A power quality transient event capture method

Abstract

The present application relates to a kind of power quality transient event capture method, the method comprises the following steps: step A, system initialization process;Step B, cycle sampling judgment process;Step C, state machine judgment process.Compared with prior art, the present application has reduced the calculation power consumption required for transient event capture and the corresponding hardware cost and other advantages.

Description

Technical Field

[0001] This invention relates to power quality monitoring technology, and in particular to a method for capturing transient power quality events. Background Technology

[0002] A transient is defined as a physical quantity or phenomenon that changes between two adjacent steady states, with the change time being shorter than the time scale of interest. Power quality transient events are typically used to describe irregular changes in the instantaneous time-domain values ​​of physical quantities such as voltage and current that differ from steady-state processes. Examples include transient overvoltages exhibited by transient voltage waves propagating along lines or circuits caused by lightning surges; periodic spike pulse voltages superimposed on the power frequency voltage exhibited by electrical fast transient pulse groups generated by switching inductive loads; and instantaneous overcurrent phenomena on lines during the connection of high-power capacitive loads and the accompanying voltage waveform defects caused by energy extraction from the grid.

[0003] Voltage transients can cause malfunctions in load devices that are sensitive to power quality. For example, during semiconductor manufacturing operations, voltage transients can cause equipment malfunctions, jeopardizing product quality and production safety. Current transients can induce inrush currents in the windings of parallel or cascaded transformers adjacent to the same line. These inrush currents may cause the inrush current blocking mechanism of the transformer relay protection equipment to fail, leading to malfunctions of the transformer protection and ultimately, power outages.

[0004] Traditional power quality monitoring indicators, such as voltage swells and voltage dips, are typically detected using the half-cycle refreshed root-mean-square (RMS) value method for voltage and the half-cycle refreshed root-mean-square (RMS) value method for current. However, the duration of these transient events is usually shorter than the half-cycle duration of the power frequency supply, which is approximately 10 ms in my country's power grid environment. Traditional detection methods cannot effectively and reliably capture transient current events.

[0005] A search revealed that Chinese patent application number 201911070782.5 discloses a method, apparatus, and device for transient power quality measurement. According to the description, this patented measurement method involves sampling the voltage signal of the circuit under test, performing interpolation, FFT transformation, digital filtering, and zero-crossing point traversal judgment, etc., to eliminate the influence of fundamental and harmonic frequencies on transient voltage measurement, indirectly measuring the peak value and width of the transient signal, and capturing transient voltage events through relevant criteria.

[0006] The aforementioned existing technologies have the following problems in practical applications:

[0007] 1. Accuracy issues caused by resampling: Existing techniques interpolate the basic sampled data and then resample the interpolated results. The interpolated data is distorted for the true signal, as it is virtual reference data created due to insufficient sampling frequency. Because the original data contains both low-frequency and high-frequency signal sample values ​​from the real signal due to frequency aliasing, and the slope change of the time-domain nonlinear signal is also nonlinear, the interpolation result will inevitably deviate from the original signal. The fundamental voltage obtained by performing an FFT transform based on this result will have an error compared to the true fundamental voltage, and this error will propagate all the way to the final transient event criterion calculated.

[0008] 2. Accuracy issues caused by FFT transform: The calculation timescale of transient event parameters in existing technologies is determined by the FFT transform window. Extending or shrinking the FFT transform window using the same method will result in different calculation results. Furthermore, if the transient components do not all fall within the FFT window, spectral leakage will inevitably occur, leading to discrepancies between the calculated results and the actual values. This characteristic also makes it difficult to guarantee the accuracy of transient event capture based on existing technologies.

[0009] 3. Problem of excessive computational load: Existing technologies require real-time interpolation, FFT transformation, digital filtering, and zero-crossing point search on the sampled basic data to capture transient events. The computational load is large, which puts too much pressure on the computing unit. In order to achieve the corresponding computing power, it is necessary to have certain requirements on the performance of the computing unit, resulting in high hardware costs.

