence voltage and current and the calculated change in the negative sequence component of the fault phase fundamental frequency current, a curve function of the change in the real part of the current with respect to time under asymmetrical faults is obtained; this includes: for asymmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, using the symmetrical component method to obtain the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current; extracting the phase angles of the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current through FFT transformation; obtaining the phase angle difference between the negative sequence components of the fault phase fundamental frequency voltage and the current, i.e., the phase angle difference between the negative sequence voltage and current, based on the phase angle difference between the negative sequence voltage and current and the calculated change in the negative sequence component of the fault phase fundamental frequency current, a curve function of the change in the real part of the current with respect to time under asymmetrical faults is obtained.

[0039] Furthermore, the change in the negative sequence component of the fault phase fundamental frequency current represents the difference between the negative sequence component of the fault phase fundamental frequency current and the negative sequence current when the phase does not experience a voltage sag.

[0040] Furthermore, determining the location of the voltage sag source by the curve of the change of the real part of the current with respect to time includes: determining the location of the voltage sag source based on the sign of the first peak of the curve of the real part of the current during the voltage sag period on the curve of the change of the real part of the current with respect to time.

[0041] Furthermore, the location of the voltage sag source is determined based on the sign of the first peak value of the real part of the current curve during the voltage sag, according to the curve showing the change of the real part of the current with respect to time: For symmetrical faults, if the first peak value of the real part of the current during the voltage sag is greater than zero, it indicates that the sag source is located downstream of the monitoring point; if the first peak value of the real part of the current during the voltage sag is less than zero, it indicates that the sag source is located upstream of the monitoring point. For asymmetrical faults, if the first peak value of the real part of the current during the voltage sag is less than zero, it indicates that the sag source is located downstream of the monitoring point; if the first peak value of the real part of the current during the voltage sag is greater than zero, it indicates that the sag source is located upstream of the monitoring point.

[0042] Furthermore, based on experimental data, the present invention provides the following optional implementation process:

[0043] Step 1: Install voltage and current measuring devices at the incoming line of the substation, with a sampling frequency of not less than 1kHz, and record the three-phase voltage data and three-phase current data through the voltage and current measuring devices.

[0044] Step 2: Calculate the root mean square value of the recorded voltage sag data;

[0045] Step 3: Determine whether the fault is symmetric or asymmetric by using the root mean square value;

[0046] Step 4: If it is a symmetrical fault, use the symmetrical component method to obtain the fundamental frequency positive sequence voltage and the fundamental frequency positive sequence current of the fault phase; for a symmetrical fault, calculate the change of the fundamental frequency current positive sequence component of the fault phase, calculate the phase difference between the fundamental frequency voltage positive sequence component and the fundamental frequency current positive sequence component of the fault phase, thereby calculating the real part of the current and plotting the curve of the change of the real part of the current with respect to time.

[0047] If it is an asymmetrical fault, obtain the fundamental frequency negative sequence voltage and fundamental frequency negative sequence current of the fault phase; for asymmetrical faults, calculate the change of the negative sequence component of the fundamental frequency current of the fault phase, calculate the phase difference between the negative sequence component of the fundamental frequency voltage and the negative sequence component of the fundamental frequency current of the fault phase, thereby calculating the real part of the current and plotting the curve of the change of the real part of the current with respect to time.

[0048] Step 5: For symmetrical or asymmetrical faults, observe the sign of the first peak of the real part of the current curve during the voltage sag, and determine the location of the voltage sag source accordingly.

[0049] Step 2 above, the calculation of the mean root, includes the following steps:

[0050] Step 2.1: Assume that in this voltage sag event, the three-phase voltage and three-phase current are V... a (n), V b (n), V c (n) and I a (n), I b (n), I c (n), the three-phase fundamental frequency voltage and three-phase fundamental frequency current are extracted by FFT transformation as V a1 (n), V b1 (n), V c1 (n) and I a1 (n), I b1 (n), I c1 (n); where n represents the nth data point within the acquisition period;

[0051] Step 2.2: Calculate the root mean square value of the three-phase fundamental frequency voltage; the specific calculation formula is as follows:

[0052]

[0053]

[0054]

[0055] In the formula: V a1rmsV is the root mean square value of the fundamental frequency voltage of phase A. b1rms V is the root mean square value of the fundamental frequency voltage of phase B. c1rms V is the root mean square value of the C-phase fundamental frequency voltage. a1 (n) represents the nth data point of the fundamental frequency voltage of phase A, V b1 (n) represents the nth data point of the B-phase fundamental frequency voltage, V c1 (n) represents the nth data point of the C-phase fundamental frequency voltage;

[0056] Step 3 above, determining whether a fault is symmetric or asymmetric based on the root mean square value, includes the following steps:

[0057] A voltage sag event is determined to have occurred when the root mean square (RMS) value of any one phase's base frequency voltage meets the triggering condition. If the RMS values ​​of all three phases' base frequency voltages meet the triggering condition, it is a symmetrical fault; if the RMS value of any one or two phases' base frequency voltages meets the triggering condition, it is an asymmetrical fault. The triggering condition for a voltage sag is set as 0.1Un ≤ U. rms ≤0.9Un, where Un is the nominal voltage, U rms This is the root mean square value of the phase voltage;

[0058] The curves showing the change of the real part of the current with respect to time for different fault types in step 4 above include the following steps:

[0059] Step 4.1: If the fault is symmetrical, use the symmetrical component method to obtain the positive-sequence components of the fault phase fundamental frequency voltage and current based on the three-phase fundamental frequency voltage and current data obtained in Step 2.1; if the fault is asymmetrical, use the symmetrical component method to obtain the negative-sequence components of the fault phase fundamental frequency voltage and current based on the three-phase fundamental frequency voltage and current data obtained in Step 2.1. The specific calculation formulas are as follows:

[0060] The following formula assumes phase A is the faulty phase; the others are similar:

[0061]

[0062]

[0063]

[0064]

[0065]

[0066]

[0067] In the formula: I a1 (n) represents the fundamental frequency current of phase A, I b1(n) represents the fundamental frequency current of phase B, I c1 (n) is the fundamental frequency current of phase C, I a2 + (n) represents the positive sequence component of the fundamental frequency current of phase A after a voltage sag, V a2 + (n) represents the positive sequence component of the fundamental frequency voltage of phase A after a voltage dip, I a2 - (n) represents the negative sequence component of the fundamental frequency current of phase A after a voltage sag, V a2 - (n) represents the negative sequence component of the fundamental frequency voltage of phase A after a voltage dip, α is the operator for the phase relationship of phasors, e is the base of the natural logarithm function, and j is the imaginary number;

[0068] Step 4.2: If it is a symmetrical fault, extract the phase angles of the positive-sequence components of the fundamental frequency voltage and the fundamental frequency current of the fault phase using FFT transformation; if it is an asymmetrical fault, extract the phase angles of the negative-sequence components of the fundamental frequency voltage and the fundamental frequency current of the fault phase using FFT transformation; and calculate the phase angle difference between the voltage sequence component and the current sequence component of the fault phase, as shown in the following formula:

[0069] The following formula assumes phase A is the faulty phase; the others are similar:

[0070] Δθ + (n)=∠V a2 + (n)-∠I a2 + (n);

[0071] Δθ - (n)=∠V a2 - (n)-∠I a2 - (n);

[0072] In the formula, ∠V a2 + (n) is the phase angle of the positive sequence component of the fundamental frequency voltage of phase A, ∠V a2 - (n) is the phase angle of the negative sequence component of the fundamental frequency voltage of phase A, ∠I a2 + (n) is the phase angle of the positive sequence component of the fundamental frequency current of phase A, ∠I a2 - (n) is the phase angle of the negative sequence component of the fundamental frequency current of phase A, Δθ + (n) represents the phase angle difference between the positive sequence voltage and current of phase A, Δθ - (n) represents the phase angle difference between the negative sequence voltage and current of phase A;

[0073] Step 4.3: For symmetrical faults, calculate the change in the positive sequence component of the fundamental frequency current of the fault phase, thereby calculating the real part of the current and obtaining the function expression for the change of the real part of the current with respect to time. This allows for the plotting of the curve showing the change of the real part of the current with respect to time under symmetrical faults. For asymmetrical faults, calculate the change in the negative sequence component of the fundamental frequency current of the fault phase, thereby calculating the real part of the current and obtaining the function expression for the change of the real part of the current with respect to time. This allows for the plotting of the curve showing the change of the real part of the current with respect to time under asymmetrical faults. The specific calculation formula is as follows:

[0074] The following formula assumes phase A is the faulty phase; the others are similar:

[0075] ΔI + (n)=I a2 + (n)-I a2pre + ;

[0076] ΔI - (n)=I a2 - (n)-I a2pre - ;

[0077] F(t) + =ΔI + (n)·cos(Δθ + (n));

[0078] F(t) - =ΔI - (n)·cos(Δθ - (n));

[0079] In the above formula, I a2pre + I is the positive sequence current of phase A when no voltage sag occurs. a2pre - The negative sequence current of phase A when no voltage sag occurs, ΔI + (n) represents the change in the positive sequence component of the fundamental frequency current of phase A, ΔI - (n) represents the change in the negative sequence component of the fundamental frequency current of phase A, F(t). + Let F(t) be the function expression for the change curve under symmetrical fault conditions. - This is the function expression for the change curve during asymmetric faults. It should be noted that within one acquisition cycle, the positive-sequence current of phase A without voltage sag and the negative-sequence current of phase A without voltage sag can be obtained by randomly selecting data from any point during the normal operating period before the voltage sag, as recorded by the voltage and current measuring device.

[0080] by Figure 2 Using the positive sequence equivalent circuit diagram as a model, the specific simulation experimental diagram is obtained as follows: Figure 5 As shown; Figure 3 Using the negative sequence equivalent circuit diagram as a model, the specific simulation experimental diagram is obtained as follows: Figure 6-8 As shown in the figure, this simulation experiment sets four types of faults at fault point f: three-phase short circuit fault, single-phase ground fault, two-phase ground fault, and two-phase short circuit fault. The real part curves of the negative sequence current and the real part curves of the positive sequence current at monitoring points M1 and M2 are plotted respectively. That is, under asymmetrical fault conditions, the real part curves of the negative sequence current at monitoring points M1 and M2 are plotted (e.g., ...). Figures 6-8 Under symmetrical fault conditions, plot the real part curves of the positive sequence current at monitoring points M1 and M2 (e.g., Figure 5 The specific discrimination method is shown in steps 5.1 and 5.2 below.

[0081] Determining the location of the voltage sag source in step 5 above includes the following steps:

[0082] Step 5.1: When the fault in the power grid is a symmetrical fault, observe the current real part change curve obtained in step 4. If the first peak value of the current real part during the voltage sag is greater than zero, then the source of the voltage sag is located downstream of the monitoring point. If the first peak value of the current real part during the voltage sag is less than zero, then the source of the voltage sag is located upstream of the monitoring point.

[0083] Step 5.2: When the fault in the power grid is an asymmetrical fault, observe the current real part change curve obtained in step 4. If the first peak value of the current real part during the voltage sag is less than zero, then the source of the voltage sag is located downstream of the monitoring point. If the first peak value of the current real part during the voltage sag is greater than zero, then the source of the voltage sag is located upstream of the monitoring point.

[0084] like Figure 5 As shown in the figure, under symmetrical fault conditions, the first peak value in the real part curve of the positive sequence current at M1 is greater than zero, indicating that the voltage sag source is located downstream of monitoring point M1; at the same time, the first peak value in the real part curve of the positive sequence current at M2 is less than zero, indicating that the voltage sag source is located upstream of monitoring point M2; this is consistent with the actual simulation model, indicating that the present invention can be effectively used to determine the location of the voltage sag source under symmetrical fault conditions.

[0085] like Figure 6 As shown, under a single-phase ground fault, the first peak value in the real part curve of the negative sequence current at M1 is less than zero, indicating that the voltage sag source is located downstream of monitoring point M1; at the same time, the first peak value in the real part curve of the negative sequence current at M2 is greater than zero, indicating that the voltage sag source is located upstream of monitoring point M2; this is consistent with the actual simulation model, indicating that the present invention can be effectively used to determine the location of the voltage sag source under a single-phase ground fault.