[0010] 4. Discrimination error caused by background noise: Existing techniques perform FFT transformation on the interpolated and resampled sample signal to calculate the fundamental frequency parameter. This parameter is then filtered out from the original sample signal to obtain data without the fundamental frequency parameter. This data is then digitally filtered to obtain the final transient component. However, in the real world, the influence of noise cannot be eliminated. This method resamples the original sample signal while simultaneously resampling the noise signal. Errors in the real world are random and disordered, inevitably leading to calculation errors in the transient value and transient duration in the final data obtained from the original sample signal using traditional methods. Summary of the Invention

[0011] The purpose of this invention is to overcome the shortcomings of the existing technology and provide a method for capturing transient power quality events.

[0012] The objective of this invention can be achieved through the following technical solutions:

[0013] According to one aspect of the present invention, a method for capturing transient power quality events is provided, the method comprising the following steps:

[0014] Step A, System initialization process;

[0015] Step B, cyclic sampling and judgment process;

[0016] Step C, state machine judgment process.

[0017] As a preferred technical solution, step A, the system initialization process, specifically includes:

[0018] Step S1: Let N be the sampling point per cycle of the sampling module, n be the current sampling point number, and S be the current sampling point data. n The initial state of the system is denoted as state A, the maximum transient value V is initialized to zero, and the return count value R is initialized. n It is zero;

[0019] Step S2, let e be the discrete filter restoration coefficient when the number of sampling points per cycle is N. N ;

[0020] Step S3, record the system rated value of the currently sampled signal as X. din ;

[0021] Step S4, record the current transient criterion action threshold coefficient as p. t Therefore, the transient criterion action threshold value is p. t X din ;

[0022] Step S5, denote the non-transient criterion threshold as Hq.

[0023] As a preferred technical solution, e in step S2 N The calculation formula is as follows:

[0024]

[0025] As a preferred technical solution, the system rating value in step S3 includes the line rated voltage or the line rated current.

[0026] As a preferred technical solution, the formula for calculating Hq in step S5 of step S2 is as follows:

[0027]

[0028] As a preferred technical solution, step B, the cyclic sampling and judgment process, specifically includes:

[0029] Step S6, for the current sampling point S n With one week of wavefront sampling point S n-N The difference is calculated to obtain the current sampled mutation value, which is the first criterion parameter. The current sampled mutation value is denoted as D. n ;

[0030] Step S7, for the current sampled mutation value D n Compared with the wavefront sampling mutation value D of one week n-N By performing the summation, we obtain the current second criterion parameter, denoted as dD. n ;

[0031] Step S8, change the current second criterion parameter dD n The filter value and the second criterion parameter dD of the half-cycle wavefront n-(N / 2) The filter values ​​are summed to obtain the current non-transient criterion parameter, denoted as SdD. n ;

[0032] Step S9, record the current non-transient criterion accumulation value as Q. n Q n Used for debouncing non-transient judgments;

[0033] Step S10: If the following two formulas involving the first criterion parameter and the second criterion parameter are satisfied simultaneously, then the transient limit violation flag is determined to be "true"; otherwise, the transient limit violation flag is determined to be "false":

[0034]

[0035] Step S11: Update the current maximum transient value, denoted as V.

[0036] As a preferred technical solution, the D n The calculation formula is as follows: D n =S n -S n-N ;

[0037] The dD n The calculation formula is as follows: dD n =D n +D n-N ;

[0038] The SdD n The calculation formula is as follows: SdD n =(dD) n -dD n-1 )+(dD n-(N / 2) -dD n-(N / 2)-1 );

[0039] Where dD n-1 Let dD be the second criterion parameter at sampling point number n-1. n-(N / 2) Let dD be the second criterion parameter at sampling point number n-(N / 2). n-(N / 2)-1 It is the second criterion parameter at the sampling point number n-(N / 2)-1.

[0040] As a preferred technical solution, the Q... n The calculation formula is as follows:

[0041]

[0042] Q n-1 The cumulative value of the non-transient criterion at sampling point number n-1.

[0043] As a preferred technical solution, V is updated using the following formula:

[0044]

[0045] As a preferred technical solution, step C, the state machine judgment process, specifically includes the following steps:

[0046] Step S12: If the current state is initial A and the transient over-limit flag is "true", then it is determined that the transient start state has been entered, denoted as state B, and the current time is t. s This is recorded as the start time of the transient event, and the process returns to the start of the cyclic sampling and judgment process, i.e., step S6.

[0047] Step S13, if the current state is transient startup state B, and the following conditions are met... If the condition is met, the event is judged as a non-transient event, the current state is set to non-transient delayed return state D, and the process returns to the beginning of the cyclic sampling judgment process, i.e., step S6.