[0086] like Figure 7 As shown, under a two-phase short-circuit fault, the first peak value in the real part curve of the negative sequence current at M1 is less than zero, indicating that the voltage sag source is located downstream of monitoring point M1; at the same time, the first peak value in the real part curve of the negative sequence current at M2 is greater than zero, indicating that the voltage sag source is located upstream of monitoring point M2; this is consistent with the actual simulation model, indicating that the present invention can be effectively used to determine the location of the voltage sag source under a two-phase short-circuit fault.

[0087] like Figure 8 As shown, under a two-phase ground fault, the first peak value in the real part curve of the negative sequence current at M1 is less than zero, indicating that the voltage sag source is located downstream of monitoring point M1; at the same time, the first peak value in the real part curve of the negative sequence current at M2 is greater than zero, indicating that the voltage sag source is located upstream of monitoring point M2; this is consistent with the actual simulation model, indicating that the present invention can be effectively used to determine the location of the voltage sag source under a two-phase ground fault.

[0088] Furthermore, with Figure 9 The power grid model shown provides experimental comparison data for the method of this invention, the traditional real part method of current, and the system trajectory slope method. During simulation verification, each method was simulated 90 times. In 67 of these simulations, the root mean square value of the phase voltage at the monitoring point was less than 90% of the nominal voltage, indicating a voltage sag source. Each fault point was simulated sequentially as a single-phase ground fault, a two-phase short-circuit fault, a two-phase ground short-circuit fault, and a three-phase short-circuit fault. The simulation results are shown in Table 1. In the table, "*" indicates that the root mean square value of each phase voltage at the observation point is greater than 90% of the nominal voltage, and is considered as no voltage sag event has occurred; "↓" indicates a different value. Indicates that the fault point is downstream of the monitoring point, indicated by "↑". This indicates that the fault point is upstream of the monitoring point. "↓" and "↑" indicate that the judgment is correct. This indicates an error in judgment. Comparative experiments show that, apart from the method of this invention, the other two methods exhibit errors to varying degrees. Clearly, the accuracy of this invention is significantly higher than the traditional real part of current method and system trajectory slope method.

[0089] Table 1

[0090]

[0091] The presence of positive-sequence, negative-sequence, and zero-sequence components varies depending on the type of short-circuit fault. In symmetrical faults, only the positive-sequence component exists; in asymmetrical faults, both positive and negative-sequence components exist, and a zero-sequence component may also be present. As described above, this invention collects current and voltage data before and during a power grid fault, using the voltage direction as a reference. It extracts the fundamental frequency components of current and voltage using FFT transformation, determines the fault phase based on the root mean square (RMS), calculates the change in the current sequence component of the fault phase using the symmetrical component method, and calculates the change in the voltage and current phase angle difference. This allows for the plotting of a curve showing the real part of the current changing over time. By observing and analyzing the sign of the first peak of the real part curve during the voltage sag, the source of the voltage sag can be located. This method can be used not only for determining the location of voltage sag sources under symmetrical faults but also under asymmetrical faults. By applying the above technical solution, this invention is applicable to locating the source of voltage sags caused by system short-circuit faults, and has the advantages of strong feasibility, simple location of sag sources, and high accuracy.

[0092] Example 2: A voltage sag source location device based on sequence components, comprising: a first acquisition module for acquiring three-phase voltage data and three-phase current data; a second acquisition module for acquiring three-phase fundamental frequency voltage data and three-phase fundamental frequency current data based on the three-phase voltage data and three-phase current data; a third acquisition module for acquiring the root mean square value of the three-phase fundamental frequency voltage based on the three-phase fundamental frequency voltage data; a first determination module for determining the fault type based on the root mean square value of the three-phase fundamental frequency voltage; wherein the fault type includes symmetrical faults and asymmetrical faults; and a fourth acquisition module for, for symmetrical faults, acquiring the fault phase fundamental frequency value based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data. The first module obtains the positive-sequence component of the three-phase fundamental frequency voltage and the positive-sequence component of the fault phase fundamental frequency current. Based on the phase angle difference between the positive-sequence voltage and current and the calculated change in the positive-sequence component of the fault phase fundamental frequency current, a curve function of the real part of the current versus time under a symmetrical fault is obtained. The second module, for asymmetrical faults, obtains the negative-sequence component of the fault phase fundamental frequency voltage and the negative-sequence component of the fault phase fundamental frequency current based on the three-phase fundamental frequency voltage and current data. Based on the phase angle difference between the negative-sequence voltage and current and the calculated change in the negative-sequence component of the fault phase fundamental frequency current, a curve function of the real part of the current versus time under asymmetrical faults is obtained. The third module, for asymmetrical faults, determines the location of the voltage sag source by using the curve of the real part of the current versus time.

[0093] Example 3: A voltage sag source localization device based on sequence components, the device comprising: a processor and a memory storing computer program instructions; the processor, when executing the program instructions, implements the voltage sag source localization method based on sequence components as described above.

[0094] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0095] In the above embodiments of the present invention, the descriptions of each embodiment have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0096] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A method for locating voltage sag sources based on sequence components, characterized in that, include: Acquire three-phase voltage and three-phase current data; Based on the three-phase voltage data and three-phase current data, obtain the three-phase fundamental frequency voltage data and three-phase fundamental frequency current data; Based on the three-phase fundamental frequency voltage data, obtain the root mean square value of the three-phase fundamental frequency voltage; The fault type is determined by the root mean square value of the three-phase fundamental frequency voltage; the fault types include symmetrical faults and asymmetrical faults. For symmetrical faults, based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the positive sequence components of the fundamental frequency voltage and the fundamental frequency current of the fault phase are obtained; based on the phase angle difference between the positive sequence voltage and current and the calculated change of the positive sequence component of the fundamental frequency current of the fault phase, the curve function of the change of the real part of the current with respect to time under symmetrical faults is obtained. For asymmetrical faults, based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the negative sequence components of the fundamental frequency voltage and the fundamental frequency current of the fault phase are obtained; based on the phase angle difference between the negative sequence voltage and current and the calculated change of the negative sequence component of the fundamental frequency current of the fault phase, the curve function of the change of the real part of the current with respect to time under asymmetrical faults is obtained. The location of the voltage sag source can be determined by the curve of the change of the real part of the current with respect to time.

2. The voltage sag source localization method based on sequence components according to claim 1, characterized in that, The method of determining the fault type using the root mean square (RMS) values ​​of the three-phase base frequency voltages is as follows: A voltage sag event is determined to have occurred when the RMS value of any one phase's base frequency voltage meets the triggering condition; if all three phases' RMS values ​​meet the triggering condition, it is a symmetrical fault; if any one or two phases' RMS values ​​meet the triggering condition, it is an asymmetrical fault; wherein, the triggering condition for the voltage sag is set to 0.1Un ≤ U. rms ≤0.9Un, where Un is the nominal voltage, U rms This is the root mean square value of the phase voltage.

3. The voltage sag source localization method based on sequence components according to claim 1, characterized in that, For symmetrical faults, the positive sequence components of the fault phase fundamental frequency voltage and the three-phase fundamental frequency current are obtained based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data. Based on the phase angle difference between the positive-sequence voltage and current and the calculated change in the positive-sequence component of the fundamental frequency current of the fault phase, the curve function of the real part of the current versus time under symmetrical fault conditions is obtained; including: For symmetrical faults, based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the positive sequence components of the fundamental frequency voltage and current of the fault phase are obtained using the symmetrical component method; the phase angles of the positive sequence components of the fundamental frequency voltage and current of the fault phase are extracted by FFT transformation. Based on the phase angle of the positive sequence component of the fundamental frequency voltage of the fault phase and the phase angle of the positive sequence component of the fundamental frequency current of the fault phase, the phase angle difference between the positive sequence component of the fundamental frequency voltage and the positive sequence component of the current of the fault phase is obtained, that is, the phase angle difference between the positive sequence voltage and the current. Based on the phase angle difference between the positive sequence voltage and current and the calculated change in the positive sequence component of the fundamental frequency current of the fault phase, the curve function of the change of the real part of the current with respect to time under symmetrical fault is obtained.

4. The voltage sag source localization method based on sequence components according to claim 3, characterized in that, The change in the positive sequence component of the fault phase fundamental frequency current represents the difference between the positive sequence component of the fault phase fundamental frequency current and the positive sequence current when the phase does not experience a voltage dip.