[0048] Step S14: If the current state is transient startup state B, and the condition is not met... If the transient limit violation flag is "true", then return to the beginning of the cyclic sampling judgment process, i.e., step S6;

[0049] Step S15: If the current state is transient startup state B, and the condition is not met... If the transient out-of-limit flag is "false", then update the transient event end time, denoted as t. e ; Return the current count value R n Add 1, that is, R n =R n-1 +1; At the same time, set the current state to the transient end state, denoted as state C, and return to the beginning of the cyclic sampling and judgment process, i.e., step S6;

[0050] Step S16, if the current state is the transient end state C, and satisfies If the condition is met, the event will be classified as a non-transient event, and a count value R will be returned. n Clear the current state to a non-transient delayed return state D, and return to the beginning of the cyclic sampling and judgment process, i.e., step S6;

[0051] Step S17: If the current state is the transient end state C, and the condition is not satisfied... If the transient out-of-limit flag is "false", then the current returned count value R is used as the condition. n Determine whether the transient event assessment has been completed. If not... Then R n Increment the value by 1; if the condition is met. The transient event judgment is then complete; the current V value is taken as the maximum transient value of this transient event, and the V value is cleared to zero. The duration of the transient event T = t is then calculated. e -t s The current state is set to the initial state A, and the process returns to the beginning of the cyclic sampling and judgment process, i.e., step S6.

[0052] Step S18, if the current state is the transient end state C, and the condition is not satisfied. If the transient out-of-limit flag is "true", then the current return count value R will be... n Clear the current state to zero, set the current state to transient start state B, and return to the beginning of the cyclic sampling and judgment process, i.e., step S6;

[0053] Step S19: If the current state is a non-transient return state D, and if both the transient limit violation flag is set to "false" and... When the condition is met, the current state is set to the initial state A, and the process returns to the beginning of the cyclic sampling and judgment process, i.e., step S6.

[0054] Step S20: If the current state is a non-transient return state D, and the transient limit violation flag is not simultaneously satisfied with "false" and... If the condition is met, the current state is maintained as state D, and the process returns to the beginning of the cyclic sampling judgment process, i.e., step S6.

[0055] Compared with the prior art, the present invention has the following advantages:

[0056] 1) This invention does not include computationally intensive steps such as multiplication, division, square root extraction, and table lookup in its real-time calculation and judgment process. Compared with traditional methods, it reduces the computing power required to capture transient events and the corresponding hardware costs.

[0057] 2) The accuracy of the transient event duration and transient maximum value obtained using this invention depends on the number of sampling points per cycle of the system. The more sampling points per cycle, the higher the accuracy of the transient event duration and transient maximum value. Compared with traditional methods, the transient event capture function can be flexibly adjusted according to the actual operation, making it more flexible in engineering applications.

[0058] 3) This invention eliminates digital filtering, interpolation, and FFT transform steps, allowing for a more accurate extraction of transient components from the sampled data. Compared to traditional methods, it improves the sensitivity of transient event capture.

[0059] 4) This invention uses a sliding window approach to cyclically store and retrieve various parameters, and provides a judgment result in real time based on the current sampling point number. Compared with traditional methods, this improves the real-time performance of transient event capture.

[0060] 5) This invention uses non-transient criteria to constrain the judgment of transient events, effectively avoiding misjudgment of transient events under steady-state changes in power frequency quantities. Compared with traditional methods, it improves the reliability of transient event capture.

[0061] 6) This invention uses a transient end-return counter mechanism, which can effectively avoid omissions when multiple transient events occur in a short period of time. Compared with traditional methods, it improves the reliability of transient event capture.

[0062] 7) This invention is to a certain extent unaffected by background noise contained in the sampled values. Traditional methods, on the other hand, typically cannot filter out noise and superimpose it onto the true transient components for calculation and judgment. Compared to traditional methods, this invention improves the reliability of transient event capture. Attached Figure Description

[0063] Figure 1 This is a detailed flowchart of the present invention;

[0064] Figure 2 This is a schematic diagram of the sample signal in Embodiment 1 of the present invention;

[0065] Figure 3 This is a schematic diagram of the sample signal in Embodiment 2 of the present invention;

[0066] Figure 4 This is a schematic diagram of the sample signal in Embodiment 3 of the present invention. Detailed Implementation

[0067] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0068] This invention does not distinguish between the sampling signal type; that is, it can be used for related power frequency physical quantities such as voltage or current.

[0069] like Figure 1As shown, the present invention provides a method for capturing transient power quality events, the method comprising the following steps:

[0070] Step A, System initialization process;

[0071] Step B, cyclic sampling and judgment process;

[0072] Step C, state machine judgment process.

[0073] As a preferred technical solution, step A, the system initialization process, specifically includes:

[0074] Step S1: Let N be the sampling point per cycle of the sampling module, n be the current sampling point number, and S be the current sampling point data. n The initial state of the system is denoted as state A, the maximum transient value V is initialized to zero, and the return count value R is initialized. n It is zero;

[0075] Step S2, let e be the discrete filter restoration coefficient when the number of sampling points per cycle is N. N ;

[0076] Step S3, record the system rated value of the currently sampled signal as X. din ;

[0077] Step S4, record the current transient criterion action threshold coefficient as p. t Therefore, the transient criterion action threshold value is p. t X din ;

[0078] Step S5, denote the non-transient criterion threshold as Hq.

[0079] Step B, the cyclic sampling and judgment process, specifically includes:

[0080] Step S6, for the current sampling point S n With one week of wavefront sampling point S n-N The difference is calculated to obtain the current sampled mutation value, which is the first criterion parameter. The current sampled mutation value is denoted as D. n ,in

[0081] Step S7, for the current sampled mutation value D n Compared with the wavefront sampling mutation value D of one week n-N By performing the summation, we obtain the current second criterion parameter, denoted as dD. n ;

[0082] Step S8, change the current second criterion parameter dD n The filter value and the second criterion parameter dD of the half-cycle wavefront n-(N / 2) The filter values ​​are summed to obtain the current non-transient criterion parameter, denoted as SdD. n ;

[0083] Step S9, record the current non-transient criterion accumulation value as Q. n Q n Used for debouncing non-transient judgments;

[0084] Step S10: If the following two formulas involving the first criterion parameter and the second criterion parameter are satisfied simultaneously, then the transient limit violation flag is determined to be "true"; otherwise, the transient limit violation flag is determined to be "false":

[0085]

[0086] Step S11: Update the current maximum transient value, denoted as V.

[0087] Step C, the state machine judgment process, specifically includes the following steps:

[0088] Step S12: If the current state is initial A and the transient over-limit flag is "true", then it is determined that the transient start state has been entered, denoted as state B, and the current time is t. s This is recorded as the start time of the transient event, and the process returns to the start of the cyclic sampling and judgment process, i.e., step S6.

[0089] Step S13, if the current state is transient startup state B, and the following conditions are met... If the condition is met, the event is judged as a non-transient event, the current state is set to non-transient delayed return state D, and the process returns to the beginning of the cyclic sampling judgment process, i.e., step S6.

[0090] Step S14: If the current state is transient startup state B, and the condition is not met... If the transient limit violation flag is "true", then return to the beginning of the cyclic sampling judgment process, i.e., step S6;

[0091] Step S15: If the current state is transient startup state B, and the condition is not met... If the transient out-of-limit flag is "false", then update the transient event end time, denoted as t. e ; Return the current count value R n Add 1, that is, R n =R n-1 +1; At the same time, set the current state to the transient end state, denoted as state C, and return to the beginning of the cyclic sampling and judgment process, i.e., step S6;

[0092] Step S16, if the current state is the transient end state C, and satisfies If the condition is met, the event will be classified as a non-transient event, and a count value R will be returned. nClear the current state to a non-transient delayed return state D, and return to the beginning of the cyclic sampling and judgment process, i.e., step S6;

[0093] Step S17: If the current state is the transient end state C, and the condition is not satisfied... If the transient out-of-limit flag is "false", then the current returned count value R is used as the condition. n Determine whether the transient event assessment has been completed. If not... Then R n Increment the value by 1; if the condition is met. The transient event judgment is then complete; the current V value is taken as the maximum transient value of this transient event, and the V value is cleared to zero. The duration of the transient event T = t is then calculated. e -t s The current state is set to the initial state A, and the process returns to the beginning of the cyclic sampling and judgment process, i.e., step S6.