5. The voltage sag source localization method based on sequence components according to claim 1, characterized in that, For asymmetrical faults, based on three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the negative sequence components of the fault phase fundamental frequency voltage and fault phase fundamental frequency current are obtained; based on the phase angle difference between the negative sequence voltage and current and the calculated change in the negative sequence component of the fault phase fundamental frequency current, a curve function of the change of the real part of the current with respect to time under asymmetrical faults is obtained; including: For asymmetrical faults, based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data, the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current are obtained using the symmetrical component method; the phase angles of the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current are extracted by FFT transformation. Based on the phase angle of the negative sequence component of the fundamental frequency voltage of the fault phase and the phase angle of the negative sequence component of the fundamental frequency current of the fault phase, the phase angle difference between the negative sequence component of the fundamental frequency voltage and the negative sequence component of the current of the fault phase is obtained, that is, the phase angle difference between the negative sequence voltage and the current. Based on the phase angle difference between the negative sequence voltage and current and the calculated change in the negative sequence component of the fundamental frequency current of the fault phase, the curve function of the change of the real part of the current with respect to time under asymmetrical fault is obtained.

6. The voltage sag source localization method based on sequence components according to claim 5, characterized in that, The change in the negative sequence component of the fault phase fundamental frequency current represents the difference between the negative sequence component of the fault phase fundamental frequency current and the negative sequence current when the phase does not experience a voltage dip.

7. The voltage sag source localization method based on sequence components according to claim 1, characterized in that, The method of determining the location of a voltage sag source by means of the curve of the change of the real part of the current with respect to time includes: determining the location of the voltage sag source based on the sign of the first peak of the curve of the real part of the current during the voltage sag period on the curve of the change of the real part of the current with respect to time.

8. The voltage sag source localization method based on sequence components according to claim 7, characterized in that, The location of the voltage sag source is determined by the sign of the first peak of the real part of the current curve during the voltage sag period, based on the change of the real part of the current over time. For the curve of the real part of the current versus time under symmetrical fault, if the first peak value of the real part of the current during the voltage sag is greater than zero, it indicates that the source of the voltage sag is located downstream of the monitoring point. If the first peak value of the real part of the current is less than zero during the voltage sag, it indicates that the source of the voltage sag is located upstream of the monitoring point. For the curve of the real part of the current versus time under asymmetric fault, if the first peak value of the real part of the current during the voltage sag is less than zero, it indicates that the source of the voltage sag is located downstream of the monitoring point. If the first peak value of the real part of the current during the voltage sag is greater than zero, it indicates that the source of the voltage sag is located upstream of the monitoring point.

9. A voltage sag source location device based on sequence components, characterized in that, include: The first acquisition module is used to acquire three-phase voltage data and three-phase current data; The second acquisition module is used to acquire three-phase base frequency voltage data and three-phase base frequency current data based on the three-phase voltage data and three-phase current data; The third acquisition module is used to acquire the root mean square value of the three-phase base frequency voltage based on the three-phase base frequency voltage data; The first determination module is used to determine the fault type by the root mean square value of the three-phase base frequency voltage; wherein the fault type includes symmetrical fault and asymmetrical fault. The fourth acquisition module is used to acquire the positive sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data for symmetrical faults; and to acquire the curve function of the change of the real part of the current with respect to time under symmetrical faults based on the phase angle difference between the positive sequence voltage and current and the calculated change of the positive sequence component of the fault phase fundamental frequency current. The fifth acquisition module is used to acquire the negative sequence components of the fault phase fundamental frequency voltage and the fault phase fundamental frequency current based on the three-phase fundamental frequency voltage and three-phase fundamental frequency current data for asymmetrical faults; and to acquire the curve function of the change of the real part of the current with respect to time under asymmetrical faults based on the phase angle difference between the negative sequence voltage and current and the calculated change of the negative sequence component of the fault phase fundamental frequency current. The second determination module is used to determine the location of the voltage sag source by the curve of the change of the real part of the current with respect to time.

10. A voltage sag source location device based on sequence components, characterized in that: The device includes: a processor and a memory storing computer program instructions; when the processor executes the program instructions, it implements the voltage sag source localization method based on any one of claims 1-8.

Images