[0094] Step S18, if the current state is the transient end state C, and the condition is not satisfied. If the transient out-of-limit flag is "true", then the current return count value R will be... n Clear the current state to zero, set the current state to transient start state B, and return to the beginning of the cyclic sampling and judgment process, i.e., step S6;

[0095] Step S19: If the current state is a non-transient return state D, and if both the transient limit violation flag is set to "false" and... When the condition is met, the current state is set to the initial state A, and the process returns to the beginning of the cyclic sampling and judgment process, i.e., step S6.

[0096] Step S20: If the current state is a non-transient return state D, and the transient limit violation flag is not simultaneously satisfied with "false" and... If the condition is met, the current state is maintained as state D, and the process returns to the beginning of the cyclic sampling judgment process, i.e., step S6.

[0097] Example 1

[0098] Single-point transient event capture with superimposed harmonics and noise

[0099] Sample signal description:

[0100] Fundamental frequency: 110;

[0101] Superimposed noise value: 5% fundamental frequency (in this embodiment, a random function is used to randomly select values ​​from 0 to 5.5);

[0102] Superimposed second harmonic value: 8% of the fundamental frequency, initial phase angle random (in this embodiment, it is 81.6° relative to the fundamental frequency);

[0103] The superimposed third harmonic value is 4% of the fundamental frequency, with a random initial phase angle (142.2° relative to the fundamental frequency in this embodiment);

[0104] Superimposed 62nd harmonic value: 8% of fundamental frequency, initial phase angle random (in this embodiment, it is 112.9° relative to the fundamental frequency);

[0105] Superimposed 63rd harmonic value: 4% of fundamental frequency, initial phase angle random (in this embodiment, it is 53.3° relative to the fundamental frequency);

[0106] Maximum transient component: 15% of fundamental frequency;

[0107] Duration of transient components: , where f is the fundamental frequency of the sample signal and N is the number of sampling points per cycle;

[0108] Transient capture function settings:

[0109] System Rating X din 100, transient threshold coefficient p t : 0.1;

[0110] Based on the above description of the sample signals in this embodiment and Figure 2 Sampling point S n It can be seen that the current sample superimposed on the fundamental frequency with random 2nd, 3rd, 62nd, and 63rd harmonics at the initial phase angle, as well as random noise values. Figure 1 The transient components are submerged in harmonics and noise, making them almost undetectable to the human eye.

[0111] Specific implementation method of this method:

[0112] 1) During the system initialization phase, the initial state is denoted as state A. The maximum transient value V is initialized to zero. The initial return count value R is initialized. n The value is zero. The discrete filter direct reduction coefficient is calculated as e using the following formula. N The transient criterion action threshold value is p t X din The threshold for non-transient criteria is Hq.

[0113]

[0114] 2) When the system enters the cyclic sampling judgment phase, D is calculated according to the following formula. n ,dD n 、SdD n Q n .

[0115] D n =S n -S n-N dD n =Dn +D n-N

[0116] SdD n =(dD) n -dD n-1 )+(dD n-(N / 2) -dD n-(N / 2)-1 )

[0117]

[0118] 3) Determine whether the transient over-limit flag is "true" according to the following formula.

[0119]

[0120] 4) In this embodiment, the above Figure 2 It can be seen that at the moment the transient event occurs, the transient limit violation flag is set to "true", and the system is currently in state A. At this time, the current time t is recorded. s At the start of the transient event, record the current V value as the maximum instantaneous value of the transient event, and the system enters state B. Return to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0121] 5) In this embodiment, the above Figure 2 It can be seen that at the end of the transient event, the transient limit violation flag is set to "false", and the system is currently in state B. At this time, the current time t is recorded. e At the end of the transient event, the system enters state C. It then returns to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0122] 6) In this embodiment, the above Figure 2 It can be seen that after the transient event ends During the time period, the system is in state C, and the transient limit violation flag is always set to "false". n After the event ends Always satisfied If the condition is met, the transient event is considered to have ended, and the duration of the transient event, T = t, is recorded. e -t s The system records the current V value as the maximum instantaneous value of the transient event, then clears the V value to zero and returns to state A. It then returns to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0123] This embodiment demonstrates that the present invention can effectively capture single-point transient events under the influence of noise and harmonics.

[0124] Example 2

[0125] Capturing pulse group transient events with superimposed harmonics and noise

[0126] Sample signal description:

[0127] Superimposed noise value: 5% fundamental frequency (in this embodiment, a random function is used to randomly select values ​​from 0 to 5.5);

[0128] Superimposed second harmonic value: 8% of the fundamental frequency, initial phase angle random (6.27° relative to the fundamental frequency in this embodiment);

[0129] The third harmonic value is superimposed: 4% of the fundamental frequency, with a random initial phase angle (in this embodiment, it is 164.8° relative to the fundamental frequency);

[0130] Superimposed 62nd harmonic value: 8% of the fundamental frequency, initial phase angle random (in this embodiment, it is 136.9° relative to the fundamental frequency);

[0131] Superimposed 63rd harmonic value: 4% of fundamental frequency, initial phase angle random (in this embodiment, it is relative to the fundamental frequency of 313.2°);

[0132] Maximum transient component: 20% of the fundamental frequency (in this embodiment, the 100th harmonic is used to simulate a 5kHz electrical fast transient burst).

[0133] Transient component duration: 15ms (in this embodiment, it is divided into two segments: the first segment lasts for 5ms, and after a 2.5ms interval, the second segment lasts for 7.5ms);

[0134] Number of sampling points per wave: N = 1024;

[0135] Transient capture function settings:

[0136] System Rating X din 100, transient threshold coefficient p t : 0.1.

[0137] Based on the above description of the sample signals in this embodiment and Figure 3 Sampling point S n It can be seen that the current sample is superimposed on the fundamental wave with random 2nd, 3rd, 62nd, and 63rd harmonics of the initial phase angle, as well as random noise values.

[0138] Specific implementation method of this method:

[0139] 1) During the system initialization phase, the initial state is denoted as state A. The maximum transient value V is initialized to zero. The initial return count value R is initialized. n The value is zero. The discrete filter direct reduction coefficient is calculated as e using the following formula. N The transient criterion action threshold value is p t X din The threshold for non-transient criteria is Hq.

[0140]

[0141] 2) When the system enters the cyclic sampling judgment phase, D is calculated according to the following formula. n ,dD n 、SdD n Q n .

[0142] D n =S n -S n-N dD n =D n +D n-N

[0143] SdD n =(dD) n -dD n-1 )+(dD n-(N / 2) -dD n-(N / 2)-1 )

[0144]

[0145] 3) Determine whether the transient over-limit flag is "true" according to the following formula.

[0146]

[0147] 4) In this embodiment, the above Figure 3 It can be seen that at the moment the first transient event occurs, the transient limit violation flag is set to "true", and the system is currently in state A. At this time, the current time t is recorded. s At the start of the transient event, record the current V value as the maximum instantaneous value of the transient event, and the system enters state B. Return to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0148] 5) In this embodiment, the above Figure 3 It can be seen that during the 5ms duration of the first transient event, the transient limit violation flag is always set to "true", and the system remains in state B. During this period, the V value is refreshed according to the following formula in each cyclic sampling and judgment process until the end of the first transient event.

[0149]

[0150] 6) In this embodiment, the above Figure 3 It can be seen that at the end of the first transient event, the transient limit violation flag is set to "false", and the system is currently in state B. At this time, the current time t is recorded. e At the end of the transient event, the system enters state C. It then returns to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0151] 7) In this embodiment, the above Figure 3 It can be seen that during the 2.5ms interval before the transient event occurs, the transient limit violation flag is always set to "false", and the system remains in state C. R is calculated using the cyclic sampling judgment process. n The value was not satisfied during the 2.5ms period. The condition remains in effect until the second transient event begins.

[0152] 8) In this embodiment, the above Figure 3 It can be seen that at the beginning of the second transient event, the transient limit violation flag is set to "true", the system is currently in state C, and R... n The value is cleared to zero, the system returns to state B, and refreshes the V value according to the above formula. It then returns to the cyclic sampling judgment process to perform the next sampling and calculate the associated parameters.

[0153] 9) In this embodiment, the above Figure 3 It can be seen that during the 7.5ms duration of the second transient event, the transient limit violation flag is always set to "true", and the system remains in state B. During this period, the V value is refreshed according to the above formula in each cyclic sampling judgment process until the end of the second transient event.

[0154] 10) In this embodiment, the above Figure 3 It can be seen that at the end of the second transient event, the transient limit violation flag is set to "false", and the system is currently in state B. At this time, the current time t is updated. e At the end of the transient event, the system enters state C. It then returns to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0155] 11) In this embodiment, the above Figure 3 It can be seen that after the second transient event ends During the time period, the system remains in state C, and the transient limit violation flag is always set to "false". n After the event ends Always satisfied If the condition is met, the transient event is considered to have ended, and the duration of the transient event, T = t, is recorded. e -t s The system records the current V value as the maximum instantaneous value of the transient event, then clears the V value to zero and returns to state A. It then returns to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0156] This embodiment demonstrates that the method can effectively capture pulse group transient events under the influence of noise and harmonics.

[0157] Example 3

[0158] Superimposed steady-state conditions

[0159] Sample signal description:

[0160] Fundamental frequency: 110 (50Hz power frequency in this embodiment);

[0161] The fundamental wave undergoes steady-state superposition at the trigger point and continues, with an effective value of 11.67 and a phase opposite to that of the fundamental wave.

[0162] Superimposed second harmonic value: 8% of the fundamental frequency, initial phase angle random (in this embodiment, it is 302° relative to the fundamental frequency);

[0163] The superimposed third harmonic value is 4% of the fundamental frequency, and the initial phase angle is random (in this embodiment, it is 170.6° relative to the fundamental frequency).

[0164] Superimposed 62nd harmonic value: 8% of fundamental frequency, initial phase angle random (in this embodiment, it is 192.9° relative to the fundamental frequency);

[0165] Superimposed 63rd harmonic value: 4% fundamental frequency, initial phase angle random (in this embodiment, it is 296.3° relative to the fundamental frequency);

[0166] Transient capture function settings:

[0167] System Rating X din 100, transient threshold coefficient p t : 0.1;

[0168] Based on the above description of the sample signals in this embodiment and the above... Figure 4 Sampling point S n It can be seen that the current sample is superimposed with the 2nd, 3rd, 62nd, and 63rd harmonics with random initial phase angles on the basis of the fundamental wave.

[0169] Specific embodiments of the present invention:

[0170] 1) The method for the period from the start of the steady-state value decrease to the first rising edge of the non-transient flag has been described in detail in Examples 1 and 2. This example mainly focuses on how this method can ensure that transient events are not misjudged under the steady-state change of the sample size. This example describes the process starting from the first rising edge of the non-transient flag after the steady-state value decreases.

[0171] 2) In this embodiment, the above Figure 4 It can be seen that at the first rising edge of the non-transient flag after the steady-state value decreases, the system is currently in state C. If the condition is met, the event that caused the disturbance is determined to be a non-transient event, and the current return count value R is set. n The system is reset to zero and enters non-transient return state D. It then returns to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0172] 3) In this embodiment, the above Figure 4 It can be seen that during the continuous non-transient flag being "true" after the steady-state value decreases, the system remains in state D. Then, at the subsequent non-transient flag being "false," and simultaneously satisfying the condition that the transient limit violation flag is set to "false," the system enters return state A, clearing the V value to zero. It then returns to the cyclic sampling and judgment process to perform the next sampling and calculate the associated parameters.

[0173] This embodiment demonstrates that the method can effectively avoid misjudging steady-state changes in samples as transient events.

[0174] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and these modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for capturing transient power quality events, characterized in that, The method includes the following steps: Step A, System initialization process; Step B, cyclic sampling and judgment process; Step C, state machine judgment process; Step A, the system initialization process, specifically includes: Step S1, record the sampling points of each wave of the sampling module as... The current sampling point number is The current sampling point data is The initial state of the system is recorded as state. Initialize the maximum transient value V to zero, and initialize the return count value. It is zero; Step S2, let the discrete filter restoration coefficient be N for each wave sampling point. ; Step S3, record the system rated value of the currently sampled signal as follows: ; Step S4, record the current transient criterion action threshold coefficient as: Therefore, the transient criterion action threshold value is ; Step S5, denote the non-transient criterion threshold as ; In step S2 The calculation formula is as follows: Step B, the cyclic sampling and judgment process, specifically includes: Step S6, for the current sampling point With one week of wavefront sampling points The difference is calculated to obtain the current sampled mutation value, which is the first criterion parameter. The current sampled mutation value is recorded as [value]. ,in Step S7, for the current sampled mutation value Compared with the wavefront sampling mutation value of one week By performing the summation, we obtain the current second criterion parameter, denoted as... ; Step S8, change the current second criterion parameter The filter value and the second criterion parameter of the half-cycle wavefront The filtered values ​​are summed to obtain the current non-transient criterion parameter, denoted as . ; Step S9, record the current non-transient criterion accumulated value as follows: ,Should Used for debouncing non-transient judgments; Step S10: If the following two formulas involving the first criterion parameter and the second criterion parameter are satisfied simultaneously, then the transient limit violation flag is determined to be "true"; otherwise, the transient limit violation flag is determined to be "false": Step S11, update the current maximum transient value, denoted as ; Step C, the state machine judgment process, specifically includes the following steps: Step S12, if the current state is the initial state If the transient limit violation flag is "true", then the system is determined to have entered the transient initiation state, which is recorded as state . Let the current time be denoted as This is recorded as the start time of the transient event, and the process returns to the start of the cyclic sampling and judgment process, i.e., step S6. Step S13, if the current state is transient startup state And satisfy If the condition is met, the event will be classified as a non-transient event, and the current state will be set to a non-transient delayed return state. And return to the beginning of the cyclic sampling judgment process, i.e., step S6; Step S14, if the current state is transient startup state And not satisfied If the transient limit violation flag is "true", then return to the beginning of the cyclic sampling judgment process, i.e., step S6; Step S15, if the current state is transient startup state And not satisfied If the transient out-of-limit flag is "false", then update the transient event end time, denoted as . ; Return the current count value Add 1, that is Simultaneously, the current state is set to the transient end state, denoted as state C, and the process returns to the beginning of the cyclic sampling and judgment process, i.e., step S6. Step S16, if the current state is the transient end state C, and satisfies If the condition is met, the event will be classified as a non-transient event, and a count value will be returned. Clear to zero, set the current state to a non-transient delayed return state. And return to the beginning of the cyclic sampling judgment process, i.e., step S6; Step S17: If the current state is the transient end state C, and the condition is not satisfied... If the transient out-of-limit flag is "false", then the current returned count value will be used as the condition. Determine whether the transient event assessment has been completed. If not... ,but Increment the value by 1; if the condition is met. Then the transient event judgment is completed; the current... The value is taken as the maximum transient value of this transient event, and the V value is cleared to zero. The duration of the transient event is then calculated. The current state is set to the initial state A, and the process returns to the beginning of the cyclic sampling and judgment process, i.e., step S6. Step S18, if the current state is the transient end state C, and the condition is not satisfied. If the transient out-of-limit flag is "true", then the current return count value will be... Clear the current state to zero, set the current state to transient start state B, and return to the beginning of the cyclic sampling and judgment process, i.e., step S6; Step S19: If the current state is a non-transient return state D, and if both the transient limit violation flag is "false" and... When the condition is met, the current state is set to the initial state A, and the process returns to the beginning of the cyclic sampling and judgment process, i.e., step S6. Step S20: If the current state is a non-transient return state D, and the transient limit violation flag is not simultaneously satisfied with "false" and... If the condition is met, the current state is maintained as state D, and the process returns to the beginning of the cyclic sampling judgment process, i.e., step S6.

2. The method for capturing transient power quality events according to claim 1, characterized in that, The system ratings in step S3 include the line rated voltage or the line rated current.

3. The method for capturing transient power quality events according to claim 1, characterized in that, In step S2, step S5 The calculation formula is as follows: 。 4. The method for capturing transient power quality events according to claim 1, characterized in that, The aforementioned The calculation formula is as follows: ; The The calculation formula is as follows: ; The The calculation formula is as follows: ; in The sampling points are numbered as The second criterion parameter for time, The sampling points are numbered as The second criterion parameter for time, The sampling points are numbered as The second criterion parameter for time.

5. The method for capturing transient power quality events according to claim 1, characterized in that, The aforementioned The calculation formula is as follows: in Sampling point number is The cumulative value of the non-transient criterion at each moment.

6. The method for capturing transient power quality events according to claim 1, characterized in that, The aforementioned Update using the following formula: 。

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